Re: Looking headway completed packs

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Re: Looking headway completed packs

Peakfoto Digital Photo Still n Video
 
Where can I find completed headyway battery packs form china or something?

I'm looking for 36 volts  8-10 ah pack .

most amaercans dealers are spendy .

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Re: Looking headway completed packs

Michael Ross
You should try Alibaba for small packs.  I bought the one linked below and
it seems pretty good so far.

http://www.aliexpress.com/store/product/48V-20Ah-LiFePO4-Battery-1000W-BMS-6A-Charger-FOR-E-BIKE-Free-Shipping/328001_821460991.html

You can also put out an RFQ at Alibaba and get many responses.


On Wed, Dec 18, 2013 at 2:08 PM, Peakfoto Digital Photo Still n Video <
[hidden email]> wrote:

>
> Where can I find completed headyway battery packs form china or something?
>
> I'm looking for 36 volts  8-10 ah pack .
>
> most amaercans dealers are spendy .
>
> _______________________________________________
> 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)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
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Re: Looking headway completed packs

EVDL Administrator
In reply to this post by Peakfoto Digital Photo Still n Video
On 18 Dec 2013 at 11:08, Peakfoto Digital Photo Still n Video wrote:

> Where can I find completed headyway battery packs form china or something?
>
> I'm looking for 36 volts  8-10 ah pack .

It's not Headway, but I've had mostly satisfactory results from
http://www.pingbattery.com.  They offer complete packs with pre-assembled
BMS and included charger.  Got the reference from a couple of the e-bike
forums.

The only problem I've had is that I bought 2 packs and one of the (universal
input) chargers failed when I tried to use it on 240 volts.  I've read that
Ping will often replace failed chargers if contacted, but since I have a
spare, I didn't bother.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: Looking headway completed packs

Michael Ross
OK, its your money.

I have had mine apart and can share images about what's inside and how it
is built. I repackaged it in a coroplast box I made.  I have ideas about
trying to bottom balance it.  I too was weirded out by the separate BMS,
but it is spot on with the balancing.  You can get to all the cell voltages
from an inline connector to the BMS.  The 6 amp charger is fine so far.  I
was skeptical about the capacity as it is only half again heavier than the
10Ah pack I have, but it is at least double the power and it has degraded
less so far.  Seems better in the cold now than the other as well.  Oh
yeah, they gave free air shipping, too.  It was really a great deal.

I priced many packs, including Headway and Ping, and decided to see if the
low cost one had any merit.  It has been a success.  It has a lot more
energy density as it is a pack of 96 181650 cells.  The pack I have made
with way 32120 cells is not holding up as well.  I believe those are
Headway cells.  I think if you are going to be picky you should be looking
at CALB and Thundersky.  I have heard that Headway are actually rebranded
from some other supplier, however that could be apocryphal.  Very hard to
tell with Chinese supplies.

But, I wasn't suggesting this pack in particular, I was suggesting you use
Alibaba and try the RFQ function.  After buying this pack, I am not sure if
Ping are really worth the rather large extra cost.




On Wed, Dec 18, 2013 at 4:09 PM, EVDL Administrator <[hidden email]> wrote:

> On 18 Dec 2013 at 11:08, Peakfoto Digital Photo Still n Video wrote:
>
> > Where can I find completed headyway battery packs form china or
> something?
> >
> > I'm looking for 36 volts  8-10 ah pack .
>
> It's not Headway, but I've had mostly satisfactory results from
> http://www.pingbattery.com.  They offer complete packs with pre-assembled
> BMS and included charger.  Got the reference from a couple of the e-bike
> forums.
>
> The only problem I've had is that I bought 2 packs and one of the
> (universal
> input) chargers failed when I tried to use it on 240 volts.  I've read that
> Ping will often replace failed chargers if contacted, but since I have a
> spare, I didn't bother.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
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> reach me.  To send a private message, please obtain my
> email address from the webpage http://www.evdl.org/help/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

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Re: Looking headway completed packs

EVDL Administrator
On 18 Dec 2013 at 16:29, Michael Ross wrote:

> After buying this pack, I am not sure if Ping are really worth the
> rather large extra cost.

I don't have anything to compare them to, but mine are now almost 2 years
old and still going strong.  I would (will) buy from them again.  My only
gripe is the cost for shipping, but I have to say they were packaged VERY
well.

I built mine into custom aluminum boxes with little smoked-acrylic windows
to show off the blinky LEDs on the BMSes.

The capacity was a bit low at first, 9.something ah for a 10ah rated
battery, but at last test last summer, it was around 10.5ah.  That's to ~21
volts for a 24 nominal volt battery, when my 24v inverter shuts down.

I try to charge until the first LED comes on, not really needing maximum
capacity.  I let them balance (all 8 LEDs) every 5 or 6 charges.  Even at
that, from 1 LED to 6-7 on is usually less than a minute.  Often there one
or two slight stragglers that continue to blink briefly for another few
minutes after that, then it's (presumably) balanced.

These are obviously too small for road EVs, but are fairly widely used in E-
bikes and scooters.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: Looking headway completed packs

Travis
In reply to this post by Peakfoto Digital Photo Still n Video
Buy direct from headway.
http://www.headway-cn.com/index.html <http://www.headway-cn.com/index.html>

Be warned, by the time you pay for shipping and any associated fees, you get a
pack that has little or no warranty. Don't expect China to help deal with any
warranty claims.

After all is said and done, 38120S Headway cells aren't that much better than
some CALB cells. Depending on how many Ah you need, if you can do 40/60/100,
then CALB are a much better deal. You don't have to worry about all that
bussbar.

This is coming from someone who's built a few large packs using headway. I'd do
it differently today.


> On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> <[hidden email]> wrote:
>
>
> Where can I find completed headyway battery packs form china or something?
>
> I'm looking for 36 volts 8-10 ah pack .
>
> most amaercans dealers are spendy .
>
> _______________________________________________
> 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: Looking headway completed packs

Peakfoto Digital Photo Still n Video
In reply to this post by Peakfoto Digital Photo Still n Video
 I'm looking for higher charge rates than ping. they can only do .5 c or something.
headways can do 1C plus easy.

also heaways can be repaired my most any one , not ping .
 

>>> I agree you need to charge/ load balance

most setups don't HVC , rest then, HVC , ..come back on again till finished .
then charger i got form my headways does that automaticly.
 

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Re: Looking headway completed packs

Michael Ross
In reply to this post by EVDL Administrator
Yes, they are small packs.  My EV is an eVelomobile you might say.  (Don't
sniff at this it works well, I commute 25 miles each way on it.  I could
buy two of them for what many pay for just the batteries in a car
conversion.  And I get the exercise I need too.)  The motor is for an
E-bike 1HP.  Uses an RC controller.

I have two packs one at 10Ah 48V is probably Headways, the other is the
20Ah 48V pack I mention from Alibaba.

FWIW they give this spec:  Maximum Discharge Current   30 AH (BMS Set 1.5C
1500W ) Peak:60A (2000W)

I think charging and discharging rates are usually the same.  Is that a bad
assumption?

Inside the 10Ah pack is nicely constructed, the BMS looks well made.  I did
not like that the connector plates were torqued barely hand tight.  I
brought them up to spec (I forget exactly, maybe 35 in lb).

Here is a link to an album with images for the unwrapped packs in case you
are curious.
Can anyone confirm the cells look like Headways cells?
 https://picasaweb.google.com/100767276460953028406/OTELF



On Wed, Dec 18, 2013 at 5:09 PM, EVDL Administrator <[hidden email]> wrote:

> On 18 Dec 2013 at 16:29, Michael Ross wrote:
>
> > After buying this pack, I am not sure if Ping are really worth the
> > rather large extra cost.
>
> I don't have anything to compare them to, but mine are now almost 2 years
> old and still going strong.  I would (will) buy from them again.  My only
> gripe is the cost for shipping, but I have to say they were packaged VERY
> well.
>
> I built mine into custom aluminum boxes with little smoked-acrylic windows
> to show off the blinky LEDs on the BMSes.
>
> The capacity was a bit low at first, 9.something ah for a 10ah rated
> battery, but at last test last summer, it was around 10.5ah.  That's to ~21
> volts for a 24 nominal volt battery, when my 24v inverter shuts down.
>
> I try to charge until the first LED comes on, not really needing maximum
> capacity.  I let them balance (all 8 LEDs) every 5 or 6 charges.  Even at
> that, from 1 LED to 6-7 on is usually less than a minute.  Often there one
> or two slight stragglers that continue to blink briefly for another few
> minutes after that, then it's (presumably) balanced.
>
> These are obviously too small for road EVs, but are fairly widely used in
> E-
> bikes and scooters.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> Note: mail sent to "evpost" and "etpost" addresses will not
> reach me.  To send a private message, please obtain my
> email address from the webpage http://www.evdl.org/help/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
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> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

EVDL Administrator
On 19 Dec 2013 at 11:31, Michael Ross wrote:

> Maximum Discharge Current   30 AH

You must mean 30 amps, no?  Saying "the current is 30 amp hours" is kind of
like saying "my speed is 25 miles."  The unit makes no sense in the context.

> Here is a link to an album with images for the unwrapped packs in case
> you are curious. Can anyone confirm the cells look like Headways cells?
> https://picasaweb.google.com/100767276460953028406/OTELF 

They look like other pictures I've seen of Headway cells, but I suppose they
could be knockoffs.

You have an intriguing little EV there.  Is it in the EV Album?

David Roden - Akron, Ohio, USA
EVDL Administrator

= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
EVDL Information: http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Note: mail sent to "evpost" and "etpost" addresses will not
reach me.  To send a private message, please obtain my
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Re: Looking headway completed packs

Michael Ross
You know this is one of the problems buying from China - the specs are
always suspect.  I just copied and pasted.  Clearly 1.5 C of 20Ah is going
to be 30A in an hour.  30 Ah / 1 h = 30Amps.


On Thu, Dec 19, 2013 at 1:51 PM, EVDL Administrator <[hidden email]> wrote:

> On 19 Dec 2013 at 11:31, Michael Ross wrote:
>
> > Maximum Discharge Current   30 AH
>
> You must mean 30 amps, no?  Saying "the current is 30 amp hours" is kind of
> like saying "my speed is 25 miles."  The unit makes no sense in the
> context.
>
> > Here is a link to an album with images for the unwrapped packs in case
> > you are curious. Can anyone confirm the cells look like Headways cells?
> > https://picasaweb.google.com/100767276460953028406/OTELF
>
> They look like other pictures I've seen of Headway cells, but I suppose
> they
> could be knockoffs.
>
> You have an intriguing little EV there.  Is it in the EV Album?
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> Note: mail sent to "evpost" and "etpost" addresses will not
> reach me.  To send a private message, please obtain my
> email address from the webpage http://www.evdl.org/help/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
> _______________________________________________
> 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)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

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Re: Looking headway completed packs

gtyler54
In reply to this post by Travis
I am repairing a headway battery from china at the moment, made a deal with
Conhismotor who supplied it, they supply the new cells and I do the labour.
I usually buy  from evlithium. Dealing with china is different, freight
costs are so high that you have to consider the cost of sending a pack back
carefully, it is often not worth it. This pack has 48 38120L cells, groups
of 3 in parallel, 16 groups in series. I see Headway spec says up to 5% per
month self discharge, but most of the pack has close to zero. The BMS can
only bypass 50 or 100ma or so (it has SM resistors for this!), so it stands
little chance of equallising 5% per month difference. All the cells may be
in spec, but the battery does not work

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of emf-evdl
Sent: Thursday, 19 December 2013 12:32 p.m.
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Looking headway completed packs

Buy direct from headway.
http://www.headway-cn.com/index.html <http://www.headway-cn.com/index.html>

Be warned, by the time you pay for shipping and any associated fees, you get
a pack that has little or no warranty. Don't expect China to help deal with
any warranty claims.

After all is said and done, 38120S Headway cells aren't that much better
than some CALB cells. Depending on how many Ah you need, if you can do
40/60/100, then CALB are a much better deal. You don't have to worry about
all that bussbar.

This is coming from someone who's built a few large packs using headway. I'd
do it differently today.


> On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> <[hidden email]> wrote:
>
>
> Where can I find completed headyway battery packs form china or something?
>
> I'm looking for 36 volts 8-10 ah pack .
>
> most amaercans dealers are spendy .
>
> _______________________________________________
> 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: Looking headway completed packs

gtyler54
In reply to this post by Travis
After working on this 48V pack of 48 cells I am inclined to agree that fewer
Calb cells is more attractive, you can get them from Evlithium too. The
headway cells (38120P with screw terminals) I bought from them were cheaper
than buying direct from headway. The ones in this pack I am working on have
welded tabs, not friendly to work on. You can get plastic holders for these
cells that you build up like Lego, those with the straps and screw terminals
are much nicer to work on, neat too.
        I did look at calb, but the 38120P cells have a 20C discharge rate,
to get the same allowable discharge current from calb you need something
above 100Ah I think it was. I have been looking at R/C packs from Hobbyking,
you can get these in up to 130C discharge rating. I had a Diahatsu charade I
was driving 5 kms to work and the same back, so I wanted a low capacity,
high rate battery. I had health problems so did not finish the project
though.

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of emf-evdl
Sent: Thursday, 19 December 2013 12:32 p.m.
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Looking headway completed packs

Buy direct from headway.
http://www.headway-cn.com/index.html <http://www.headway-cn.com/index.html>

Be warned, by the time you pay for shipping and any associated fees, you get
a pack that has little or no warranty. Don't expect China to help deal with
any warranty claims.

After all is said and done, 38120S Headway cells aren't that much better
than some CALB cells. Depending on how many Ah you need, if you can do
40/60/100, then CALB are a much better deal. You don't have to worry about
all that bussbar.

This is coming from someone who's built a few large packs using headway. I'd
do it differently today.


> On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> <[hidden email]> wrote:
>
>
> Where can I find completed headyway battery packs form china or something?
>
> I'm looking for 36 volts 8-10 ah pack .
>
> most amaercans dealers are spendy .
>
> _______________________________________________
> 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: Looking headway completed packs

Michael Ross
In reply to this post by gtyler54
Have you ever seen a cell not connected to some parasitic load that loses
5% in a month?

I think this is just a CYA, not a real spec.

Over a month from 110/30 to 11/30 my 38120 pack lost and average of
0.0018125V/3.3430625*100% = 0.05%

Over the last two weeks of it only 0.007% was lost.

The 18650 pack lost 0.128% (0.004 V) over a 2 week period.

Both started from a fresh charge.

Since then I have been using them so there is no longer static period.

I think when you charge them overmuch it is more like an electrostatic
charge on top that diffuses over a bit of time and thermal cycling (a
settling period).  Once that is gone you are reading the actual cell
voltage and there is almost no self discharge.

Something to consider: 0.001V is really not so easy to read and most of us,
I bet, don't manage lab temperature, or even get periodic calibrations.
 Neither our instruments or the environment supports this sort of accuracy.

These single digit millivolt readings are very likely just noise, not real
numbers worth paying attention to.  Many people who are more knowledgeable
(people who maintain calibrations and good lab practice needed for small
signal measurement) than I, say there is no self discharge; there is no
theory or evidence for how it could occur.  It does not exist within
a properly made Li cell.




On Thu, Dec 19, 2013 at 2:48 PM, George Tyler <[hidden email]> wrote:

> I am repairing a headway battery from china at the moment, made a deal with
> Conhismotor who supplied it, they supply the new cells and I do the labour.
> I usually buy  from evlithium. Dealing with china is different, freight
> costs are so high that you have to consider the cost of sending a pack back
> carefully, it is often not worth it. This pack has 48 38120L cells, groups
> of 3 in parallel, 16 groups in series. I see Headway spec says up to 5% per
> month self discharge, but most of the pack has close to zero. The BMS can
> only bypass 50 or 100ma or so (it has SM resistors for this!), so it stands
> little chance of equallising 5% per month difference. All the cells may be
> in spec, but the battery does not work
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf
> Of emf-evdl
> Sent: Thursday, 19 December 2013 12:32 p.m.
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Looking headway completed packs
>
> Buy direct from headway.
> http://www.headway-cn.com/index.html <http://www.headway-cn.com/index.html
> >
>
> Be warned, by the time you pay for shipping and any associated fees, you
> get
> a pack that has little or no warranty. Don't expect China to help deal with
> any warranty claims.
>
> After all is said and done, 38120S Headway cells aren't that much better
> than some CALB cells. Depending on how many Ah you need, if you can do
> 40/60/100, then CALB are a much better deal. You don't have to worry about
> all that bussbar.
>
> This is coming from someone who's built a few large packs using headway.
> I'd
> do it differently today.
>
>
> > On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> > <[hidden email]> wrote:
> >
> >
> > Where can I find completed headyway battery packs form china or
> something?
> >
> > I'm looking for 36 volts 8-10 ah pack .
> >
> > most amaercans dealers are spendy .
> >
> > _______________________________________________
> > 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)
> >
> -------------- next part --------------
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> /attachment.htm>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
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> (http://groups.yahoo.com/group/NEDRA)
>
>
> _______________________________________________
> 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)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

Cor van de Water
In reply to this post by gtyler54
One word of warning,
I have ordered a set of (admittedly cheap) LiPoly packs for my eBike
from them 2 years ago.
Since power requirements was not high, I settled for 10C packs of 4S
10Ah.
When I received my 4 packs, one had a cell that was either completely
self-discharged or was never initially charged, it was at 0V.
Another pack had a different issue, I think it was a wire for the
BMS connector was not properly crimped or something like that.
The internal resistance of the cells was such that in order to get the
current required for 10C, you would need to charge to max cutoff (4.2V)
and then load the cells to 10C which would send them to around (and some
below) the min cutoff voltage (2.5V). In other words - these were at
best
2 or 3C and even then there was more than 2x spread in voltage drop from
internal resistance between cells.
So, be aware of getting something from a company that can be a
hit-and-miss
as evidenced by many similar stories on the RC lists - they might have
improved since then, this was 2 years ago. I wasted $200 on a combined
25.6V 20Ah pack that although serviceable in my eBike due to low power
requirement and my hand-balancing of the cells, would be unusable when
attempted to be used at actual 10C or unsupervised charging.

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 George Tyler
Sent: Thursday, December 19, 2013 12:12 PM
To: 'emf-evdl'; 'Electric Vehicle Discussion List'
Subject: Re: [EVDL] Looking headway completed packs

After working on this 48V pack of 48 cells I am inclined to agree that
fewer
Calb cells is more attractive, you can get them from Evlithium too. The
headway cells (38120P with screw terminals) I bought from them were
cheaper
than buying direct from headway. The ones in this pack I am working on
have
welded tabs, not friendly to work on. You can get plastic holders for
these
cells that you build up like Lego, those with the straps and screw
terminals
are much nicer to work on, neat too.
        I did look at calb, but the 38120P cells have a 20C discharge
rate,
to get the same allowable discharge current from calb you need something
above 100Ah I think it was. I have been looking at R/C packs from
Hobbyking,
you can get these in up to 130C discharge rating. I had a Diahatsu
charade I
was driving 5 kms to work and the same back, so I wanted a low capacity,
high rate battery. I had health problems so did not finish the project
though.

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf
Of emf-evdl
Sent: Thursday, 19 December 2013 12:32 p.m.
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Looking headway completed packs

Buy direct from headway.
http://www.headway-cn.com/index.html
<http://www.headway-cn.com/index.html>

Be warned, by the time you pay for shipping and any associated fees, you
get
a pack that has little or no warranty. Don't expect China to help deal
with
any warranty claims.

After all is said and done, 38120S Headway cells aren't that much better
than some CALB cells. Depending on how many Ah you need, if you can do
40/60/100, then CALB are a much better deal. You don't have to worry
about
all that bussbar.

This is coming from someone who's built a few large packs using headway.
I'd
do it differently today.


> On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> <[hidden email]> wrote:
>
>
> Where can I find completed headyway battery packs form china or
something?

>
> I'm looking for 36 volts 8-10 ah pack .
>
> most amaercans dealers are spendy .
>
> _______________________________________________
> 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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_______________________________________________
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Re: Looking headway completed packs

Michael Ross
Cor,

Who is them exactly?  I am not sure in the context of this thread who you
are referring to.

Thx,

Mike


On Thu, Dec 19, 2013 at 3:41 PM, Cor van de Water <[hidden email]> wrote:

> One word of warning,
> I have ordered a set of (admittedly cheap) LiPoly packs for my eBike
> from them 2 years ago.
> Since power requirements was not high, I settled for 10C packs of 4S
> 10Ah.
> When I received my 4 packs, one had a cell that was either completely
> self-discharged or was never initially charged, it was at 0V.
> Another pack had a different issue, I think it was a wire for the
> BMS connector was not properly crimped or something like that.
> The internal resistance of the cells was such that in order to get the
> current required for 10C, you would need to charge to max cutoff (4.2V)
> and then load the cells to 10C which would send them to around (and some
> below) the min cutoff voltage (2.5V). In other words - these were at
> best
> 2 or 3C and even then there was more than 2x spread in voltage drop from
> internal resistance between cells.
> So, be aware of getting something from a company that can be a
> hit-and-miss
> as evidenced by many similar stories on the RC lists - they might have
> improved since then, this was 2 years ago. I wasted $200 on a combined
> 25.6V 20Ah pack that although serviceable in my eBike due to low power
> requirement and my hand-balancing of the cells, would be unusable when
> attempted to be used at actual 10C or unsupervised charging.
>
> 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 George Tyler
> Sent: Thursday, December 19, 2013 12:12 PM
> To: 'emf-evdl'; 'Electric Vehicle Discussion List'
> Subject: Re: [EVDL] Looking headway completed packs
>
> After working on this 48V pack of 48 cells I am inclined to agree that
> fewer
> Calb cells is more attractive, you can get them from Evlithium too. The
> headway cells (38120P with screw terminals) I bought from them were
> cheaper
> than buying direct from headway. The ones in this pack I am working on
> have
> welded tabs, not friendly to work on. You can get plastic holders for
> these
> cells that you build up like Lego, those with the straps and screw
> terminals
> are much nicer to work on, neat too.
>         I did look at calb, but the 38120P cells have a 20C discharge
> rate,
> to get the same allowable discharge current from calb you need something
> above 100Ah I think it was. I have been looking at R/C packs from
> Hobbyking,
> you can get these in up to 130C discharge rating. I had a Diahatsu
> charade I
> was driving 5 kms to work and the same back, so I wanted a low capacity,
> high rate battery. I had health problems so did not finish the project
> though.
>

--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

Cor van de Water
In reply to this post by Michael Ross
Michael,
You are quoting voltage, which is not a linear indicator of charge.
As quoted before, between 20 and 80% some battery chemistries like
LiFePO4 might only change 1mV for each % of SoC. Other chemistries react
differently and in particular LiPoly and similar have a more linear
relation between voltage and SoC. But still not completely linear so you
can still not do the calculation that you did.

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 Michael Ross
Sent: Thursday, December 19, 2013 12:38 PM
To: [hidden email]; Electric Vehicle Discussion List
Subject: Re: [EVDL] Looking headway completed packs

Have you ever seen a cell not connected to some parasitic load that
loses
5% in a month?

I think this is just a CYA, not a real spec.

Over a month from 110/30 to 11/30 my 38120 pack lost and average of
0.0018125V/3.3430625*100% = 0.05%

Over the last two weeks of it only 0.007% was lost.

The 18650 pack lost 0.128% (0.004 V) over a 2 week period.

Both started from a fresh charge.

Since then I have been using them so there is no longer static period.

I think when you charge them overmuch it is more like an electrostatic
charge on top that diffuses over a bit of time and thermal cycling (a
settling period).  Once that is gone you are reading the actual cell
voltage and there is almost no self discharge.

Something to consider: 0.001V is really not so easy to read and most of
us,
I bet, don't manage lab temperature, or even get periodic calibrations.
 Neither our instruments or the environment supports this sort of
accuracy.

These single digit millivolt readings are very likely just noise, not
real
numbers worth paying attention to.  Many people who are more
knowledgeable
(people who maintain calibrations and good lab practice needed for small
signal measurement) than I, say there is no self discharge; there is no
theory or evidence for how it could occur.  It does not exist within
a properly made Li cell.




On Thu, Dec 19, 2013 at 2:48 PM, George Tyler <[hidden email]> wrote:

> I am repairing a headway battery from china at the moment, made a deal
with
> Conhismotor who supplied it, they supply the new cells and I do the
labour.
> I usually buy  from evlithium. Dealing with china is different,
freight
> costs are so high that you have to consider the cost of sending a pack
back
> carefully, it is often not worth it. This pack has 48 38120L cells,
groups
> of 3 in parallel, 16 groups in series. I see Headway spec says up to
5% per
> month self discharge, but most of the pack has close to zero. The BMS
can
> only bypass 50 or 100ma or so (it has SM resistors for this!), so it
stands
> little chance of equallising 5% per month difference. All the cells
may be

> in spec, but the battery does not work
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf
> Of emf-evdl
> Sent: Thursday, 19 December 2013 12:32 p.m.
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Looking headway completed packs
>
> Buy direct from headway.
> http://www.headway-cn.com/index.html
<http://www.headway-cn.com/index.html
> >
>
> Be warned, by the time you pay for shipping and any associated fees,
you
> get
> a pack that has little or no warranty. Don't expect China to help deal
with
> any warranty claims.
>
> After all is said and done, 38120S Headway cells aren't that much
better
> than some CALB cells. Depending on how many Ah you need, if you can do
> 40/60/100, then CALB are a much better deal. You don't have to worry
about
> all that bussbar.
>
> This is coming from someone who's built a few large packs using
headway.

> I'd
> do it differently today.
>
>
> > On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> > <[hidden email]> wrote:
> >
> >
> > Where can I find completed headyway battery packs form china or
> something?
> >
> > I'm looking for 36 volts 8-10 ah pack .
> >
> > most amaercans dealers are spendy .
> >
> > _______________________________________________
> > 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)
> >
> -------------- next part --------------
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1e5

> /attachment.htm>
> _______________________________________________
> 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)
>
>
> _______________________________________________
> 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)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A.
Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

Cor van de Water
In reply to this post by Michael Ross
Oops, sorry I should have made clear that after reading the previous
post, I triggered on the name HobbyKing...

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 Michael Ross
Sent: Thursday, December 19, 2013 12:46 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Looking headway completed packs

Cor,

Who is them exactly?  I am not sure in the context of this thread who
you
are referring to.

Thx,

Mike


On Thu, Dec 19, 2013 at 3:41 PM, Cor van de Water <[hidden email]>
wrote:

> One word of warning,
> I have ordered a set of (admittedly cheap) LiPoly packs for my eBike
> from them 2 years ago.
> Since power requirements was not high, I settled for 10C packs of 4S
> 10Ah.
> When I received my 4 packs, one had a cell that was either completely
> self-discharged or was never initially charged, it was at 0V.
> Another pack had a different issue, I think it was a wire for the
> BMS connector was not properly crimped or something like that.
> The internal resistance of the cells was such that in order to get the
> current required for 10C, you would need to charge to max cutoff
(4.2V)
> and then load the cells to 10C which would send them to around (and
some
> below) the min cutoff voltage (2.5V). In other words - these were at
> best
> 2 or 3C and even then there was more than 2x spread in voltage drop
from

> internal resistance between cells.
> So, be aware of getting something from a company that can be a
> hit-and-miss
> as evidenced by many similar stories on the RC lists - they might have
> improved since then, this was 2 years ago. I wasted $200 on a combined
> 25.6V 20Ah pack that although serviceable in my eBike due to low power
> requirement and my hand-balancing of the cells, would be unusable when
> attempted to be used at actual 10C or unsupervised charging.
>
> 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 George Tyler
> Sent: Thursday, December 19, 2013 12:12 PM
> To: 'emf-evdl'; 'Electric Vehicle Discussion List'
> Subject: Re: [EVDL] Looking headway completed packs
>
> After working on this 48V pack of 48 cells I am inclined to agree that
> fewer
> Calb cells is more attractive, you can get them from Evlithium too.
The

> headway cells (38120P with screw terminals) I bought from them were
> cheaper
> than buying direct from headway. The ones in this pack I am working on
> have
> welded tabs, not friendly to work on. You can get plastic holders for
> these
> cells that you build up like Lego, those with the straps and screw
> terminals
> are much nicer to work on, neat too.
>         I did look at calb, but the 38120P cells have a 20C discharge
> rate,
> to get the same allowable discharge current from calb you need
something
> above 100Ah I think it was. I have been looking at R/C packs from
> Hobbyking,
> you can get these in up to 130C discharge rating. I had a Diahatsu
> charade I
> was driving 5 kms to work and the same back, so I wanted a low
capacity,
> high rate battery. I had health problems so did not finish the project
> though.
>

--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A.
Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

Michael Ross
In reply to this post by Cor van de Water
Cor,

I think that a lack of change in voltage is an indicator of lack change in
state of charge - the best one can do at any rate.  People talk about
LiFePO4 cells self discharging, but I I don't think it happens.  Maybe
other formulations do, I don't know about that.

The non-linearity does make voltage very insensitive as a measure of SOC.
 I get that.

But when you have battery and someone says, "it is self discharging," I am
not sure what else to do beside actually draining it down to zero and
integrating the amps to know it is losing charge; and even then the knowing
is tenuous if the discharge was small.

If you can't read tiny voltage well, and most of us cannot with our
handheld meters, then there is a very good chance that talk of self
discharge is just a reaction to measurement noise.




On Thu, Dec 19, 2013 at 3:47 PM, Cor van de Water <[hidden email]> wrote:

> Michael,
> You are quoting voltage, which is not a linear indicator of charge.
> As quoted before, between 20 and 80% some battery chemistries like
> LiFePO4 might only change 1mV for each % of SoC. Other chemistries react
> differently and in particular LiPoly and similar have a more linear
> relation between voltage and SoC. But still not completely linear so you
> can still not do the calculation that you did.
>
> 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 Michael Ross
> Sent: Thursday, December 19, 2013 12:38 PM
> To: [hidden email]; Electric Vehicle Discussion List
> Subject: Re: [EVDL] Looking headway completed packs
>
> Have you ever seen a cell not connected to some parasitic load that
> loses
> 5% in a month?
>
> I think this is just a CYA, not a real spec.
>
> Over a month from 110/30 to 11/30 my 38120 pack lost and average of
> 0.0018125V/3.3430625*100% = 0.05%
>
> Over the last two weeks of it only 0.007% was lost.
>
> The 18650 pack lost 0.128% (0.004 V) over a 2 week period.
>
> Both started from a fresh charge.
>
> Since then I have been using them so there is no longer static period.
>
> I think when you charge them overmuch it is more like an electrostatic
> charge on top that diffuses over a bit of time and thermal cycling (a
> settling period).  Once that is gone you are reading the actual cell
> voltage and there is almost no self discharge.
>
> Something to consider: 0.001V is really not so easy to read and most of
> us,
> I bet, don't manage lab temperature, or even get periodic calibrations.
>  Neither our instruments or the environment supports this sort of
> accuracy.
>
> These single digit millivolt readings are very likely just noise, not
> real
> numbers worth paying attention to.  Many people who are more
> knowledgeable
> (people who maintain calibrations and good lab practice needed for small
> signal measurement) than I, say there is no self discharge; there is no
> theory or evidence for how it could occur.  It does not exist within
> a properly made Li cell.
>
>
>
>
> On Thu, Dec 19, 2013 at 2:48 PM, George Tyler <[hidden email]> wrote:
>
> > I am repairing a headway battery from china at the moment, made a deal
> with
> > Conhismotor who supplied it, they supply the new cells and I do the
> labour.
> > I usually buy  from evlithium. Dealing with china is different,
> freight
> > costs are so high that you have to consider the cost of sending a pack
> back
> > carefully, it is often not worth it. This pack has 48 38120L cells,
> groups
> > of 3 in parallel, 16 groups in series. I see Headway spec says up to
> 5% per
> > month self discharge, but most of the pack has close to zero. The BMS
> can
> > only bypass 50 or 100ma or so (it has SM resistors for this!), so it
> stands
> > little chance of equallising 5% per month difference. All the cells
> may be
> > in spec, but the battery does not work
> >
> > -----Original Message-----
> > From: [hidden email] [mailto:[hidden email]] On
> > Behalf
> > Of emf-evdl
> > Sent: Thursday, 19 December 2013 12:32 p.m.
> > To: Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Looking headway completed packs
> >
> > Buy direct from headway.
> > http://www.headway-cn.com/index.html
> <http://www.headway-cn.com/index.html
> > >
> >
> > Be warned, by the time you pay for shipping and any associated fees,
> you
> > get
> > a pack that has little or no warranty. Don't expect China to help deal
> with
> > any warranty claims.
> >
> > After all is said and done, 38120S Headway cells aren't that much
> better
> > than some CALB cells. Depending on how many Ah you need, if you can do
> > 40/60/100, then CALB are a much better deal. You don't have to worry
> about
> > all that bussbar.
> >
> > This is coming from someone who's built a few large packs using
> headway.
> > I'd
> > do it differently today.
> >
> >
> > > On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> > > <[hidden email]> wrote:
> > >
> > >
> > > Where can I find completed headyway battery packs form china or
> > something?
> > >
> > > I'm looking for 36 volts 8-10 ah pack .
> > >
> > > most amaercans dealers are spendy .
> > >
> > > _______________________________________________
> > > 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)
> > >
> > -------------- next part --------------
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> > <
> >
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> 1e5
> > /attachment.htm>
> > _______________________________________________
> > 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)
> >
> >
> > _______________________________________________
> > 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)
> >
> >
>
>
> --
> Put this question to yourself: should I use everyone else to attain
> happiness, or should I help others gain happiness?
> *Dalai Lama *
>
> Tell me what it is you plan to do
> With your one wild and precious life?
> Mary Oliver, "The summer day."
>
> To invent, you need a good imagination and a pile of junk.
> Thomas A.
> Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
>
> A public-opinion poll is no substitute for thought.
> *Warren Buffet*
>
> Michael E. Ross
> (919) 550-2430 Land
> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
> Phone
> (919) 631-1451 Cell
> (919) 513-0418 Desk
>
> [hidden email]
> <[hidden email]>
> -------------- next part --------------
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> _______________________________________________
> 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)
>
> _______________________________________________
> 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)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

Cor van de Water
Hi Michael,
I have several large format LiFePO4 cells sitting in my garage.
One set I charged to 3.0V (to stay *under* the flat area of the SoC
curve)
and I am measuring the self-discharge of these cells with my old
Fluke 77 series II multimeter which has a range of 3.25V reading in mV.
So, discharging these cells from about 10% SoC, I can tell you that just
letting them sit will show self-discharge - less at low temp (close to
the freezing in my unheated garage now) and more when it was warmer.

I am also measuring several cells that are being charged at very low
current (about 15mA at the moment) and I see them all creep up and
hitting a knee
at about 3.225V where the voltage rise suddenly slows down even though
the charging goes on with the same current, so apparently that point is
the start of the flat area in the SoC curve when charging.

Of course you are free to think what you want, but I can tell you from
measurements that LiFePO4 cells *do* self discharge. Not much, but they
do and it is not equal between cells either.

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 Michael Ross
Sent: Thursday, December 19, 2013 2:15 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Looking headway completed packs

Cor,

I think that a lack of change in voltage is an indicator of lack change
in
state of charge - the best one can do at any rate.  People talk about
LiFePO4 cells self discharging, but I I don't think it happens.  Maybe
other formulations do, I don't know about that.

The non-linearity does make voltage very insensitive as a measure of
SOC.
 I get that.

But when you have battery and someone says, "it is self discharging," I
am
not sure what else to do beside actually draining it down to zero and
integrating the amps to know it is losing charge; and even then the
knowing
is tenuous if the discharge was small.

If you can't read tiny voltage well, and most of us cannot with our
handheld meters, then there is a very good chance that talk of self
discharge is just a reaction to measurement noise.




On Thu, Dec 19, 2013 at 3:47 PM, Cor van de Water <[hidden email]>
wrote:

> Michael,
> You are quoting voltage, which is not a linear indicator of charge.
> As quoted before, between 20 and 80% some battery chemistries like
> LiFePO4 might only change 1mV for each % of SoC. Other chemistries
react
> differently and in particular LiPoly and similar have a more linear
> relation between voltage and SoC. But still not completely linear so
you

> can still not do the calculation that you did.
>
> 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 Michael Ross
> Sent: Thursday, December 19, 2013 12:38 PM
> To: [hidden email]; Electric Vehicle Discussion List
> Subject: Re: [EVDL] Looking headway completed packs
>
> Have you ever seen a cell not connected to some parasitic load that
> loses
> 5% in a month?
>
> I think this is just a CYA, not a real spec.
>
> Over a month from 110/30 to 11/30 my 38120 pack lost and average of
> 0.0018125V/3.3430625*100% = 0.05%
>
> Over the last two weeks of it only 0.007% was lost.
>
> The 18650 pack lost 0.128% (0.004 V) over a 2 week period.
>
> Both started from a fresh charge.
>
> Since then I have been using them so there is no longer static period.
>
> I think when you charge them overmuch it is more like an electrostatic
> charge on top that diffuses over a bit of time and thermal cycling (a
> settling period).  Once that is gone you are reading the actual cell
> voltage and there is almost no self discharge.
>
> Something to consider: 0.001V is really not so easy to read and most
of
> us,
> I bet, don't manage lab temperature, or even get periodic
calibrations.
>  Neither our instruments or the environment supports this sort of
> accuracy.
>
> These single digit millivolt readings are very likely just noise, not
> real
> numbers worth paying attention to.  Many people who are more
> knowledgeable
> (people who maintain calibrations and good lab practice needed for
small
> signal measurement) than I, say there is no self discharge; there is
no
> theory or evidence for how it could occur.  It does not exist within
> a properly made Li cell.
>
>
>
>
> On Thu, Dec 19, 2013 at 2:48 PM, George Tyler <[hidden email]> wrote:
>
> > I am repairing a headway battery from china at the moment, made a
deal
> with
> > Conhismotor who supplied it, they supply the new cells and I do the
> labour.
> > I usually buy  from evlithium. Dealing with china is different,
> freight
> > costs are so high that you have to consider the cost of sending a
pack
> back
> > carefully, it is often not worth it. This pack has 48 38120L cells,
> groups
> > of 3 in parallel, 16 groups in series. I see Headway spec says up to
> 5% per
> > month self discharge, but most of the pack has close to zero. The
BMS
> can
> > only bypass 50 or 100ma or so (it has SM resistors for this!), so it
> stands
> > little chance of equallising 5% per month difference. All the cells
> may be
> > in spec, but the battery does not work
> >
> > -----Original Message-----
> > From: [hidden email] [mailto:[hidden email]]
On

> > Behalf
> > Of emf-evdl
> > Sent: Thursday, 19 December 2013 12:32 p.m.
> > To: Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Looking headway completed packs
> >
> > Buy direct from headway.
> > http://www.headway-cn.com/index.html
> <http://www.headway-cn.com/index.html
> > >
> >
> > Be warned, by the time you pay for shipping and any associated fees,
> you
> > get
> > a pack that has little or no warranty. Don't expect China to help
deal
> with
> > any warranty claims.
> >
> > After all is said and done, 38120S Headway cells aren't that much
> better
> > than some CALB cells. Depending on how many Ah you need, if you can
do

> > 40/60/100, then CALB are a much better deal. You don't have to worry
> about
> > all that bussbar.
> >
> > This is coming from someone who's built a few large packs using
> headway.
> > I'd
> > do it differently today.
> >
> >
> > > On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n
Video

> > > <[hidden email]> wrote:
> > >
> > >
> > > Where can I find completed headyway battery packs form china or
> > something?
> > >
> > > I'm looking for 36 volts 8-10 ah pack .
> > >
> > > most amaercans dealers are spendy .
> > >
> > > _______________________________________________
> > > 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)
> > >
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL:
> > <
> >
>
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> 1e5
> > /attachment.htm>
> > _______________________________________________
> > 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)
> >
> >
> > _______________________________________________
> > 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)
> >
> >
>
>
> --
> Put this question to yourself: should I use everyone else to attain
> happiness, or should I help others gain happiness?
> *Dalai Lama *
>
> Tell me what it is you plan to do
> With your one wild and precious life?
> Mary Oliver, "The summer day."
>
> To invent, you need a good imagination and a pile of junk.
> Thomas A.
>
Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

>
> A public-opinion poll is no substitute for thought.
> *Warren Buffet*
>
> Michael E. Ross
> (919) 550-2430 Land
> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
> Phone
> (919) 631-1451 Cell
> (919) 513-0418 Desk
>
> [hidden email]
> <[hidden email]>
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL:
>
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> 7898/attachment.htm>
> _______________________________________________
> 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)
>
> _______________________________________________
> 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)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A.
Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Looking headway completed packs

Peter Gabrielsson
In reply to this post by Michael Ross
I've measured self discharge, I've got access very expensive equipment for
doing so since I work in the EV industry. Lithium cells self discharge, all
cells do. It gets worse with age, wear and tear, cheapo Chinese cells are
not exempt from this.

What Cor is doing is a valid way to estimate self discharge since the
voltage gradient at low SOC is rather steep, it gives a good estimate of
what is going on. Self discharge is worse at higher voltage for
understandable reasons.





On Thu, Dec 19, 2013 at 2:15 PM, Michael Ross <[hidden email]>wrote:

> Cor,
>
> I think that a lack of change in voltage is an indicator of lack change in
> state of charge - the best one can do at any rate.  People talk about
> LiFePO4 cells self discharging, but I I don't think it happens.  Maybe
> other formulations do, I don't know about that.
>
> The non-linearity does make voltage very insensitive as a measure of SOC.
>  I get that.
>
> But when you have battery and someone says, "it is self discharging," I am
> not sure what else to do beside actually draining it down to zero and
> integrating the amps to know it is losing charge; and even then the knowing
> is tenuous if the discharge was small.
>
> If you can't read tiny voltage well, and most of us cannot with our
> handheld meters, then there is a very good chance that talk of self
> discharge is just a reaction to measurement noise.
>
>
>
>
> On Thu, Dec 19, 2013 at 3:47 PM, Cor van de Water <[hidden email]>
> wrote:
>
> > Michael,
> > You are quoting voltage, which is not a linear indicator of charge.
> > As quoted before, between 20 and 80% some battery chemistries like
> > LiFePO4 might only change 1mV for each % of SoC. Other chemistries react
> > differently and in particular LiPoly and similar have a more linear
> > relation between voltage and SoC. But still not completely linear so you
> > can still not do the calculation that you did.
> >
> > 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 Michael Ross
> > Sent: Thursday, December 19, 2013 12:38 PM
> > To: [hidden email]; Electric Vehicle Discussion List
> > Subject: Re: [EVDL] Looking headway completed packs
> >
> > Have you ever seen a cell not connected to some parasitic load that
> > loses
> > 5% in a month?
> >
> > I think this is just a CYA, not a real spec.
> >
> > Over a month from 110/30 to 11/30 my 38120 pack lost and average of
> > 0.0018125V/3.3430625*100% = 0.05%
> >
> > Over the last two weeks of it only 0.007% was lost.
> >
> > The 18650 pack lost 0.128% (0.004 V) over a 2 week period.
> >
> > Both started from a fresh charge.
> >
> > Since then I have been using them so there is no longer static period.
> >
> > I think when you charge them overmuch it is more like an electrostatic
> > charge on top that diffuses over a bit of time and thermal cycling (a
> > settling period).  Once that is gone you are reading the actual cell
> > voltage and there is almost no self discharge.
> >
> > Something to consider: 0.001V is really not so easy to read and most of
> > us,
> > I bet, don't manage lab temperature, or even get periodic calibrations.
> >  Neither our instruments or the environment supports this sort of
> > accuracy.
> >
> > These single digit millivolt readings are very likely just noise, not
> > real
> > numbers worth paying attention to.  Many people who are more
> > knowledgeable
> > (people who maintain calibrations and good lab practice needed for small
> > signal measurement) than I, say there is no self discharge; there is no
> > theory or evidence for how it could occur.  It does not exist within
> > a properly made Li cell.
> >
> >
> >
> >
> > On Thu, Dec 19, 2013 at 2:48 PM, George Tyler <[hidden email]> wrote:
> >
> > > I am repairing a headway battery from china at the moment, made a deal
> > with
> > > Conhismotor who supplied it, they supply the new cells and I do the
> > labour.
> > > I usually buy  from evlithium. Dealing with china is different,
> > freight
> > > costs are so high that you have to consider the cost of sending a pack
> > back
> > > carefully, it is often not worth it. This pack has 48 38120L cells,
> > groups
> > > of 3 in parallel, 16 groups in series. I see Headway spec says up to
> > 5% per
> > > month self discharge, but most of the pack has close to zero. The BMS
> > can
> > > only bypass 50 or 100ma or so (it has SM resistors for this!), so it
> > stands
> > > little chance of equallising 5% per month difference. All the cells
> > may be
> > > in spec, but the battery does not work
> > >
> > > -----Original Message-----
> > > From: [hidden email] [mailto:[hidden email]] On
> > > Behalf
> > > Of emf-evdl
> > > Sent: Thursday, 19 December 2013 12:32 p.m.
> > > To: Electric Vehicle Discussion List
> > > Subject: Re: [EVDL] Looking headway completed packs
> > >
> > > Buy direct from headway.
> > > http://www.headway-cn.com/index.html
> > <http://www.headway-cn.com/index.html
> > > >
> > >
> > > Be warned, by the time you pay for shipping and any associated fees,
> > you
> > > get
> > > a pack that has little or no warranty. Don't expect China to help deal
> > with
> > > any warranty claims.
> > >
> > > After all is said and done, 38120S Headway cells aren't that much
> > better
> > > than some CALB cells. Depending on how many Ah you need, if you can do
> > > 40/60/100, then CALB are a much better deal. You don't have to worry
> > about
> > > all that bussbar.
> > >
> > > This is coming from someone who's built a few large packs using
> > headway.
> > > I'd
> > > do it differently today.
> > >
> > >
> > > > On December 18, 2013 at 2:08 PM Peakfoto Digital Photo Still n Video
> > > > <[hidden email]> wrote:
> > > >
> > > >
> > > > Where can I find completed headyway battery packs form china or
> > > something?
> > > >
> > > > I'm looking for 36 volts 8-10 ah pack .
> > > >
> > > > most amaercans dealers are spendy .
> > > >
> > > > _______________________________________________
> > > > 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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> > > _______________________________________________
> > > 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)
> > >
> > >
> > > _______________________________________________
> > > 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)
> > >
> > >
> >
> >
> > --
> > Put this question to yourself: should I use everyone else to attain
> > happiness, or should I help others gain happiness?
> > *Dalai Lama *
> >
> > Tell me what it is you plan to do
> > With your one wild and precious life?
> > Mary Oliver, "The summer day."
> >
> > To invent, you need a good imagination and a pile of junk.
> > Thomas A.
> > Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
> >
> > A public-opinion poll is no substitute for thought.
> > *Warren Buffet*
> >
> > Michael E. Ross
> > (919) 550-2430 Land
> > (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
> > Phone
> > (919) 631-1451 Cell
> > (919) 513-0418 Desk
> >
> > [hidden email]
> > <[hidden email]>
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> > _______________________________________________
> > 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)
> >
> > _______________________________________________
> > 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)
> >
> >
>
>
> --
> Put this question to yourself: should I use everyone else to attain
> happiness, or should I help others gain happiness?
> *Dalai Lama *
>
> Tell me what it is you plan to do
> With your one wild and precious life?
> Mary Oliver, "The summer day."
>
> To invent, you need a good imagination and a pile of junk.
> Thomas A. Edison<
> http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
>
> A public-opinion poll is no substitute for thought.
> *Warren Buffet*
>
> Michael E. Ross
> (919) 550-2430 Land
> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
> Phone
> (919) 631-1451 Cell
> (919) 513-0418 Desk
>
> [hidden email]
> <[hidden email]>
> -------------- next part --------------
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> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
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> http://groups.yahoo.com/group/NEDRA)
>
>


--
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