Charging Batteries from Batteries?

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Charging Batteries from Batteries?

Dan Baker
Hello fellow Evlist users,
I have question around charging the battery pack on an EV from a larger
pack of batteries, same voltage. I'm looking to build a stationary solar
array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
batteries, 4 batteries per bank  These are retired but gently used UPS
batteries and I will have about 1200 watts in solar going into a
Morningstar 45 amp solar controller.  I would like to be able to charge my
EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
again, but 4 x 12 volt AGM 133 amp/hr.
My questions for the list:  how do I transfer the charge from the solar
bank to the EV pack?  Can I just use a charge cable directly and the two
banks will equalize?  Or would I need to use a charge controller?   I have
another 45 amp solar controller I could hook from the main battery pack to
the EV pack but I fear the input amps would exceed it?  I remember a while
back someone mentioned they were charging a lawnmower from a truck pack,
wish I could find more info on this.

Thanks in advance for your help and thanks for all the great contributors
on the list, fantastic learning and information!
Dan
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Re: Charging Batteries from Batteries?

EV professor
your reference is from steve at Green Shed Conversions. The process is
called "Dump Charging" and if the voltage is about the same it is very
simple (Akin to " jump-starting" a gas car...)

*Dennis Lee Miles *

*Director   **E.V.T.I. Inc.*

*E-Mail:*  *[hidden email]* <[hidden email]>

   *Phone #* *(863) 944-9913*

Dade City, Florida 33523

 USA




On Sat, Apr 19, 2014 at 5:12 PM, Dan Baker <[hidden email]> wrote:

> Hello fellow Evlist users,
> I have question around charging the battery pack on an EV from a larger
> pack of batteries, same voltage. I'm looking to build a stationary solar
> array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> batteries, 4 batteries per bank  These are retired but gently used UPS
> batteries and I will have about 1200 watts in solar going into a
> Morningstar 45 amp solar controller.  I would like to be able to charge my
> EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> again, but 4 x 12 volt AGM 133 amp/hr.
> My questions for the list:  how do I transfer the charge from the solar
> bank to the EV pack?  Can I just use a charge cable directly and the two
> banks will equalize?  Or would I need to use a charge controller?   I have
> another 45 amp solar controller I could hook from the main battery pack to
> the EV pack but I fear the input amps would exceed it?  I remember a while
> back someone mentioned they were charging a lawnmower from a truck pack,
> wish I could find more info on this.
>
> Thanks in advance for your help and thanks for all the great contributors
> on the list, fantastic learning and information!
> Dan
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Re: Charging Batteries from Batteries?

Dan Baker
Thanks Dennis.  I was wondering if that was all I needed, was concerned the
charge difference between the full pack and a discharged EV pack might be
too great and exceed the charge rate for the AGMs.  I guess I could also
rely on the solar controller to equalize the EV pack when it is plugged in
and the sun is shining.

Cheers
Dan


On Sat, Apr 19, 2014 at 6:31 PM, Dennis Miles <[hidden email]> wrote:

> your reference is from steve at Green Shed Conversions. The process is
> called "Dump Charging" and if the voltage is about the same it is very
> simple (Akin to " jump-starting" a gas car...)
>
> *Dennis Lee Miles *
>
> *Director   **E.V.T.I. Inc.*
>
> *E-Mail:*  *[hidden email]* <[hidden email]>
>
>    *Phone #* *(863) 944-9913*
>
> Dade City, Florida 33523
>
>  USA
>
>
>
>
> On Sat, Apr 19, 2014 at 5:12 PM, Dan Baker <[hidden email]> wrote:
>
> > Hello fellow Evlist users,
> > I have question around charging the battery pack on an EV from a larger
> > pack of batteries, same voltage. I'm looking to build a stationary solar
> > array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> > batteries, 4 batteries per bank  These are retired but gently used UPS
> > batteries and I will have about 1200 watts in solar going into a
> > Morningstar 45 amp solar controller.  I would like to be able to charge
> my
> > EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> > again, but 4 x 12 volt AGM 133 amp/hr.
> > My questions for the list:  how do I transfer the charge from the solar
> > bank to the EV pack?  Can I just use a charge cable directly and the two
> > banks will equalize?  Or would I need to use a charge controller?   I
> have
> > another 45 amp solar controller I could hook from the main battery pack
> to
> > the EV pack but I fear the input amps would exceed it?  I remember a
> while
> > back someone mentioned they were charging a lawnmower from a truck pack,
> > wish I could find more info on this.
> >
> > Thanks in advance for your help and thanks for all the great contributors
> > on the list, fantastic learning and information!
> > Dan
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> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> >
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Re: Charging Batteries from Batteries?

Willie2
On 04/19/2014 05:32 PM, Dan Baker wrote:
> Thanks Dennis.  I was wondering if that was all I needed, was concerned the
> charge difference between the full pack and a discharged EV pack might be
> too great and exceed the charge rate for the AGMs.  I guess I could also
> rely on the solar controller to equalize the EV pack when it is plugged in
> and the sun is shining.
>
I'm sure Steve will weigh in here eventually.  Of course you should be
able to charge the two packs (of nominal equal voltage) together in
parallel.  I think you will find that, if you want to charge one pack
quickly from another, the suppling pack should be at least somewhat
higher voltage.  One or a few extra cells.  Seems like Steve used to
charge his mower (36v?) from his tow truck (96-120v?).
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Re: Charging Batteries from Batteries?

EV professor
When utilizing DUMP Charging, the particular cell chemistry makes a
difference, the PbSO4 Lead acid can be charged with a heavy current but,
lithium can not.  If the packs are at nearly the same voltage the charge
current will be reasonable. If you are charging from a much higher voltage
pack you must limit the charging current, an ideal unit to do this is a DC
motor controller. it will limit the current and maximum charge voltage.
Just pretend the battery to be charged is the motor. ( A coil of wire
--inductor-- may be needed for the controller to work properly depending
upon the controller circuit design. The field winding from a series dc
motor might work...)

*Dennis Lee Miles *

*Director   **E.V.T.I. Inc.*

*E-Mail:*  *[hidden email]* <[hidden email]>

   *Phone #* *(863) 944-9913*

Dade City, Florida 33523

 USA




On Sat, Apr 19, 2014 at 6:42 PM, Willie2 <[hidden email]> wrote:

> On 04/19/2014 05:32 PM, Dan Baker wrote:
>
>> Thanks Dennis.  I was wondering if that was all I needed, was concerned
>> the
>> charge difference between the full pack and a discharged EV pack might be
>> too great and exceed the charge rate for the AGMs.  I guess I could also
>> rely on the solar controller to equalize the EV pack when it is plugged in
>> and the sun is shining.
>>
>>  I'm sure Steve will weigh in here eventually.  Of course you should be
> able to charge the two packs (of nominal equal voltage) together in
> parallel.  I think you will find that, if you want to charge one pack
> quickly from another, the suppling pack should be at least somewhat higher
> voltage.  One or a few extra cells.  Seems like Steve used to charge his
> mower (36v?) from his tow truck (96-120v?).
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/
> group/NEDRA)
>
>
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Re: Charging Batteries from Batteries?

Marco Gaxiola
In reply to this post by Dan Baker
Dan,

 The ideal thing that comes to my mind and think that would be the most efficient is to use a custom dc-dc step-up power supply.  This way you could use the energy stored from the solar battery bank from a wide input voltage range (lets say from 56v to 36v or even 24v) and boost it to your desired voltage. The big the current wanted, the bigger the power supply required.

This could even be a permanent connection that continous transfering the power from one bank to another, but if this is the case; then it means the two packs are inside the EV, right? If so, only a simple relay circuit for your solar Monrning star controller would be needed to switch the charge from one bank to another at several desired conditions. Since both packs are 48volts the solar system array would work fine for charging both.

Other option is: two diodes (one Y diode) can be connected to each pack right from the solar controller, so it can charge both packs at the same time but one pack would not discharge the other (diodes would isolate each others battery) Just like the 'car isolator' a big diode works for ICE cars when they are equipped with big sound systems and use more than one 12v batteries.

I have designed a small current step-up power supply that can provide up to 1.3amp output and up to 60vdc from a 12-24v source, that for a permanent connection would be a great slow charge solution. I could provide those designs if you want to. But is a very slow power transfering. I think bigger powerful solutions can be found on mouser.com, digikey.com etc.

Marco Gaxiola


Enviado desde mi iPhone

> El 19/04/2014, a las 02:12 p.m., Dan Baker <[hidden email]> escribió:
>
> Hello fellow Evlist users,
> I have question around charging the battery pack on an EV from a larger
> pack of batteries, same voltage. I'm looking to build a stationary solar
> array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> batteries, 4 batteries per bank  These are retired but gently used UPS
> batteries and I will have about 1200 watts in solar going into a
> Morningstar 45 amp solar controller.  I would like to be able to charge my
> EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> again, but 4 x 12 volt AGM 133 amp/hr.
> My questions for the list:  how do I transfer the charge from the solar
> bank to the EV pack?  Can I just use a charge cable directly and the two
> banks will equalize?  Or would I need to use a charge controller?   I have
> another 45 amp solar controller I could hook from the main battery pack to
> the EV pack but I fear the input amps would exceed it?  I remember a while
> back someone mentioned they were charging a lawnmower from a truck pack,
> wish I could find more info on this.
>
> Thanks in advance for your help and thanks for all the great contributors
> on the list, fantastic learning and information!
> Dan
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>
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Re: Charging your EV pack from other batteries?

brucedp5
This post was updated on .
In reply to this post by Dan Baker
I have seen drivers charge their pack from another pack.

The first instance was when I heard of a couple in the East SF Bay EAA
Chapter, the Cornell's, who both drove EVs. Talk about getting the most
out of the $ they spent on a pack, when a pack was replaced because its
range did not suit their needs, the batteries that still had life in
them were stored in the garage, and kept charged from the solar array on
their roof (this was at a time when there were no solar incentives, and
the Cornell's were way ahead of everyone else. Their roof solar would be
thought of as common place by today's standards).

When one of them got home, they would recharge their EV off the older
pack which had been recharged from solar electrons. The current they
used to recharge their pack was low, so I would not call it a dump
charge. At that time, a dump charge was what the racers were doing at
the track with high currents (like level-3 power), to get back out to
race on the track (APS racing).

The other experience was at high current levels, so you could call it a
dump charge of sorts. In both cases, the effort to transfer the power
from one pack to the other was a manual one, where the human brain was
the smart charger. They each used a source pack that was at an
incrementally higher voltage (higher than a destination pack voltage).

The example is when I hung out with John Wayland at a Sacramento Raceway
nedra.com EVent. His White Zombie at the time I believe had the smaller 12V
Johnson Controls agms. His older pack that used to be in his EV were made
up of Optima yellow top agms. When he came in to his pit location after
doing his run, he would measure his EV pack voltage, and match that plus
add one more 12V agm. Then connect the slightly higher voltage old pack to
his EV's partially spent pack. As the dump current decreased, he would
add another 12V agm to bump up the current. He knew from experience when
to do this so as to not push too much recharge current, and to not waste
time on a lower, slower recharge current.

When John's EV pack had neared its finishing voltage, when racing
he pushed/goosed it a little, forcing a higher than normal finishing
current into hisEV's pack. This caused his EV's agm pack to steam
some of the electrolyte. John said he did this on purpose because a
hot pack performed better (one could liken that thinking to:
prematurely aging/destroying his EV's agm pack just so he can get
a better race time, to what the ice heads to when they push their
ice beyond red-line). When he left to go get in line to race again, he
had a genset pushing power back into the old Optima set of batteries
that was in his support vehicle.

I've heard of drivers of today using a controller to push the power from
one pack to another. It still would require a human to incrementally
bump the current up as the pack charged, but no batteries had to be
added, you could start out by using the highest source pack voltage.


{brucedp.150m.com}



-
On Sat, Apr 19, 2014, at 02:12 PM, Dan Baker wrote:
> Hello fellow Evlist users,
> I have question around charging the battery pack on an EV from a larger
> pack of batteries, same voltage. I'm looking to build a stationary solar
> array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> batteries, 4 batteries per bank  These are retired but gently used UPS
> batteries and I will have about 1200 watts in solar going into a
> Morningstar 45 amp solar controller.  I would like to be able to charge
> my
> EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> again, but 4 x 12 volt AGM 133 amp/hr.
> My questions for the list:  how do I transfer the charge from the solar
> bank to the EV pack?  Can I just use a charge cable directly and the two
> banks will equalize?  Or would I need to use a charge controller?   I
> have
> another 45 amp solar controller I could hook from the main battery pack
> to
> the EV pack but I fear the input amps would exceed it?  I remember a
> while
> back someone mentioned they were charging a lawnmower from a truck pack,
> wish I could find more info on this ...
-

--
http://www.fastmail.fm - Or how I learned to stop worrying and
                          love email again

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Re: Charging your EV pack from other batteries?

Dan Baker
Thank you Bruce, Dennis, Willie and Marco for the info.  So it sounds like
a charge from batteries of similar voltage could work, although the charge
wouldn't be very robust/complete depending on the difference in state of
charge between the packs?  I expect the best charge would be if the solar
pack is fully charged and the PV array is under full sunlight conditions
and the least would be at night and both packs have been partially drained?
 Like most leisure craft my boats spend most of the time parked at dock so
I would expect the EV pack would likely be connected under the PV pack
being charged most of the time.  Dump charging or high speed charging
really isn't necessary for my use but a quicker than the normal 6-10 hour
charge would be nice.  I guess I could also use an invertor to convert the
48 volts to 120 volts and plug in my regular wall charger to have a
complete charge (cheaply make a high amp step up circuit like Marco
suggested) but that sounds much more terribly inefficient. :-(

Cheers
Dan


On Sat, Apr 19, 2014 at 10:41 PM, Bruce EVangel Parmenter <
[hidden email]> wrote:

> I have seen drivers charge their pack from another pack.
>
> The first instance was when I heard of a couple in the East SF Bay EAA
> Chapter, the Cornell's, who both drove EVs. Talk about getting the most
> out of the $ they spent on a pack, when a pack was replaced because its
> range did not suit their needs, the batteries that still had life in
> them were stored in the garage, and kept charged from the solar array on
> their roof (this was at a time when there were no solar incentives, and
> the Cornell's were way ahead of everyone else. Their roof solar would be
> thought of as common place by today's standards).
>
> When one of them got home, they would recharge their EV off the older
> pack which had been recharged from solar electrons. The current they
> used to recharge their pack was low, so I would not call it a dump
> charge. At that time, a dump charge was what the racers were doing at
> the track with high currents (like level-3 power), to get back out to
> race on the track (APS racing).
>
> The other experience was at high current levels, so you could call it a
> dump charge of sorts. In both cases, the effort to transfer the power
> from one pack to the other was a manual one, where the human brain was
> the smart charger. They each used a source pack that was at an
> incrementally higher voltage (higher than a destination pack voltage).
>
> The example is when I hung out with John Wayland at a Sacramento Raceway
> nedra.com EVent. His White Zombie at the time I believe had the smaller
> Jonson Controls agms. His older pack that used to be in his EV were made
> up of Optima yellow top agms. When he came in to his pit location after
> doing his run, he would measure his pack voltage, and match that plus
> one more 12V agm. Then connect the slightly higher voltage old pack to
> his EV's partially spent pack. As the dump current decreased, he would
> add another 12 agm to bump up the current. He knew from experience when
> to do this so as to not push too much dump current, and to not waste
> time on a lower, slower dump current.
>
> When John's EV pack had reached the finishing voltage, he pushed/goosed
> it a little, forcing a higher than normal finishing current into his
> EV's pack. This caused his EV's agm pack to steam some of the
> electrolyte. John said he did this on purpose because his hot pack
> performed better (one could like that thinking: prematurely
> aging/destroying his EV's agm pack just so he can get a better race
> time, to what the ice heads to when they push their ice beyond
> red-line).  After he left to go get in line to race again, he had a
> genset pushing power into the old Optima set of batteries that was in
> his support vehicle.
>
> I've heard of drivers of today using a controller to push the power from
> one pack to another. IT still would require a human to incrementally
> bump the current up as the pack charged, but no batteries had to be
> added, you could start out by using the highest source pack voltage.
>
>
> {brucedp.150m.com}
>
>
>
> -
> On Sat, Apr 19, 2014, at 02:12 PM, Dan Baker wrote:
> > Hello fellow Evlist users,
> > I have question around charging the battery pack on an EV from a larger
> > pack of batteries, same voltage. I'm looking to build a stationary solar
> > array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> > batteries, 4 batteries per bank  These are retired but gently used UPS
> > batteries and I will have about 1200 watts in solar going into a
> > Morningstar 45 amp solar controller.  I would like to be able to charge
> > my
> > EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> > again, but 4 x 12 volt AGM 133 amp/hr.
> > My questions for the list:  how do I transfer the charge from the solar
> > bank to the EV pack?  Can I just use a charge cable directly and the two
> > banks will equalize?  Or would I need to use a charge controller?   I
> > have
> > another 45 amp solar controller I could hook from the main battery pack
> > to
> > the EV pack but I fear the input amps would exceed it?  I remember a
> > while
> > back someone mentioned they were charging a lawnmower from a truck pack,
> > wish I could find more info on this ...
> -
>
> --
> http://www.fastmail.fm - Or how I learned to stop worrying and
>                           love email again
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: Charging Batteries from Batteries?

Lee Hart
In reply to this post by Dan Baker
Dan Baker wrote:
> I have question around charging the battery pack on an EV from a larger
> pack of batteries, same voltage.

Think about what happens if you connect two buckets of water with a
siphon hose. Water flows from the higher one to the lower one, until
they are both at the same level. No pump is needed! If the water level
is quite a bit different, the initial rate of flow is quite high. But as
they near the same level, the amount of water that transfers gets lower
and lower. Depending on how big and how long your siphon hose is, it can
take a very long time for them to finally reach the same level.

Lead-acid batteries behave the same way when connected directly in
parallel. If both batteries are the same nominal voltage, current flows
from the more-charged one to the less-charged one, until they are both
at the same voltage and same state of charge. For instance, connect two
same-capacity batteries in parallel. One is fully charged, and one is
dead. They both end up at 50% state of charge.

If you connect them with big thick low-resistance wires, the initial
current can be very large! The peak is roughly the amphour capacity of
the biggest battery (i.e. 100 amps if it's a 100ah battery).

But it quickly falls to a low level, as the current makes the
higher-voltage battery drop, and the lower-voltage battery rises. It
takes a day or more for them to fully equalize to the same state of charge.

You can limit the current with resistance in the wires. Deliberately
using smaller or longer wires, for example. The voltage difference
between the batteries is quite small, so it doesn't take much resistance.

If you're in a hurry, then your "source" pack can be a little higher
voltage (no more than 10% higher than the "destination" pack). The
current flow will be even larger, and stay higher longer. You have to
monitor the current and time it carefully, so the lower-voltage pack
won't get overcharged. This is called "dump charging". Done right, it's
about the fastest way to charge batteries. Done wrong, it's one of the
best ways to destroy batteries!

Charging this way is very efficient. The only losses are the inevitable
efficiency losses in the batteries themselves. The wire between them is
essentially lossless.

> My questions for the list:  how do I transfer the charge from the solar
> bank to the EV pack?  Can I just use a charge cable directly and the two
> banks will equalize?

Yes. If they are the same nominal voltage, this is safe. You can leave
the cable connected as long as you like. Just be aware that the peak
current when first connected can be very high.

> Or would I need to use a charge controller?

You can. In fact, *some* kind of charge control is necessary when the
charging source is more than 10% above the battery's voltage.

The charge controller will inevitably lower your efficiency a bit.

> a 45 amp solar controller I could hook from the main battery pack to
> the EV pack but I fear the input amps would exceed it?

If this is a charge controller designed for PV cells to a battery, don't
use it with a battery (or other low-resistance) power source on its
input. It's intended to be powered by PV panels, which are a *current*
source. They can be safely shorted to reduce output. But you can't short
a battery or power supply!

--
If you're not stubborn, you'll give up on experiments too soon.
And if you're not flexible, you'll pound your head against the wall
and you won't see a different solution to a problem you're trying
to solve. -- Jeff Bezos
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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Re: Charging Batteries from Batteries?

Lee Hart
In reply to this post by EV professor
Dennis Miles wrote:
> When utilizing DUMP Charging, the particular cell chemistry makes a
> difference, the PbSO4 Lead acid can be charged with a heavy current but,
> lithium can not.

Agreed. What I wrote applies to lead-acid batteries. You can connect
other chemistry batteries in parallel, but they are not as safe or
foolproof as lead-acid.

Nicads can be discharged in parallel, but won't charge properly in
parallel. Their voltage reaches a peak just before fully charged, and
then *drops* as you finish charging. The first cell that peaks brings
the voltage down so the cell in parallel with it won't fully charge.

Nimh have a similar problem, though not as severe. There is also a
problem if the two cells are not at the same temperature. You can get a
"thermal runaway" situation where a hot cell's voltage falls, so it
draws current from the colder cell in parallel. This makes the hot cell
even hotter, so it pulls even more current etc. until both cells are dead.

There are so many different lithium chemistries that it's hard to say
what will happen. Small cells are routinely paralleled in laptops, which
has resulted in some spectacular fires when things go wrong. But it's
not clear what exactly is safe, and what is not safe. There is a great
deal of hearsay and ignorance-is-bliss.

> If you are charging from a much higher voltage pack you must limit
> the charging current, an ideal unit to do this is a DC motor controller.

No! A motor controller *depends* on the motor to provide an inductive
load. The motor's inductance is an essential part of the circuit. If you
want to use a motor controller as a battery charger, you *must* include
a sizable inductor in series with its output. Without it, a motor
controller can't limit current or regulate its output voltage.

--
If you're not stubborn, you'll give up on experiments too soon.
And if you're not flexible, you'll pound your head against the wall
and you won't see a different solution to a problem you're trying
to solve. -- Jeff Bezos
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
_______________________________________________
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Re: Charging Batteries from Batteries?

Roland Wiench
In reply to this post by Dan Baker
You also have to be careful not connect standard battery jumper cables.  This will cause a arc and could blow up your batteries if there is any hydrogen gas and or poor connection.

I use a battery load bank which I built for battery load testing and can also be used as a resistance to prevent the current surge.

The components consist of a steel equipment box, a 1/2 inch thick insulator board I pick up from a motor shop.  Two box lug terminal strips rated for 500 amp that is mounted on the insulator board.  A 500 DC contactor rated for the battery voltage with a coil rated at 12 vdc.  A momentary switch to control the contactor coil which is normally use for a single battery testing.  

A maintain switch for a longer on time of the contactor.  A volt and amp meter rated for the battery you are using.

The resistance is made from a high temperature stainless steel welding wires which is about 1/8 inch or 0.125 inch in diameter and 36 inches long.  They are loop back and forth with the ends connected to the two terminal strips place about 10 inches apart.  You can add more wires in series to limit your ampere.  I limit my ampere to about 200 amps using 10 wires in series for a battery pack rated at 180 volts at 250 ah. The welding wires are rated for over 1000 degrees F.

I used one wire to load test a 6 volt battery and two wires in series for a 12 volt battery for a 200 amp load.  

Drill a series of 1/2 inch vent holes on the top of the box and on the back of the box for ventilation.    

Used two brass motor terminals which is normally used on DC motors that I got from the motor shop.  I only connected the positive voltage through this load bank and the negative voltage connects directly from battery to battery.

You can also use a Power Anderson 300 to 400 amp receptacle on the vehicle to connect this device which is more safe.

Roland  
  ----- Original Message -----
  From: Lee Hart<mailto:[hidden email]>
  To: Electric Vehicle Discussion List<mailto:[hidden email]>
  Sent: Sunday, April 20, 2014 11:37 AM
  Subject: Re: [EVDL] Charging Batteries from Batteries?


  Dan Baker wrote:
  > I have question around charging the battery pack on an EV from a larger
  > pack of batteries, same voltage.

  Think about what happens if you connect two buckets of water with a
  siphon hose. Water flows from the higher one to the lower one, until
  they are both at the same level. No pump is needed! If the water level
  is quite a bit different, the initial rate of flow is quite high. But as
  they near the same level, the amount of water that transfers gets lower
  and lower. Depending on how big and how long your siphon hose is, it can
  take a very long time for them to finally reach the same level.

  Lead-acid batteries behave the same way when connected directly in
  parallel. If both batteries are the same nominal voltage, current flows
  from the more-charged one to the less-charged one, until they are both
  at the same voltage and same state of charge. For instance, connect two
  same-capacity batteries in parallel. One is fully charged, and one is
  dead. They both end up at 50% state of charge.

  If you connect them with big thick low-resistance wires, the initial
  current can be very large! The peak is roughly the amphour capacity of
  the biggest battery (i.e. 100 amps if it's a 100ah battery).

  But it quickly falls to a low level, as the current makes the
  higher-voltage battery drop, and the lower-voltage battery rises. It
  takes a day or more for them to fully equalize to the same state of charge.

  You can limit the current with resistance in the wires. Deliberately
  using smaller or longer wires, for example. The voltage difference
  between the batteries is quite small, so it doesn't take much resistance.

  If you're in a hurry, then your "source" pack can be a little higher
  voltage (no more than 10% higher than the "destination" pack). The
  current flow will be even larger, and stay higher longer. You have to
  monitor the current and time it carefully, so the lower-voltage pack
  won't get overcharged. This is called "dump charging". Done right, it's
  about the fastest way to charge batteries. Done wrong, it's one of the
  best ways to destroy batteries!

  Charging this way is very efficient. The only losses are the inevitable
  efficiency losses in the batteries themselves. The wire between them is
  essentially lossless.

  > My questions for the list:  how do I transfer the charge from the solar
  > bank to the EV pack?  Can I just use a charge cable directly and the two
  > banks will equalize?

  Yes. If they are the same nominal voltage, this is safe. You can leave
  the cable connected as long as you like. Just be aware that the peak
  current when first connected can be very high.

  > Or would I need to use a charge controller?

  You can. In fact, *some* kind of charge control is necessary when the
  charging source is more than 10% above the battery's voltage.

  The charge controller will inevitably lower your efficiency a bit.

  > a 45 amp solar controller I could hook from the main battery pack to
  > the EV pack but I fear the input amps would exceed it?

  If this is a charge controller designed for PV cells to a battery, don't
  use it with a battery (or other low-resistance) power source on its
  input. It's intended to be powered by PV panels, which are a *current*
  source. They can be safely shorted to reduce output. But you can't short
  a battery or power supply!

  --
  If you're not stubborn, you'll give up on experiments too soon.
  And if you're not flexible, you'll pound your head against the wall
  and you won't see a different solution to a problem you're trying
  to solve. -- Jeff Bezos
  --
  Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm<http://www.sunrise-ev.com/LeesEVs.htm>
  _______________________________________________
  UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<http://www.evdl.org/help/index.html#usub>
  http://lists.evdl.org/listinfo.cgi/ev-evdl.org<http://lists.evdl.org/listinfo.cgi/ev-evdl.org>
  For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA<http://groups.yahoo.com/group/NEDRA>)

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Re: Charging your EV pack from other batteries?

Cor van de Water
In reply to this post by Dan Baker
Dan,
The speed of charging will indeed be very dependent on the
difference between the state of charge of the two packs
and if you want to transfer more energy than half the
capacity that is in the solar bank, you will not be able
to do that by simply wiring them together, as the packs
will tend to go to the same state of charge and also it will
take a long time once the charge levels start to get close
to each other.
It is simple to improve this and no big converters are needed,
since all you need to do is to increase the input voltage
a little bit.
For example, I have these "half-brick" (about 3x3") DC/DC converter
modules that take as input 48V nominal (36-75V allowed) and deliver
5V 30A.
Just one such a module wired to the solar battery can be added in
series with the solar bank voltage to boost it from 48 to 53V
which will allow the boat's pack to charge quickly (up to 30A
when using 1 module, up to 60A when using 2 of them in parallel)

This means that your boat can be charged to 80% in about 3 hours
(or 1.5 hours if you use 2 modules) even if the solar bank voltage
is lower than the boat's pack charging voltage, due to the boost.
The efficiency is still around 90% since you boost the power up
by about 10% (5V on a 50V pack) and consequently the output current
is 90% of the input current (the DC/DC converter consumes about
10% of the charging current to provide the 5V boost).

Hope this clarifies and gives some ideas.
Let me know if you are interested in getting a module.

Note that I have two versions of this same 150W module:
one has 5V output, the other 15V output and both can be
trimmed up/down, so you can use such a module also so provide
12V for lights and accessories powered from a 48V pack.

Success,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     XoIP: +31877841130
Tel: +1 408 383 7626        Tel: +91 (040)23117400 x203



-----Original Message-----
From: [hidden email] on behalf of Dan Baker
Sent: Sun 4/20/2014 6:13 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Charging your EV pack from other batteries?
 
Thank you Bruce, Dennis, Willie and Marco for the info.  So it sounds like
a charge from batteries of similar voltage could work, although the charge
wouldn't be very robust/complete depending on the difference in state of
charge between the packs?  I expect the best charge would be if the solar
pack is fully charged and the PV array is under full sunlight conditions
and the least would be at night and both packs have been partially drained?
 Like most leisure craft my boats spend most of the time parked at dock so
I would expect the EV pack would likely be connected under the PV pack
being charged most of the time.  Dump charging or high speed charging
really isn't necessary for my use but a quicker than the normal 6-10 hour
charge would be nice.  I guess I could also use an invertor to convert the
48 volts to 120 volts and plug in my regular wall charger to have a
complete charge (cheaply make a high amp step up circuit like Marco
suggested) but that sounds much more terribly inefficient. :-(

Cheers
Dan


On Sat, Apr 19, 2014 at 10:41 PM, Bruce EVangel Parmenter <
[hidden email]> wrote:

> I have seen drivers charge their pack from another pack.
>
> The first instance was when I heard of a couple in the East SF Bay EAA
> Chapter, the Cornell's, who both drove EVs. Talk about getting the most
> out of the $ they spent on a pack, when a pack was replaced because its
> range did not suit their needs, the batteries that still had life in
> them were stored in the garage, and kept charged from the solar array on
> their roof (this was at a time when there were no solar incentives, and
> the Cornell's were way ahead of everyone else. Their roof solar would be
> thought of as common place by today's standards).
>
> When one of them got home, they would recharge their EV off the older
> pack which had been recharged from solar electrons. The current they
> used to recharge their pack was low, so I would not call it a dump
> charge. At that time, a dump charge was what the racers were doing at
> the track with high currents (like level-3 power), to get back out to
> race on the track (APS racing).
>
> The other experience was at high current levels, so you could call it a
> dump charge of sorts. In both cases, the effort to transfer the power
> from one pack to the other was a manual one, where the human brain was
> the smart charger. They each used a source pack that was at an
> incrementally higher voltage (higher than a destination pack voltage).
>
> The example is when I hung out with John Wayland at a Sacramento Raceway
> nedra.com EVent. His White Zombie at the time I believe had the smaller
> Jonson Controls agms. His older pack that used to be in his EV were made
> up of Optima yellow top agms. When he came in to his pit location after
> doing his run, he would measure his pack voltage, and match that plus
> one more 12V agm. Then connect the slightly higher voltage old pack to
> his EV's partially spent pack. As the dump current decreased, he would
> add another 12 agm to bump up the current. He knew from experience when
> to do this so as to not push too much dump current, and to not waste
> time on a lower, slower dump current.
>
> When John's EV pack had reached the finishing voltage, he pushed/goosed
> it a little, forcing a higher than normal finishing current into his
> EV's pack. This caused his EV's agm pack to steam some of the
> electrolyte. John said he did this on purpose because his hot pack
> performed better (one could like that thinking: prematurely
> aging/destroying his EV's agm pack just so he can get a better race
> time, to what the ice heads to when they push their ice beyond
> red-line).  After he left to go get in line to race again, he had a
> genset pushing power into the old Optima set of batteries that was in
> his support vehicle.
>
> I've heard of drivers of today using a controller to push the power from
> one pack to another. IT still would require a human to incrementally
> bump the current up as the pack charged, but no batteries had to be
> added, you could start out by using the highest source pack voltage.
>
>
> {brucedp.150m.com}
>
>
>
> -
> On Sat, Apr 19, 2014, at 02:12 PM, Dan Baker wrote:
> > Hello fellow Evlist users,
> > I have question around charging the battery pack on an EV from a larger
> > pack of batteries, same voltage. I'm looking to build a stationary solar
> > array (48v) and charging 12 x 12 volt 133 amp/hr sealed lead acid
> > batteries, 4 batteries per bank  These are retired but gently used UPS
> > batteries and I will have about 1200 watts in solar going into a
> > Morningstar 45 amp solar controller.  I would like to be able to charge
> > my
> > EV boat pack (http://www.evalbum.com/4767) from this pack, UPS batteries
> > again, but 4 x 12 volt AGM 133 amp/hr.
> > My questions for the list:  how do I transfer the charge from the solar
> > bank to the EV pack?  Can I just use a charge cable directly and the two
> > banks will equalize?  Or would I need to use a charge controller?   I
> > have
> > another 45 amp solar controller I could hook from the main battery pack
> > to
> > the EV pack but I fear the input amps would exceed it?  I remember a
> > while
> > back someone mentioned they were charging a lawnmower from a truck pack,
> > wish I could find more info on this ...
> -
>
> --
> http://www.fastmail.fm - Or how I learned to stop worrying and
>                           love email again
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: Charging your EV pack from other batteries?

Marco Gaxiola
Cor,

        That is a great and very easy idea!

Dan,

        Up to I understood Cor's email; I drew this schematic:
https://plus.google.com/109469848356360136281/posts/XzZ8vE83Bb2  to confirm
that. You just must assure that the DC-DC converter be an 'isolated'
version.  (most of them are)  



Ing. Marco Gaxiola
EvMarch - Director
https://www.facebook.com/EvMarch 



-----Mensaje original-----
De: [hidden email] [mailto:[hidden email]] En nombre
de Cor van de Water
Enviado el: domingo, 20 de abril de 2014 07:11 p.m.
Para: Electric Vehicle Discussion List
Asunto: Re: [EVDL] Charging your EV pack from other batteries?

Dan,
The speed of charging will indeed be very dependent on the difference
between the state of charge of the two packs and if you want to transfer
more energy than half the capacity that is in the solar bank, you will not
be able to do that by simply wiring them together, as the packs will tend to
go to the same state of charge and also it will take a long time once the
charge levels start to get close to each other.
It is simple to improve this and no big converters are needed, since all you
need to do is to increase the input voltage a little bit.
For example, I have these "half-brick" (about 3x3") DC/DC converter modules
that take as input 48V nominal (36-75V allowed) and deliver 5V 30A.
Just one such a module wired to the solar battery can be added in series
with the solar bank voltage to boost it from 48 to 53V which will allow the
boat's pack to charge quickly (up to 30A when using 1 module, up to 60A when
using 2 of them in parallel)

This means that your boat can be charged to 80% in about 3 hours (or 1.5
hours if you use 2 modules) even if the solar bank voltage is lower than the
boat's pack charging voltage, due to the boost.
The efficiency is still around 90% since you boost the power up by about 10%
(5V on a 50V pack) and consequently the output current is 90% of the input
current (the DC/DC converter consumes about 10% of the charging current to
provide the 5V boost).

Hope this clarifies and gives some ideas.
Let me know if you are interested in getting a module.

Note that I have two versions of this same 150W module:
one has 5V output, the other 15V output and both can be trimmed up/down, so
you can use such a module also so provide 12V for lights and accessories
powered from a 48V pack.

Success,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     XoIP: +31877841130
Tel: +1 408 383 7626        Tel: +91 (040)23117400 x203



-----Original Message-----
From: [hidden email] on behalf of Dan Baker
Sent: Sun 4/20/2014 6:13 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Charging your EV pack from other batteries?
 
Thank you Bruce, Dennis, Willie and Marco for the info.  So it sounds like a
charge from batteries of similar voltage could work, although the charge
wouldn't be very robust/complete depending on the difference in state of
charge between the packs?  I expect the best charge would be if the solar
pack is fully charged and the PV array is under full sunlight conditions and
the least would be at night and both packs have been partially drained?
 Like most leisure craft my boats spend most of the time parked at dock so I
would expect the EV pack would likely be connected under the PV pack being
charged most of the time.  Dump charging or high speed charging really isn't
necessary for my use but a quicker than the normal 6-10 hour charge would be
nice.  I guess I could also use an invertor to convert the
48 volts to 120 volts and plug in my regular wall charger to have a complete
charge (cheaply make a high amp step up circuit like Marco
suggested) but that sounds much more terribly inefficient. :-(

Cheers
Dan


On Sat, Apr 19, 2014 at 10:41 PM, Bruce EVangel Parmenter <
[hidden email]> wrote:

> I have seen drivers charge their pack from another pack.
>
> The first instance was when I heard of a couple in the East SF Bay EAA
> Chapter, the Cornell's, who both drove EVs. Talk about getting the
> most out of the $ they spent on a pack, when a pack was replaced
> because its range did not suit their needs, the batteries that still
> had life in them were stored in the garage, and kept charged from the
> solar array on their roof (this was at a time when there were no solar
> incentives, and the Cornell's were way ahead of everyone else. Their
> roof solar would be thought of as common place by today's standards).
>
> When one of them got home, they would recharge their EV off the older
> pack which had been recharged from solar electrons. The current they
> used to recharge their pack was low, so I would not call it a dump
> charge. At that time, a dump charge was what the racers were doing at
> the track with high currents (like level-3 power), to get back out to
> race on the track (APS racing).
>
> The other experience was at high current levels, so you could call it
> a dump charge of sorts. In both cases, the effort to transfer the
> power from one pack to the other was a manual one, where the human
> brain was the smart charger. They each used a source pack that was at
> an incrementally higher voltage (higher than a destination pack voltage).
>
> The example is when I hung out with John Wayland at a Sacramento
> Raceway nedra.com EVent. His White Zombie at the time I believe had
> the smaller Jonson Controls agms. His older pack that used to be in
> his EV were made up of Optima yellow top agms. When he came in to his
> pit location after doing his run, he would measure his pack voltage,
> and match that plus one more 12V agm. Then connect the slightly higher
> voltage old pack to his EV's partially spent pack. As the dump current
> decreased, he would add another 12 agm to bump up the current. He knew
> from experience when to do this so as to not push too much dump
> current, and to not waste time on a lower, slower dump current.
>
> When John's EV pack had reached the finishing voltage, he
> pushed/goosed it a little, forcing a higher than normal finishing
> current into his EV's pack. This caused his EV's agm pack to steam
> some of the electrolyte. John said he did this on purpose because his
> hot pack performed better (one could like that thinking: prematurely
> aging/destroying his EV's agm pack just so he can get a better race
> time, to what the ice heads to when they push their ice beyond
> red-line).  After he left to go get in line to race again, he had a
> genset pushing power into the old Optima set of batteries that was in
> his support vehicle.
>
> I've heard of drivers of today using a controller to push the power
> from one pack to another. IT still would require a human to
> incrementally bump the current up as the pack charged, but no
> batteries had to be added, you could start out by using the highest source
pack voltage.

>
>
> {brucedp.150m.com}
>
>
>
> -
> On Sat, Apr 19, 2014, at 02:12 PM, Dan Baker wrote:
> > Hello fellow Evlist users,
> > I have question around charging the battery pack on an EV from a
> > larger pack of batteries, same voltage. I'm looking to build a
> > stationary solar array (48v) and charging 12 x 12 volt 133 amp/hr
> > sealed lead acid batteries, 4 batteries per bank  These are retired
> > but gently used UPS batteries and I will have about 1200 watts in
> > solar going into a Morningstar 45 amp solar controller.  I would
> > like to be able to charge my EV boat pack
> > (http://www.evalbum.com/4767) from this pack, UPS batteries again,
> > but 4 x 12 volt AGM 133 amp/hr.
> > My questions for the list:  how do I transfer the charge from the
> > solar bank to the EV pack?  Can I just use a charge cable directly and
the two

> > banks will equalize?  Or would I need to use a charge controller?   I
> > have
> > another 45 amp solar controller I could hook from the main battery
> > pack to the EV pack but I fear the input amps would exceed it?  I
> > remember a while back someone mentioned they were charging a
> > lawnmower from a truck pack, wish I could find more info on this ...
> -
>
> --
> http://www.fastmail.fm - Or how I learned to stop worrying and
>                           love email again
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: Charging your EV pack from other batteries?

Cor van de Water
Hi Marco,
Yep, you got it!
And indeed - these converters are isolated, so they will be
able to do this, as well as the other task of delivering an
isolated 13-14V for lights and accessories off of a 48V pack.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     XoIP: +31877841130
Tel: +1 408 383 7626        Tel: +91 (040)23117400 x203



-----Original Message-----
From: [hidden email] on behalf of Ing. Marco Gaxiola
Sent: Sun 4/20/2014 9:31 PM
To: 'Electric Vehicle Discussion List'
Subject: Re: [EVDL] Charging your EV pack from other batteries?
 
Cor,

        That is a great and very easy idea!

Dan,

        Up to I understood Cor's email; I drew this schematic:
https://plus.google.com/109469848356360136281/posts/XzZ8vE83Bb2  to confirm
that. You just must assure that the DC-DC converter be an 'isolated'
version.  (most of them are)  



Ing. Marco Gaxiola
EvMarch - Director
https://www.facebook.com/EvMarch 



-----Mensaje original-----
De: [hidden email] [mailto:[hidden email]] En nombre
de Cor van de Water
Enviado el: domingo, 20 de abril de 2014 07:11 p.m.
Para: Electric Vehicle Discussion List
Asunto: Re: [EVDL] Charging your EV pack from other batteries?

Dan,
The speed of charging will indeed be very dependent on the difference
between the state of charge of the two packs and if you want to transfer
more energy than half the capacity that is in the solar bank, you will not
be able to do that by simply wiring them together, as the packs will tend to
go to the same state of charge and also it will take a long time once the
charge levels start to get close to each other.
It is simple to improve this and no big converters are needed, since all you
need to do is to increase the input voltage a little bit.
For example, I have these "half-brick" (about 3x3") DC/DC converter modules
that take as input 48V nominal (36-75V allowed) and deliver 5V 30A.
Just one such a module wired to the solar battery can be added in series
with the solar bank voltage to boost it from 48 to 53V which will allow the
boat's pack to charge quickly (up to 30A when using 1 module, up to 60A when
using 2 of them in parallel)

This means that your boat can be charged to 80% in about 3 hours (or 1.5
hours if you use 2 modules) even if the solar bank voltage is lower than the
boat's pack charging voltage, due to the boost.
The efficiency is still around 90% since you boost the power up by about 10%
(5V on a 50V pack) and consequently the output current is 90% of the input
current (the DC/DC converter consumes about 10% of the charging current to
provide the 5V boost).

Hope this clarifies and gives some ideas.
Let me know if you are interested in getting a module.

Note that I have two versions of this same 150W module:
one has 5V output, the other 15V output and both can be trimmed up/down, so
you can use such a module also so provide 12V for lights and accessories
powered from a 48V pack.

Success,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     XoIP: +31877841130
Tel: +1 408 383 7626        Tel: +91 (040)23117400 x203



-----Original Message-----
From: [hidden email] on behalf of Dan Baker
Sent: Sun 4/20/2014 6:13 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Charging your EV pack from other batteries?
 
Thank you Bruce, Dennis, Willie and Marco for the info.  So it sounds like a
charge from batteries of similar voltage could work, although the charge
wouldn't be very robust/complete depending on the difference in state of
charge between the packs?  I expect the best charge would be if the solar
pack is fully charged and the PV array is under full sunlight conditions and
the least would be at night and both packs have been partially drained?
 Like most leisure craft my boats spend most of the time parked at dock so I
would expect the EV pack would likely be connected under the PV pack being
charged most of the time.  Dump charging or high speed charging really isn't
necessary for my use but a quicker than the normal 6-10 hour charge would be
nice.  I guess I could also use an invertor to convert the
48 volts to 120 volts and plug in my regular wall charger to have a complete
charge (cheaply make a high amp step up circuit like Marco
suggested) but that sounds much more terribly inefficient. :-(

Cheers
Dan


On Sat, Apr 19, 2014 at 10:41 PM, Bruce EVangel Parmenter <
[hidden email]> wrote:

> I have seen drivers charge their pack from another pack.
>
> The first instance was when I heard of a couple in the East SF Bay EAA
> Chapter, the Cornell's, who both drove EVs. Talk about getting the
> most out of the $ they spent on a pack, when a pack was replaced
> because its range did not suit their needs, the batteries that still
> had life in them were stored in the garage, and kept charged from the
> solar array on their roof (this was at a time when there were no solar
> incentives, and the Cornell's were way ahead of everyone else. Their
> roof solar would be thought of as common place by today's standards).
>
> When one of them got home, they would recharge their EV off the older
> pack which had been recharged from solar electrons. The current they
> used to recharge their pack was low, so I would not call it a dump
> charge. At that time, a dump charge was what the racers were doing at
> the track with high currents (like level-3 power), to get back out to
> race on the track (APS racing).
>
> The other experience was at high current levels, so you could call it
> a dump charge of sorts. In both cases, the effort to transfer the
> power from one pack to the other was a manual one, where the human
> brain was the smart charger. They each used a source pack that was at
> an incrementally higher voltage (higher than a destination pack voltage).
>
> The example is when I hung out with John Wayland at a Sacramento
> Raceway nedra.com EVent. His White Zombie at the time I believe had
> the smaller Jonson Controls agms. His older pack that used to be in
> his EV were made up of Optima yellow top agms. When he came in to his
> pit location after doing his run, he would measure his pack voltage,
> and match that plus one more 12V agm. Then connect the slightly higher
> voltage old pack to his EV's partially spent pack. As the dump current
> decreased, he would add another 12 agm to bump up the current. He knew
> from experience when to do this so as to not push too much dump
> current, and to not waste time on a lower, slower dump current.
>
> When John's EV pack had reached the finishing voltage, he
> pushed/goosed it a little, forcing a higher than normal finishing
> current into his EV's pack. This caused his EV's agm pack to steam
> some of the electrolyte. John said he did this on purpose because his
> hot pack performed better (one could like that thinking: prematurely
> aging/destroying his EV's agm pack just so he can get a better race
> time, to what the ice heads to when they push their ice beyond
> red-line).  After he left to go get in line to race again, he had a
> genset pushing power into the old Optima set of batteries that was in
> his support vehicle.
>
> I've heard of drivers of today using a controller to push the power
> from one pack to another. IT still would require a human to
> incrementally bump the current up as the pack charged, but no
> batteries had to be added, you could start out by using the highest source
pack voltage.

>
>
> {brucedp.150m.com}
>
>
>
> -
> On Sat, Apr 19, 2014, at 02:12 PM, Dan Baker wrote:
> > Hello fellow Evlist users,
> > I have question around charging the battery pack on an EV from a
> > larger pack of batteries, same voltage. I'm looking to build a
> > stationary solar array (48v) and charging 12 x 12 volt 133 amp/hr
> > sealed lead acid batteries, 4 batteries per bank  These are retired
> > but gently used UPS batteries and I will have about 1200 watts in
> > solar going into a Morningstar 45 amp solar controller.  I would
> > like to be able to charge my EV boat pack
> > (http://www.evalbum.com/4767) from this pack, UPS batteries again,
> > but 4 x 12 volt AGM 133 amp/hr.
> > My questions for the list:  how do I transfer the charge from the
> > solar bank to the EV pack?  Can I just use a charge cable directly and
the two

> > banks will equalize?  Or would I need to use a charge controller?   I
> > have
> > another 45 amp solar controller I could hook from the main battery
> > pack to the EV pack but I fear the input amps would exceed it?  I
> > remember a while back someone mentioned they were charging a
> > lawnmower from a truck pack, wish I could find more info on this ...
> -
>
> --
> http://www.fastmail.fm - Or how I learned to stop worrying and
>                           love email again
>
> _______________________________________________
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> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: Charging Batteries from Batteries?

Martin WINLOW
In reply to this post by Roland Wiench
Hi Roland,

I do love your wonderfully practical take on things - when are you going to write a book?

Anyway, from my rudimentary understanding of these things, 180V / 200A = 0.9 ohms of resistance in your welding rods.  200A x 200A x 0.9 ohms = 36kW of heat from your resistor.  That sounds horribly wasteful if you are doing it for any significant amount of time... Care to comment on that?


On 20 Apr 2014, at 19:39, Roland wrote:

> You also have to be careful not connect standard battery jumper cables.  This will cause a arc and could blow up your batteries if there is any hydrogen gas and or poor connection.
>
> I use a battery load bank which I built for battery load testing and can also be used as a resistance to prevent the current surge.
>
> The components consist of a steel equipment box, a 1/2 inch thick insulator board I pick up from a motor shop.  Two box lug terminal strips rated for 500 amp that is mounted on the insulator board.  A 500 DC contactor rated for the battery voltage with a coil rated at 12 vdc.  A momentary switch to control the contactor coil which is normally use for a single battery testing.  
>
> A maintain switch for a longer on time of the contactor.  A volt and amp meter rated for the battery you are using.
>
> The resistance is made from a high temperature stainless steel welding wires which is about 1/8 inch or 0.125 inch in diameter and 36 inches long.  They are loop back and forth with the ends connected to the two terminal strips place about 10 inches apart.  You can add more wires in series to limit your ampere.  I limit my ampere to about 200 amps using 10 wires in series for a battery pack rated at 180 volts at 250 ah. The welding wires are rated for over 1000 degrees F.
>
> I used one wire to load test a 6 volt battery and two wires in series for a 12 volt battery for a 200 amp load.  
>
> Drill a series of 1/2 inch vent holes on the top of the box and on the back of the box for ventilation.    
>
> Used two brass motor terminals which is normally used on DC motors that I got from the motor shop.  I only connected the positive voltage through this load bank and the negative voltage connects directly from battery to battery.
>
> You can also use a Power Anderson 300 to 400 amp receptacle on the vehicle to connect this device which is more safe.
>
> Roland  
>  ----- Original Message -----
>  From: Lee Hart<mailto:[hidden email]>
>  To: Electric Vehicle Discussion List<mailto:[hidden email]>
>  Sent: Sunday, April 20, 2014 11:37 AM
>  Subject: Re: [EVDL] Charging Batteries from Batteries?
>
>
>  Dan Baker wrote:
>> I have question around charging the battery pack on an EV from a larger
>> pack of batteries, same voltage.
>
>  Think about what happens if you connect two buckets of water with a
>  siphon hose. Water flows from the higher one to the lower one, until
>  they are both at the same level. No pump is needed! If the water level
>  is quite a bit different, the initial rate of flow is quite high. But as
>  they near the same level, the amount of water that transfers gets lower
>  and lower. Depending on how big and how long your siphon hose is, it can
>  take a very long time for them to finally reach the same level.
>
>  Lead-acid batteries behave the same way when connected directly in
>  parallel. If both batteries are the same nominal voltage, current flows
>  from the more-charged one to the less-charged one, until they are both
>  at the same voltage and same state of charge. For instance, connect two
>  same-capacity batteries in parallel. One is fully charged, and one is
>  dead. They both end up at 50% state of charge.
>
>  If you connect them with big thick low-resistance wires, the initial
>  current can be very large! The peak is roughly the amphour capacity of
>  the biggest battery (i.e. 100 amps if it's a 100ah battery).
>
>  But it quickly falls to a low level, as the current makes the
>  higher-voltage battery drop, and the lower-voltage battery rises. It
>  takes a day or more for them to fully equalize to the same state of charge.
>
>  You can limit the current with resistance in the wires. Deliberately
>  using smaller or longer wires, for example. The voltage difference
>  between the batteries is quite small, so it doesn't take much resistance.
>
>  If you're in a hurry, then your "source" pack can be a little higher
>  voltage (no more than 10% higher than the "destination" pack). The
>  current flow will be even larger, and stay higher longer. You have to
>  monitor the current and time it carefully, so the lower-voltage pack
>  won't get overcharged. This is called "dump charging". Done right, it's
>  about the fastest way to charge batteries. Done wrong, it's one of the
>  best ways to destroy batteries!
>
>  Charging this way is very efficient. The only losses are the inevitable
>  efficiency losses in the batteries themselves. The wire between them is
>  essentially lossless.
>
>> My questions for the list:  how do I transfer the charge from the solar
>> bank to the EV pack?  Can I just use a charge cable directly and the two
>> banks will equalize?
>
>  Yes. If they are the same nominal voltage, this is safe. You can leave
>  the cable connected as long as you like. Just be aware that the peak
>  current when first connected can be very high.
>
>> Or would I need to use a charge controller?
>
>  You can. In fact, *some* kind of charge control is necessary when the
>  charging source is more than 10% above the battery's voltage.
>
>  The charge controller will inevitably lower your efficiency a bit.
>
>> a 45 amp solar controller I could hook from the main battery pack to
>> the EV pack but I fear the input amps would exceed it?
>
>  If this is a charge controller designed for PV cells to a battery, don't
>  use it with a battery (or other low-resistance) power source on its
>  input. It's intended to be powered by PV panels, which are a *current*
>  source. They can be safely shorted to reduce output. But you can't short
>  a battery or power supply!
>
>  --
>  If you're not stubborn, you'll give up on experiments too soon.
>  And if you're not flexible, you'll pound your head against the wall
>  and you won't see a different solution to a problem you're trying
>  to solve. -- Jeff Bezos
>  --
>  Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm<http://www.sunrise-ev.com/LeesEVs.htm>
>  _______________________________________________
>  UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<http://www.evdl.org/help/index.html#usub>
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Re: Charging Batteries from Batteries?

EV professor
Martin, the way Roland is using the load bank is as a 0.9 ohm series
resistor for current limiting. the applied voltage in that case is only the
difference between  the Charged one and the one being charged, not 180 V.
but perhaps 20 or 40 volts limiting current to 22 to 44 amperes. If he was
trying to ascertain the battery condition he would connect it to a battery
and the measure the amount of discharge voltage reduction under load to
"Test" the battery in a short time at 200 ampere discharge rate.

*Dennis Lee Miles *






On Mon, Apr 21, 2014 at 3:44 AM, Martin WINLOW <[hidden email]> wrote:

> Hi Roland,
>
> I do love your wonderfully practical take on things - when are you going
> to write a book?
>
> Anyway, from my rudimentary understanding of these things, 180V / 200A =
> 0.9 ohms of resistance in your welding rods.  200A x 200A x 0.9 ohms = 36kW
> of heat from your resistor.  That sounds horribly wasteful if you are doing
> it for any significant amount of time... Care to comment on that?
>
>
> On 20 Apr 2014, at 19:39, Roland wrote:
>
> > You also have to be careful not connect standard battery jumper cables.
>  This will cause a arc and could blow up your batteries if there is any
> hydrogen gas and or poor connection.
> >
> > I use a battery load bank which I built for battery load testing and can
> also be used as a resistance to prevent the current surge.
> >
> > The components consist of a steel equipment box, a 1/2 inch thick
> insulator board I pick up from a motor shop.  Two box lug terminal strips
> rated for 500 amp that is mounted on the insulator board.  A 500 DC
> contactor rated for the battery voltage with a coil rated at 12 vdc.  A
> momentary switch to control the contactor coil which is normally use for a
> single battery testing.
> >
> > A maintain switch for a longer on time of the contactor.  A volt and amp
> meter rated for the battery you are using.
> >
> > The resistance is made from a high temperature stainless steel welding
> wires which is about 1/8 inch or 0.125 inch in diameter and 36 inches long.
>  They are loop back and forth with the ends connected to the two terminal
> strips place about 10 inches apart.  You can add more wires in series to
> limit your ampere.  I limit my ampere to about 200 amps using 10 wires in
> series for a battery pack rated at 180 volts at 250 ah. The welding wires
> are rated for over 1000 degrees F.
> >
> > I used one wire to load test a 6 volt battery and two wires in series
> for a 12 volt battery for a 200 amp load.
> >
> > Drill a series of 1/2 inch vent holes on the top of the box and on the
> back of the box for ventilation.
> >
> > Used two brass motor terminals which is normally used on DC motors that
> I got from the motor shop.  I only connected the positive voltage through
> this load bank and the negative voltage connects directly from battery to
> battery.
> >
> > You can also use a Power Anderson 300 to 400 amp receptacle on the
> vehicle to connect this device which is more safe.
> >
> > Roland
> >  ----- Original Message -----
> >  From: Lee Hart<mailto:[hidden email]>
> >  To: Electric Vehicle Discussion List<mailto:[hidden email]>
> >  Sent: Sunday, April 20, 2014 11:37 AM
> >  Subject: Re: [EVDL] Charging Batteries from Batteries?
> >
> >
> >  Dan Baker wrote:
> >> I have question around charging the battery pack on an EV from a larger
> >> pack of batteries, same voltage.
> >
> >  Think about what happens if you connect two buckets of water with a
> >  siphon hose. Water flows from the higher one to the lower one, until
> >  they are both at the same level. No pump is needed! If the water level
> >  is quite a bit different, the initial rate of flow is quite high. But as
> >  they near the same level, the amount of water that transfers gets lower
> >  and lower. Depending on how big and how long your siphon hose is, it can
> >  take a very long time for them to finally reach the same level.
> >
> >  Lead-acid batteries behave the same way when connected directly in
> >  parallel. If both batteries are the same nominal voltage, current flows
> >  from the more-charged one to the less-charged one, until they are both
> >  at the same voltage and same state of charge. For instance, connect two
> >  same-capacity batteries in parallel. One is fully charged, and one is
> >  dead. They both end up at 50% state of charge.
> >
> >  If you connect them with big thick low-resistance wires, the initial
> >  current can be very large! The peak is roughly the amphour capacity of
> >  the biggest battery (i.e. 100 amps if it's a 100ah battery).
> >
> >  But it quickly falls to a low level, as the current makes the
> >  higher-voltage battery drop, and the lower-voltage battery rises. It
> >  takes a day or more for them to fully equalize to the same state of
> charge.
> >
> >  You can limit the current with resistance in the wires. Deliberately
> >  using smaller or longer wires, for example. The voltage difference
> >  between the batteries is quite small, so it doesn't take much
> resistance.
> >
> >  If you're in a hurry, then your "source" pack can be a little higher
> >  voltage (no more than 10% higher than the "destination" pack). The
> >  current flow will be even larger, and stay higher longer. You have to
> >  monitor the current and time it carefully, so the lower-voltage pack
> >  won't get overcharged. This is called "dump charging". Done right, it's
> >  about the fastest way to charge batteries. Done wrong, it's one of the
> >  best ways to destroy batteries!
> >
> >  Charging this way is very efficient. The only losses are the inevitable
> >  efficiency losses in the batteries themselves. The wire between them is
> >  essentially lossless.
> >
> >> My questions for the list:  how do I transfer the charge from the solar
> >> bank to the EV pack?  Can I just use a charge cable directly and the two
> >> banks will equalize?
> >
> >  Yes. If they are the same nominal voltage, this is safe. You can leave
> >  the cable connected as long as you like. Just be aware that the peak
> >  current when first connected can be very high.
> >
> >> Or would I need to use a charge controller?
> >
> >  You can. In fact, *some* kind of charge control is necessary when the
> >  charging source is more than 10% above the battery's voltage.
> >
> >  The charge controller will inevitably lower your efficiency a bit.
> >
> >> a 45 amp solar controller I could hook from the main battery pack to
> >> the EV pack but I fear the input amps would exceed it?
> >
> >  If this is a charge controller designed for PV cells to a battery, don't
> >  use it with a battery (or other low-resistance) power source on its
> >  input. It's intended to be powered by PV panels, which are a *current*
> >  source. They can be safely shorted to reduce output. But you can't short
> >  a battery or power supply!
> >
> >  --
> >  If you're not stubborn, you'll give up on experiments too soon.
> >  And if you're not flexible, you'll pound your head against the wall
> >  and you won't see a different solution to a problem you're trying
> >  to solve. -- Jeff Bezos
> >  --
> >  Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm<
> http://www.sunrise-ev.com/LeesEVs.htm>
> >  _______________________________________________
> >  UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<
> http://www.evdl.org/help/index.html#usub>
> >  http://lists.evdl.org/listinfo.cgi/ev-evdl.org<
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org>
> >  For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA<http://groups.yahoo.com/group/NEDRA>)
> >
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Re: Charging your EV pack from other batteries?

EcoReality
In reply to this post by brucedp5
Electric Motor Werks actually says you can do this with their charger (http://emotorwerks.com/tech/electronics):

"Both non-PFC and PFC units can be used to charge your battery from a DC source. This feature can be used to charge one EV from another, to use the charger with a separate rectifier (e.g., for 3-phase operation), charger your EV from your solar array / stationary battery, etc. Non-PFC units can be used with DC input above the voltage of the battery being charged (up to ~400 VDC)
PFC units can be used with any DC source ~100-400VDC."

Anyone have experience with EMW chargers? I'm considering one, because my current (hah!) charging method is to charge five batteries at a time with a 40V/40A lab power supply. That means five days for a full charge of my 24 batteries. :-(

Jan

> Note that MANY switching power supplies can be run from DC. This means the best way to charge from another EV MAY be through your charger.
>
> If your charger has a "universal" AC input, such as "110 VAC to 240 VAC," then chances are that the first thing the line sees is a bridge rectifier, which changes AC into DC. The rectifier will "commutate" your DC in the proper direction, so you don't even need to worry about polarity. Most modern chargers are over 95% efficient.
>
> So, the BEST way to assure you get the proper charge for your batteries from another EV might be to connect your AC charger to the other EV's battery pack -- assuming it doesn't go over the peak voltage that the AC line would supply to it. (Generally, 240 * 1.414, or about 340 VDC.)
>
> You probably cannot do this with a charger that has a voltage selection switch that lets it operate on either 120 VAC or 240 VAC. That implies that there may be transformer or other AC-specific component in there. And the charging current available may be reduced by 50%, since only half the input bridge rectifier is being used.
>
> (If you think you may be doing this often, and have the proper skills and documentation, you might bypass the input bridge entirely to get back the full charging current capability.)
>
> Kids, don't try this at home! Unless you're skilled at electronics and have a schematic, the next step would be to contact your charger's manufacturer to see if they think this is a good idea! (And for liability reasons, they likely won't. See if you can talk to one of their engineers, not a sales droid. And see if you can wrangle schematics out of them.)
>
:::: Given an infinite source of energy, population growth still produces an inescapable problem. The problem of the acquisition of energy is replaced by the problem of its dissipation. -- Garrett Hardin
:::: Jan Steinman, EcoReality Co-op ::::

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Re: Charging your EV pack from other batteries?

Cor van de Water
Jan,
The OP requested charging his boat's 48V pack from his 48V solar bank,
so I doubt that the EMW charger or other standard 110-240V AC supplies/
chargers will work on 48V DC. For charging from a road-going EV as
input,
that may be possible though it is always a challenge to discover the
limitations of the setup before they cause failure and that can be in a
catastrophic way - think about an input stage that has 4 diodes that
rectify the AC input, but now all current only goes through 2 diodes
so they may overheat and fail, which is designed to be handled by the
fuse blowing up, but the fuse is only designed to work on AC, so it
creates an conductive arc instead and the current continues to flow....
Usually things don't fail this badly but you need to be aware of what
can happen so you can assess the risk of a failure and see if you
accept the consequence of that.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of Jan Steinman
Sent: Monday, April 21, 2014 10:44 AM
To: [hidden email]
Subject: Re: [EVDL] Charging your EV pack from other batteries?

Electric Motor Werks actually says you can do this with their charger
(http://emotorwerks.com/tech/electronics):

"Both non-PFC and PFC units can be used to charge your battery from a DC
source. This feature can be used to charge one EV from another, to use
the charger with a separate rectifier (e.g., for 3-phase operation),
charger your EV from your solar array / stationary battery, etc. Non-PFC
units can be used with DC input above the voltage of the battery being
charged (up to ~400 VDC)
PFC units can be used with any DC source ~100-400VDC."

Anyone have experience with EMW chargers? I'm considering one, because
my current (hah!) charging method is to charge five batteries at a time
with a 40V/40A lab power supply. That means five days for a full charge
of my 24 batteries. :-(

Jan

> Note that MANY switching power supplies can be run from DC. This means
the best way to charge from another EV MAY be through your charger.
>
> If your charger has a "universal" AC input, such as "110 VAC to 240
VAC," then chances are that the first thing the line sees is a bridge
rectifier, which changes AC into DC. The rectifier will "commutate" your
DC in the proper direction, so you don't even need to worry about
polarity. Most modern chargers are over 95% efficient.
>
> So, the BEST way to assure you get the proper charge for your
batteries from another EV might be to connect your AC charger to the
other EV's battery pack -- assuming it doesn't go over the peak voltage
that the AC line would supply to it. (Generally, 240 * 1.414, or about
340 VDC.)
>
> You probably cannot do this with a charger that has a voltage
selection switch that lets it operate on either 120 VAC or 240 VAC. That
implies that there may be transformer or other AC-specific component in
there. And the charging current available may be reduced by 50%, since
only half the input bridge rectifier is being used.
>
> (If you think you may be doing this often, and have the proper skills
and documentation, you might bypass the input bridge entirely to get
back the full charging current capability.)
>
> Kids, don't try this at home! Unless you're skilled at electronics and
have a schematic, the next step would be to contact your charger's
manufacturer to see if they think this is a good idea! (And for
liability reasons, they likely won't. See if you can talk to one of
their engineers, not a sales droid. And see if you can wrangle
schematics out of them.)
>
:::: Given an infinite source of energy, population growth still
produces an inescapable problem. The problem of the acquisition of
energy is replaced by the problem of its dissipation. -- Garrett Hardin
:::: Jan Steinman, EcoReality Co-op ::::

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Re: Charging your EV pack from other batteries?

EcoReality
In reply to this post by brucedp5
> From: "Cor van de Water" <[hidden email]>
>
> The OP requested charging his boat's 48V pack from his 48V solar bank,
> so I doubt that the EMW charger or other standard 110-240V AC supplies/
> chargers will work on 48V DC.

Thanks. People started talking about cars charging each other, and I forgot the OP's needs.

> Usually things don't fail this badly but you need to be aware of what
> can happen so you can assess the risk of a failure and see if you
> accept the consequence of that.

As I had mentioned, "Kids! Don't try this at home!"

:::: Major crops genetically modified for just two traits — herbicide tolerance and insect resistance — are ravaged by super weeds and secondary pests in the heartland of GMOs as farmers fight a losing battle with more of the same; a fundamental shift to organic farming practices may be the only salvation. -- Mae-Wan Ho
:::: Jan Steinman, EcoReality Co-op ::::

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Re: Charging your EV pack from other batteries?

Dan Baker
Thank you everyone for the replies so far- as hoped lots of fantastic info!
 So it sounds like Cor's idea and Marco's drawing are my best bet.  So I
guess my only other question would be around this charging scheme is would
I need to regulate the charge control once the EV pack reaches full charge
(i.e. prevent overcharging)?   Would I have to implement a timer?
Cor, please yes send me info and pricing on your brick DC/DC module.

Cheers,
Dan


On Mon, Apr 21, 2014 at 9:28 PM, Jan Steinman <[hidden email]> wrote:

> > From: "Cor van de Water" <[hidden email]>
> >
> > The OP requested charging his boat's 48V pack from his 48V solar bank,
> > so I doubt that the EMW charger or other standard 110-240V AC supplies/
> > chargers will work on 48V DC.
>
> Thanks. People started talking about cars charging each other, and I
> forgot the OP's needs.
>
> > Usually things don't fail this badly but you need to be aware of what
> > can happen so you can assess the risk of a failure and see if you
> > accept the consequence of that.
>
> As I had mentioned, "Kids! Don't try this at home!"
>
> :::: Major crops genetically modified for just two traits — herbicide
> tolerance and insect resistance — are ravaged by super weeds and secondary
> pests in the heartland of GMOs as farmers fight a losing battle with more
> of the same; a fundamental shift to organic farming practices may be the
> only salvation. -- Mae-Wan Ho
> :::: Jan Steinman, EcoReality Co-op ::::
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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