Gel or Flooded batteries

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Gel or Flooded batteries

Spike41
I am gathering some info for a conversion I am about to do.  My first one.

71 VW Bus - Manual Transmission.

Does anyone have any opinions about Gel VS Flooded bateries?  Which is better?  Which lasts longer, provides better performance, etc?

Thanks.

Todd
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Re: Gel or Flooded batteries

Peter VanDerWal
> Does anyone have any opinions about Gel VS Flooded bateries?  Which is
> better?  Which lasts longer, provides better performance, etc?

It really depends on the batteries.
Floodeds are preferred by more people because they are cheaper (typically
both in the short run and the long run)
Floodeds also tend to give slightly more range for the weight.
Gels don't typically like high discharge rates.
However, like with most things, there are exceptions.

Are you sure you're looking at Gel batteries and not AGMs?
AGMs are a sealed battery (technically Valve Regulated) like Gels, but use
a fiberglass mat to absorb the acid instead of a silica gel.

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Re: Gel or Flooded batteries

Mark Grasser
In reply to this post by Spike41
Please don't call the Gel. They are AGMs

Mark Grasser
Eliot, ME


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of Spike41
Sent: Wednesday, July 30, 2008 5:32 PM
To: [hidden email]
Subject: [EVDL] Gel or Flooded batteries


I am gathering some info for a conversion I am about to do.  My first one.

71 VW Bus - Manual Transmission.

Does anyone have any opinions about Gel VS Flooded bateries?  Which is
better?  Which lasts longer, provides better performance, etc?

Thanks.

Todd
--
View this message in context:
http://www.nabble.com/Gel-or-Flooded-batteries-tp18743284p18743284.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

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Re: Gel or Flooded batteries

Zeke Yewdall
Actually, Gel and AGM are different... somehow....  Gel handle cold weather
a little better, and deep cycling, but cannot handle the current levels that
EV's demand.  AGM's handle higher current better.  There was a recent thread
on it...  If you look at the MK battery website, you'll see that they have a
complete line of both Gel and AGM batteries, depending on your application.

Z

On Wed, Jul 30, 2008 at 3:39 PM, Mark Grasser <[hidden email]>wrote:

> Please don't call the Gel. They are AGMs
>
> Mark Grasser
> Eliot, ME
>
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf
> Of Spike41
> Sent: Wednesday, July 30, 2008 5:32 PM
> To: [hidden email]
> Subject: [EVDL] Gel or Flooded batteries
>
>
> I am gathering some info for a conversion I am about to do.  My first one.
>
> 71 VW Bus - Manual Transmission.
>
> Does anyone have any opinions about Gel VS Flooded bateries?  Which is
> better?  Which lasts longer, provides better performance, etc?
>
> Thanks.
>
> Todd
> --
> View this message in context:
> http://www.nabble.com/Gel-or-Flooded-batteries-tp18743284p18743284.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
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>
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>
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Re: Gel or Flooded batteries

Spike41
In reply to this post by Mark Grasser
Absorbed Glass Mat Batteries - Got it.  Thanks for the clarification.    

Thanks.



markgrasser wrote
Please don't call the Gel. They are AGMs

Mark Grasser
Eliot, ME


-----Original Message-----
From: ev-bounces@lists.sjsu.edu [mailto:ev-bounces@lists.sjsu.edu] On Behalf
Of Spike41
Sent: Wednesday, July 30, 2008 5:32 PM
To: ev@lists.sjsu.edu
Subject: [EVDL] Gel or Flooded batteries


I am gathering some info for a conversion I am about to do.  My first one.

71 VW Bus - Manual Transmission.

Does anyone have any opinions about Gel VS Flooded bateries?  Which is
better?  Which lasts longer, provides better performance, etc?

Thanks.

Todd
--
View this message in context:
http://www.nabble.com/Gel-or-Flooded-batteries-tp18743284p18743284.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

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Re: Gel or Flooded batteries

Joseph T.
This is what I recall about batteries from the list.

Flooded:

cheap

durable

will take some newb abuse

heavy

bad peukert number so it can't pull many amps so your car will be slow

can handle repeated deep discharges

AGM:

good peukert number so it'll pull lots of amps and be fast

no watering mess like for flooded batteries

lighter

expensive

need special care (balancers) that they don't get out of balance.
CANNOT be overcharged (that's what balancers are for)

Here is the one thing I am not sure about: can AGMs handle repeated
deep discharges? If you install balancers, then can you do repeated
deep discharges on AGMs since then there will be less overcharging?

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Re: Gel or Flooded batteries

Peter VanDerWal
> This is what I recall about batteries from the list.
>
> Flooded:
> heavy
>
> bad peukert number so it can't pull many amps so your car will be slow

> AGM:
>
> good peukert number so it'll pull lots of amps and be fast
> lighter

"Lighter" and "Heavier" are kind of meaningless here.  You can buy heavy
AGMs and light flooded batteries.
For given energy storage:
at rates less than 1C, flooded batteries tend to lighter than AGMs,
around 1C the weights are similar,
a discharges above 1C AGMs tend to be lighter than floodeds.

Peikerts number isn't directly about how many amps you can pull, it's
about the apparent loss in capacity at higher discharge rates.  They can
make floodeds that can produce as much current as high rate AGMs, but they
don't tend to last long.


> Here is the one thing I am not sure about: can AGMs handle repeated
> deep discharges?

Yes, but it depends on how deep.  If you're doing 100% DoD, most floodeds
and AGMs have about the same rated life cycle, i.e. a couple hundred
cycles give or take.

> If you install balancers, then can you do repeated
> deep discharges on AGMs since then there will be less overcharging?

Deep discharges and overcharging are two different issues.  Both
(either/or) will reduce your cycle life.  Both together will really reduce
your cycle life.

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Re: Gel or Flooded batteries

Doug Weathers
In reply to this post by Mark Grasser
Hey Mark,

Please don't misinform the newbies.  There is such a thing as a Gel
battery.  Instead of letting the electrolyte slosh around in liquid
form like a flooded battery, or absorbing it into a fiberglass mat like
an AGM, a gel battery absorbs the electrolye into a gelling agent.

<http://en.wikipedia.org/wiki/Gel_battery>

DEKA makes a well-regarded line of them.  The original Solectria Force
conversions used them.  They are not so good for energy density, they
are non-spillable, and they tend to have long life.  They're bad at
making large amounts of current, so the successful conversions that use
gel batteries generally use lots of small ones to get a high voltage
pack (which reduces the current draw).

Don Cameron's excellent New Beetle conversion journal talks about how
he decided on his batteries:

<http://www.cameronsoftware.com/ev/EV_BatterySelection.html>

He compared the various battery types and chose gels for his car.


On Jul 30, 2008, at 3:39 PM, Mark Grasser wrote:

> Please don't call the Gel. They are AGMs
>
> Mark Grasser
> Eliot, ME
>
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf
> Of Spike41
> Sent: Wednesday, July 30, 2008 5:32 PM
> To: [hidden email]
> Subject: [EVDL] Gel or Flooded batteries
>
>
> I am gathering some info for a conversion I am about to do.  My first
> one.
>
> 71 VW Bus - Manual Transmission.
>
> Does anyone have any opinions about Gel VS Flooded bateries?  Which is
> better?  Which lasts longer, provides better performance, etc?
>
> Thanks.
>
> Todd
> --
> View this message in context:
> http://www.nabble.com/Gel-or-Flooded-batteries-tp18743284p18743284.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>
--
Doug Weathers
Las Cruces, NM, USA
http://www.gdunge.com/

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Re: Gel or Flooded batteries

MPaulHolmes
In reply to this post by Spike41
I just bought 6 of the biggest Sears Platinum AGM batteries for a little in-town 72v commuter 1971 VW Super Beetle.  I'll let you know how they turn out.  There's a 3 year full replacement warranty on them.  As a side note, they are only 100 amp*hr, but weigh 75 pounds each, and have a Peukert value of 1.09 or so.  ONLY $240 each! Wow, what a deal.
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Re: Gel or Flooded batteries

EVDL Administrator
"Sealed" gel and AGM batteries are actually valve regulated.  That means
that hazardous excess pressure from gassing can be released by pop valves.  
Allegedly the cell caps, if any, aren't removeable; they can't (officially)
be watered even if they should need it.  They make less mess because they're
closed systems, but usually cost more per mile or KM of use, and require
more sophisticated (read : more expensive) charging systems.  You can judge
their state of charge rather approximately by reading their open circuit
voltage.

Flooded or open batteries can release small amounts of acid mist when
charged, may weep electrolyte if the post seals fail, and require periodic
cleaning.  They also need occasional watering.   They usually cost markedly
less than valve regulated batteries per mile or KM of use.  They are more
forgiving of crude chargers.  You can measure their state of charge fairly
accurately with a hydrometer.

In general, gel batteries have the lowest specific power (watts per unit of
weight) of the types mentioned.  My understanding (usual disclaimer : I am
not an electrochemist) is that this is because as the acid in the
electrolyte is depleted in the discharge reaction, it takes longer than in
other designs for the concentrated electrolyte to diffuse in and take its
place.

AGM batteries generally have the highest specific power.  But not all AGMs
are optimized for power, so some are better than others in this regard.

Again generally speaking, flooded batteries have the best specific energy
(watt-hours per unit of weight).  This is because gel and AGM batteries are
often of starved-electrolyte design.  This means the electrolyte goes flat
before the electrodes do, protecting the electrodes from overdischarge.

Again, however, there are exceptions.  Also, because of AGMs' often better
Peukert performance, some will return higher apparent capacity when the
battery is being discharged in a half-hour or less (high performance EVs,
for example).

East Penn Deka Dominator gel batteries were indeed the batteries Solectria
chose for their EVs, after trying several brands of flooded 12v marine
batteries, and AGMs by Hawker.  Dominators work relatively well without
individual battery regulators because their manufacturing tolerances are
unusually close -- that is, the batteries are quite consistent in capacity
and stay fairly so with minimal equalization.  

Also, the Dominators are more electrolyte-starved than most.  If you look at
their manual, cycle life is rated as nearly equal at 80% DOD and 100% DOD.  
That's because, for them, 100% DOD (the electrolyte flat) leaves the
electrodes at about 20% SOC.  This protects the batteries from overdischarge
by careless users.  

The Brusa AC controllers that Solectria used also helped preserve the
batteries by monitoring the pack voltage.  They limited the current to keep
the battery voltage from falling below 1.75 vpc.  Generic DC series motor
controllers, which suit a wide range of input voltages without
configuration, usually aren't able to do this.  AFAIK, Curtis controllers at
least don't.

Gel batteries are generally usable up to about 2C (twice their amp-hour
capacity expressed in amps).   Flooded batteries are typically good to about
3C.  AGMs vary; Concorde batteries, for example, behave a lot like flooded
batteries; Hawkers dish out stupendous currents with aplomb.

David Roden
EVDL Administrator
http://www.evdl.org/


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Re: Gel or Flooded batteries

Joseph T.
Thank you Peter for correcting me.

"If you're doing 100% DoD, most floodeds and AGMs have about the same
rated life cycle, i.e. a couple hundred cycles give or take."

Assuming you have an AGM pack that is given a 60% DOD (that's probably
a pretty typical DOD from an EV) and assuming that all other factors
are fine (good charger, balancers, never pulling a ridiculous number
of amps ect.) how many cycles can you expect from a pack like this?

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Re: Gel or Flooded batteries

AMPrentice
In reply to this post by EVDL Administrator
The plot thickens! great posts and guidance for us newbies
What is required to keep SLA happy and equalized?

EVDL Administrator wrote
"Sealed" gel and AGM batteries are actually valve regulated.  That means
that hazardous excess pressure from gassing can be released by pop valves.  
Allegedly the cell caps, if any, aren't removeable; they can't (officially)
be watered even if they should need it.  They make less mess because they're
closed systems, but usually cost more per mile or KM of use, and require
more sophisticated (read : more expensive) charging systems.  You can judge
their state of charge rather approximately by reading their open circuit
voltage.

Flooded or open batteries can release small amounts of acid mist when
charged, may weep electrolyte if the post seals fail, and require periodic
cleaning.  They also need occasional watering.   They usually cost markedly
less than valve regulated batteries per mile or KM of use.  They are more
forgiving of crude chargers.  You can measure their state of charge fairly
accurately with a hydrometer.

In general, gel batteries have the lowest specific power (watts per unit of
weight) of the types mentioned.  My understanding (usual disclaimer : I am
not an electrochemist) is that this is because as the acid in the
electrolyte is depleted in the discharge reaction, it takes longer than in
other designs for the concentrated electrolyte to diffuse in and take its
place.

AGM batteries generally have the highest specific power.  But not all AGMs
are optimized for power, so some are better than others in this regard.

Again generally speaking, flooded batteries have the best specific energy
(watt-hours per unit of weight).  This is because gel and AGM batteries are
often of starved-electrolyte design.  This means the electrolyte goes flat
before the electrodes do, protecting the electrodes from overdischarge.

Again, however, there are exceptions.  Also, because of AGMs' often better
Peukert performance, some will return higher apparent capacity when the
battery is being discharged in a half-hour or less (high performance EVs,
for example).

East Penn Deka Dominator gel batteries were indeed the batteries Solectria
chose for their EVs, after trying several brands of flooded 12v marine
batteries, and AGMs by Hawker.  Dominators work relatively well without
individual battery regulators because their manufacturing tolerances are
unusually close -- that is, the batteries are quite consistent in capacity
and stay fairly so with minimal equalization.  

Also, the Dominators are more electrolyte-starved than most.  If you look at
their manual, cycle life is rated as nearly equal at 80% DOD and 100% DOD.  
That's because, for them, 100% DOD (the electrolyte flat) leaves the
electrodes at about 20% SOC.  This protects the batteries from overdischarge
by careless users.  

The Brusa AC controllers that Solectria used also helped preserve the
batteries by monitoring the pack voltage.  They limited the current to keep
the battery voltage from falling below 1.75 vpc.  Generic DC series motor
controllers, which suit a wide range of input voltages without
configuration, usually aren't able to do this.  AFAIK, Curtis controllers at
least don't.

Gel batteries are generally usable up to about 2C (twice their amp-hour
capacity expressed in amps).   Flooded batteries are typically good to about
3C.  AGMs vary; Concorde batteries, for example, behave a lot like flooded
batteries; Hawkers dish out stupendous currents with aplomb.

David Roden
EVDL Administrator
http://www.evdl.org/


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Re: Gel or Flooded batteries

Nicolas Drouin
On 7/31/08, AMPrentice <[hidden email]> wrote:
>
> The plot thickens! great posts and guidance for us newbies
> What is required to keep SLA happy and equalized?
>

I'll try to list some of the things I think I have learnt on AGMs from
lurking on the list these past few months.  I would invite everyone to
correct me, because these are the assumptions I'm going on for my
converstion!


1. Do not over-discharge

Unless you have a starved electrolyte battery, (see Dave's post), do
not go below 20% SOC (state of charge).  To really improve
durabillity, do not go below 50% on a regular basis.  So calculate
your daily comute on 50% SOC plus a factor for aging and temperature
compensation, if applicable.

A note on SOC:
Ref: http://www.odysseybatteries.com/battery/pc2150.htm
SOC is measured (estimated!?) at the rate you are discharging them.
Don't use the 20hr rate (say 5 amps continuous for the odyssey pc2150)
to calculate SOC if you are discharging at the 1hr rate (say
67.2amps).
So you can run your EV, at 67.2 amps for 80% of an hour (48minutes).
Or you can run it (well not really) at 5 amps for 80% of 20 hours
(16hours).   Multiply the amps times the time in hours, times the pack
voltage* and you will get your SOC in WHrs.

*A note on voltage sag:
Voltage will sag when amps are drawn, the more you draw, the more it
sags.  So calculating your SOC in WHr, you need to factor in the
voltage sag (unless you can measure, but we're still in the design
phase here...).  Again using the chart reference above: at the 1hr
rate, the battery is putting out 786.1Watts; devide by the amps (67.2)
and you see that it is sagging to 11.7VDC.  At the 20 hour rate, this
is 11.9VDC.

A note on temperature:
Most of the published data seems to be for a temperature controlled
environment.  Good battery data will provide the correction factors to
apply due to temperature variations.  A frozzen battery is useless in
EVs.


2. Do not overcharge
If you drive the voltage too high in the last stage of charging, you
will boil the electrolyte.
In a flooded battery, this is not too bad: a little venting while it
boils, wipe up the mess and top up the battery with distilled water at
the end of the month, perhaps check the specific gravity twice a year,
all is well.
In an AGM, despite being sealed, it will vent once you overpressurise
the 'sealed' case, but you'd have to forcably remove the vents to
refill the electrolyte.  I've seen a post or two go by from the more
adventurous EV'ers trying to recover an old or abused pack, but as a
rule: keep the water in the AGM battery in the first place!  See
charging section below.


3. Charging

Have a quick read of:  http://www.evdl.org/pages/hartcharge.html

Ref: http://soneil.com/Completesets/SPEC1214S(Rev01).042904.pdf

Preferably, use a multi-stage charger as described in the Soneil
reference above and reproduced and edited below.  Note that this
particular soneil charger is probably too small: it will take quite a
while to charge almost any EV pack, and some EV'ers have stated that
too low a charge current may not be good for the battery in the long
run.

Here Soneil is describing charging one battery per charger:

Stage 1: Constant Current Mode (CC):
The charger changes to constant current (its maximum). When the
battery voltage reaches up to 14.7V, the charging stage changes from
CC (Constant Current) to CV (Constant Voltage) mode.

Stage 2: Constant Voltage Mode (CV):
The charger holds the battery at 14.7V and the current slowly reduces
(as the SOC increases). When the current reaches at 0.5CC (CC =
Constant Current), it switches to Standby Voltage Mode.

Stage 3: Standby Voltage Mode:
The charger maintains the battery voltage at 13.8V and current slowly
reduces to zero. Charger can be left connected indefinitely without
harming the battery.

But you will have a 72+VDC string of batteries, probably with one
charger controlling the whole string.  Even if it does have stages:
how do you make sure all the batteries are equalised?
That is, what do you do when one of the batteries in the string
finishes charging before the rest?  If you keep charging it, it will
boil.
You have to force it to have the right voltage by attaching a small
circuit or battery regulator between its poles.  There are commercial
BMS/regulators to do this, but the cheapest solution would be a
home-made voltage clamper such as the one described in many posts in
the archives, search for zenner voltage clamp.  I'll try to summarize:
 You control the voltage over that battery (using a couple zenner
diodes chosen to have the right constant voltage) and when the battery
reaches that current, the diodes bypass the battery and burn off the
aperage using a small light bulb, a resistor is put in parallel with
the bulb incase it burns out you will still have /some/ bypass.
This simple voltage clamp allows you to have a considerably cheaper
charger, that doesn't have to communicate with each battery regulator
in order to decide if it will back off on its total pack voltage, or
current, etc.  Obviously it comes at a cost: there is a trade off in
reliability and sofistication.  But it should extend the life of your
bats by not overcharging any and ensure your total pack performance is
not dragged down by 'the weakest link' since you have some form of
charge equalisation.

Another approach is charge shuttling.
Ref: http://www.geocities.com/sorefeets/balancerland/
If I can summarize this without putting my foot in my mouth it'll be a
miracle...  Have sensing/charging lines with relays on all the bats
and use a programable logic controller to open a relay to connect a
voltmeter to a bat, read the data from the voltmeter via a serial
interface, compare it to other known battery readings, and decide if
it will activate a DC-DC converter, via relays, to take power from the
main high voltage pack in order to recharge a single battery whose
voltage has dropped more than others.


Hoping that didn't contain too much disinformation, cheers,

-Nick
Montreal QC,
www.evalbum.com/1890

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Re: Gel or Flooded batteries

AMPrentice
The plot thickens further and I see that AGMs very short life compared
to Gels makes it clear that although AGMs make big power they last a
very short life. When looking at the Deka range there is 20 dollars in
difference between the 8ggc2 and the 8agc2 and yet the Gel 8ggc2 is
rated for 600 cycles @ 80DOD where the AGM @ 200 making AGMs a
very expensive proposition.

Nick Drouin wrote
On 7/31/08, AMPrentice <darega@yahoo.com> wrote:
>
> The plot thickens! great posts and guidance for us newbies
> What is required to keep SLA happy and equalized?
>

I'll try to list some of the things I think I have learnt on AGMs from
lurking on the list these past few months.  I would invite everyone to
correct me, because these are the assumptions I'm going on for my
converstion!


1. Do not over-discharge

Unless you have a starved electrolyte battery, (see Dave's post), do
not go below 20% SOC (state of charge).  To really improve
durabillity, do not go below 50% on a regular basis.  So calculate
your daily comute on 50% SOC plus a factor for aging and temperature
compensation, if applicable.

A note on SOC:
Ref: http://www.odysseybatteries.com/battery/pc2150.htm
SOC is measured (estimated!?) at the rate you are discharging them.
Don't use the 20hr rate (say 5 amps continuous for the odyssey pc2150)
to calculate SOC if you are discharging at the 1hr rate (say
67.2amps).
So you can run your EV, at 67.2 amps for 80% of an hour (48minutes).
Or you can run it (well not really) at 5 amps for 80% of 20 hours
(16hours).   Multiply the amps times the time in hours, times the pack
voltage* and you will get your SOC in WHrs.

*A note on voltage sag:
Voltage will sag when amps are drawn, the more you draw, the more it
sags.  So calculating your SOC in WHr, you need to factor in the
voltage sag (unless you can measure, but we're still in the design
phase here...).  Again using the chart reference above: at the 1hr
rate, the battery is putting out 786.1Watts; devide by the amps (67.2)
and you see that it is sagging to 11.7VDC.  At the 20 hour rate, this
is 11.9VDC.

A note on temperature:
Most of the published data seems to be for a temperature controlled
environment.  Good battery data will provide the correction factors to
apply due to temperature variations.  A frozzen battery is useless in
EVs.


2. Do not overcharge
If you drive the voltage too high in the last stage of charging, you
will boil the electrolyte.
In a flooded battery, this is not too bad: a little venting while it
boils, wipe up the mess and top up the battery with distilled water at
the end of the month, perhaps check the specific gravity twice a year,
all is well.
In an AGM, despite being sealed, it will vent once you overpressurise
the 'sealed' case, but you'd have to forcably remove the vents to
refill the electrolyte.  I've seen a post or two go by from the more
adventurous EV'ers trying to recover an old or abused pack, but as a
rule: keep the water in the AGM battery in the first place!  See
charging section below.


3. Charging

Have a quick read of:  http://www.evdl.org/pages/hartcharge.html

Ref: http://soneil.com/Completesets/SPEC1214S(Rev01).042904.pdf

Preferably, use a multi-stage charger as described in the Soneil
reference above and reproduced and edited below.  Note that this
particular soneil charger is probably too small: it will take quite a
while to charge almost any EV pack, and some EV'ers have stated that
too low a charge current may not be good for the battery in the long
run.

Here Soneil is describing charging one battery per charger:

Stage 1: Constant Current Mode (CC):
The charger changes to constant current (its maximum). When the
battery voltage reaches up to 14.7V, the charging stage changes from
CC (Constant Current) to CV (Constant Voltage) mode.

Stage 2: Constant Voltage Mode (CV):
The charger holds the battery at 14.7V and the current slowly reduces
(as the SOC increases). When the current reaches at 0.5CC (CC =
Constant Current), it switches to Standby Voltage Mode.

Stage 3: Standby Voltage Mode:
The charger maintains the battery voltage at 13.8V and current slowly
reduces to zero. Charger can be left connected indefinitely without
harming the battery.

But you will have a 72+VDC string of batteries, probably with one
charger controlling the whole string.  Even if it does have stages:
how do you make sure all the batteries are equalised?
That is, what do you do when one of the batteries in the string
finishes charging before the rest?  If you keep charging it, it will
boil.
You have to force it to have the right voltage by attaching a small
circuit or battery regulator between its poles.  There are commercial
BMS/regulators to do this, but the cheapest solution would be a
home-made voltage clamper such as the one described in many posts in
the archives, search for zenner voltage clamp.  I'll try to summarize:
 You control the voltage over that battery (using a couple zenner
diodes chosen to have the right constant voltage) and when the battery
reaches that current, the diodes bypass the battery and burn off the
aperage using a small light bulb, a resistor is put in parallel with
the bulb incase it burns out you will still have /some/ bypass.
This simple voltage clamp allows you to have a considerably cheaper
charger, that doesn't have to communicate with each battery regulator
in order to decide if it will back off on its total pack voltage, or
current, etc.  Obviously it comes at a cost: there is a trade off in
reliability and sofistication.  But it should extend the life of your
bats by not overcharging any and ensure your total pack performance is
not dragged down by 'the weakest link' since you have some form of
charge equalisation.

Another approach is charge shuttling.
Ref: http://www.geocities.com/sorefeets/balancerland/
If I can summarize this without putting my foot in my mouth it'll be a
miracle...  Have sensing/charging lines with relays on all the bats
and use a programable logic controller to open a relay to connect a
voltmeter to a bat, read the data from the voltmeter via a serial
interface, compare it to other known battery readings, and decide if
it will activate a DC-DC converter, via relays, to take power from the
main high voltage pack in order to recharge a single battery whose
voltage has dropped more than others.


Hoping that didn't contain too much disinformation, cheers,

-Nick
Montreal QC,
www.evalbum.com/1890

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Re: Gel or Flooded batteries

EVstuff
In reply to this post by Spike41
I prefer flooded.
1.    You have lots of space.
2.     They are forgiving.
3.     Less expensive.
Tom Meyers

> I am gathering some info for a conversion I am about to do.  My first one.
> 71 VW Bus - Manual Transmission.
Does anyone have any opinions about Gel VS Flooded bateries?  Which is
better?  Which lasts longer, provides better performance, etc?
> Thanks.
> Todd

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Re: Gel or Flooded batteries

Lee Hart
In reply to this post by Joseph T.
Joseph T. wrote:
>> "If you're doing 100% DoD, most floodeds and AGMs have about the same
>> rated life cycle, i.e. a couple hundred cycles give or take."
>
> Assuming you have an AGM pack that is given a 60% DOD (that's probably
> a pretty typical DOD from an EV) and assuming that all other factors
> are fine (good charger, balancers, never pulling a ridiculous number
> of amps etc.) how many cycles can you expect from a pack like this?

Generalizations like these are often misleading. The differences in life
between different types of flooded batteries is huge. A flooded fork
lift battery's life is measured in thousands of cycles; a flooded car
starting battery's life is maybe a dozen cycles. Averaging them together
to say a flooded battery lasts "a couple hundred cycles" is not meaningful.

Likewise, you can find premium AGMs that last far longer than cheap
ones. Averaging them is similarly meaningless.

In the end, you need to compare the data on *specific* batteries, and
not choose between them based on generalizations.

In Joe's case, a 60% DOD is close enough to 80% DOD that you can use the
manufacturer's rated life at 80% DOD as a rough guide. The shallower
discharges (60% vs. 80%) will extend cycle life by perhaps 2:1
(regardless of type).
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in    --    Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Re: Gel or Flooded batteries

Jeff Shanab
In reply to this post by Spike41
If you can live with the lower amps of gel, (ie make sure you have a
high voltage pack and let the controller do current multiplication for
you and or keep the vehicle light.) the gels compared to the orbitals
have 15% more energy in the same space. They weigh more, it is just the
difference in flat plates vs spirals and the space between the spiral
cells.

I was surprised to find pretty good prices and fast moving and fresh
stock on the 8g24mm's here in Fresno. They have changed to all SAE posts
now.
The 1hr rateing is twice the orbitals 1 hr rate. but 53.6 vs 41 lb

My 984lbs of 24 orbitals may go to 24 gels @ 1272 lbs next pack, once I
get a new BMS

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Re: Gel or Flooded batteries

AMPrentice
You are lucky in the US that Gels are much cheaper than here in Oz.
I just calculated that Gels here at double the price will cost 65-70%
the price of the cheapes lithium lifepo4 (not TS).

Jeff Shanab wrote
If you can live with the lower amps of gel, (ie make sure you have a
high voltage pack and let the controller do current multiplication for
you and or keep the vehicle light.) the gels compared to the orbitals
have 15% more energy in the same space. They weigh more, it is just the
difference in flat plates vs spirals and the space between the spiral
cells.

I was surprised to find pretty good prices and fast moving and fresh
stock on the 8g24mm's here in Fresno. They have changed to all SAE posts
now.
The 1hr rateing is twice the orbitals 1 hr rate. but 53.6 vs 41 lb

My 984lbs of 24 orbitals may go to 24 gels @ 1272 lbs next pack, once I
get a new BMS

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Re: Gel or Flooded batteries

AMPrentice
In reply to this post by Nicolas Drouin
I really like Lee Harts´s system the best but Im not EVolved enough to implement it.
If I had the electronic skill, I would not sleep until I have it installed on my EV.
I hope that one day either Lee or someone else would commercialize such a system
for people like me who can work doing something else and use those funds for it.

For now I will go for the Rudman regulators as Im not keen on saving money by making
a cheaper version, when the cost of whats commercially available is trivial.
I would rather put the energy wasted back into the grid but maybe on my next EV if
I learn something or more sinks in then I will hopefully setup the Hart-Beat Balancer :)
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Re: Gel or Flooded batteries

Gary Krysztopik-2


AMPrentice wrote:

> I really like Lee Harts´s system the best but Im not EVolved enough to
> implement it.
> If I had the electronic skill, I would not sleep until I have it installed
> on my EV.
> I hope that one day either Lee or someone else would commercialize such a
> system
> for people like me who can work doing something else and use those funds for
> it.
>
> For now I will go for the Rudman regulators as Im not keen on saving money
> by making
> a cheaper version, when the cost of whats commercially available is trivial.
> I would rather put the energy wasted back into the grid but maybe on my next
> EV if
> I learn something or more sinks in then I will hopefully setup the Hart-Beat
> Balancer :)
>
> -----
> Except from himself and other fellow men,
> Man is the least endangered of all species.     - Me
>  
I got the relay boards from Lee and I'm using them in manual mode for
now and it works great.  I put a bunch of switches and a little DVM on
the box and I just switch thru all the batteries and write the values
down.  I top off the low ones every now and then thru the leads that I
brought out.  It's cheaper and simpler than an automatic system and it
does the job until I add the microcontroller.

--
Gary Krysztopik
www.ZWheelz.com
San Antonio, TX

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