# Re: [EVDL] Lead acid battery issues



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

You are drawing your 120V pack down to 60V?
Way to go! You'll murder that pack in no time.

Some of your problem is the cold, Lead-Acids don't perform well when cold
and can loose 50% or more of their available capacity.
The other problem is, if you are routinely drawing a 120V pack below 110V,
you are killing it. Your pack is probably half dead already.

>
> I'm not sure it might be the 20 - 40F temperature here now
> or the fact I'm running AGM batteries but currently my voltage
> is dropping from 125v to 85v at a 300 amp draw & worse when
> my resting voltage is 123 volts, it sags all the way down into the 60s=E2=
=80=99.
> This is after only traveling half the miles as when it=E2=80=99s in the s=
ummer
> here.
> The voltage sag I am seeing was happening in the summer at 50% DOD too
> but that was after I had driven 25 miles. Now I get that issue after just
> 10
> - 12 miles.
> Either way it=E2=80=99s is occurring at 50% DOD.
> The batteries are Trojan AGM31 series & have always behaved this way.
> Trojan says they don=E2=80=99t recommend this battery for EV use anymore =
(thanks
> to
> me).
> They did a few tests that they hadn=E2=80=99t performed before, after I r=
eported
> my
> problems
> and said they had the same results. Something about the =E2=80=9Celectron=
s not
> being
> able to
> transfer fast enough through the glass mat material after high current use
> etc=E2=80=A6
> You=E2=80=99d be better off using FLA batteries for your application=E2=
=80=9D.
> So I'm not sure if I't my battery model, brand, type or FLA vs AGM issue.
> I've had some friends with ODYSSEY & Optimas report the same problem.
> Neal
>
>


> > EVDL Administrator wrote:
> >>
> >> On 14 Jan 2008 at 13:51, shred wrote:
> >>
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*



> On 15 Jan 2008 at 7:41, shred wrote:
> 
> > my voltage
> > is dropping from 125v to 85v at a 300 amp draw & worse when
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

Hey Peter,
It will come down as far as 60 volts when under high current draw.
When you say 
"The other problem is, if you are routinely drawing a 120V pack below 110V,
you are killing it."
Do you mean resting voltage or under a load?
My resting voltage is never under 123 volts.
Neal

You are drawing your 120V pack down to 60V?
Way to go! You'll murder that pack in no time.

Some of your problem is the cold, Lead-Acids don't perform well when cold
and can loose 50% or more of their available capacity.
The other problem is, if you are routinely drawing a 120V pack below 110V,
you are killing it. Your pack is probably half dead already.
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*



> Mark Eidson wrote:
> 
> > What do you mean by drawing the pack down? I can see that if
> > you discharge a 120V pack to 60V there is a problem, but
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*



> shred wrote:
> 
> > When you say
> > "The other problem is, if you are routinely drawing a 120V
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

Hey Peter,
It will come down as far as 60 volts when under high current draw.
When you say 
"The other problem is, if you are routinely drawing a 120V pack below 110V,
you are killing it."
Do you mean resting voltage or under a load?
My resting voltage is never under 123 volts.
Neal

You are drawing your 120V pack down to 60V?
Way to go! You'll murder that pack in no time.

Some of your problem is the cold, Lead-Acids don't perform well when cold
and can loose 50% or more of their available capacity.
The other problem is, if you are routinely drawing a 120V pack below 110V,
you are killing it. Your pack is probably half dead already.
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

He means under load. Since a 12 volt lead acid battery is really 6 2 volt cells, anytime you take it under 10 volts you run the risk of completely reversing a cell which will ruin that cell(5 cells coud be at 2 volts and one completely flat). Just because you are under 10 volts does not mean you have reveresed a cell. Even at 6 volts, all 6 cells could be sitting at 1 volt each, but you have no way of knowing without monitoring each cell individually. The drag racing folks routinely abuse their batteries with very high current draws and sag them to these levels, but they purposely pick batteries with a track record of being able to stand up to this abuse and have found the limits by going past the limits from time to time.

The type of batteries most on this list use in their conversions, and the typical current draws most conversions require have shown that people who report the type of battery sag you are reporting are usually murdering their batteries. This is a very common occurence and one that most people learn through experience. Once you let a whole pack sag that far down it is likely that at least one of your 60 cells has been reveresed and will no longer perform well. This leads to even further battery sag which leads to more cell reversals and eventually you have ruined your whole pack.

damon


> Date: Tue, 15 Jan 2008 11:10:18 -0800
> From: [email protected]
> To: [email protected]
> Subject: Re: [EVDL] Lead acid battery issues
>
>
> Hey Peter,
> It will come down as far as 60 volts when under high current draw.
> When you say
> "The other problem is, if you are routinely drawing a 120V pack below 110V,
> you are killing it."
> Do you mean resting voltage or under a load?
> My resting voltage is never under 123 volts.
> Neal
>
> You are drawing your 120V pack down to 60V?
> Way to go! You'll murder that pack in no time.
>
> Some of your problem is the cold, Lead-Acids don't perform well when cold
> and can loose 50% or more of their available capacity.
> The other problem is, if you are routinely drawing a 120V pack below 110V,
> you are killing it. Your pack is probably half dead already.
> --
> View this message in context: http://www.nabble.com/Fw%3A-Emailing%3A-Specification-form.doc-tp14807911s25542p14844943.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

What do you mean by drawing the pack down? I can see that if you
discharge a 120V pack to 60V there is a problem, but momentary high
current loads that draw the pack down should not be a problem, right?
me

The resting pack voltage will be say 125 volts but when I draw say 380
battery amps the voltage can drop as low as 65-75 volts. 
This problem seems to be much worse when the ambient air temp has been in
the 20's or 30's all night.
Neal
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

What do you mean by drawing the pack down? I can see that if you
discharge a 120V pack to 60V there is a problem, but momentary high
current loads that draw the pack down should not be a problem, right?
me

The resting pack voltage will be say 125 volts but when I draw say 380
battery amps the voltage can drop as low as 65-75 volts. 
This problem seems to be much worse when the ambient air temp has been in
the 20's or 30's all night.
Neal
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

I have seen this EV and the one thing that jumped out at me was the little 
bitty charger for these big batteries.
I wonder if they could be suffering from undercharging? Have they ever had 
an equalize? (An AGM equalize)
I myself put a $20 Lowes digital voltmeter on Each of my Eagle Pitcher 
Batteries so I can see exactly what they are doing on both charge and 
discharge.
We put a lot of money into our batteries, give them each a name and get to 
know them.
Jack.
----- Original Message ----- 
From: "shred" <[email protected]>
To: <[email protected]>
Sent: Tuesday, January 15, 2008 5:34 PM
Subject: Re: [EVDL] Lead acid battery issues


>
>
> What do you mean by drawing the pack down? I can see that if you
> discharge a 120V pack to 60V there is a problem, but momentary high
> current loads that draw the pack down should not be a problem, right?
> me
>
> The resting pack voltage will be say 125 volts but when I draw say 380
> battery amps the voltage can drop as low as 65-75 volts.
> This problem seems to be much worse when the ambient air temp has been in
> the 20's or 30's all night.
> Neal
> -- 
> View this message in context: 
> http://www.nabble.com/Fw%3A-Emailing%3A-Specification-form.doc-tp14807911s25542p14845209.html
> Sent from the Electric Vehicle Discussion List mailing list archive at 
> Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

I meant under ANY load, and I should have said 105V.

Freshly charged batteries that are new, or very well equalized can
possibly survive getting drawn down to 60V (on a nominal 120V pack).
But it's not a good idea.

Routinely drawing the pack down this low will pretty much guaranty that
one or more cells get's reversed. This will drastically shorten that
cells life (if not killing it outright).

If you want your pack to survive for the longest possible time, do not
draw it down below 105V. Brief draws down to perhaps 90V when the pack is
fiarly full are ok, but the problem with this is you get into the habit of
doing it and when the pack get's older even 90V might reverse a cell.

Of course once the pack is worn out and won't perform while staying above
105V, well all bets are off. You might as well abuse it since it doesn't
have long to live anyway.

Of course if you don't mind replacing your batteries every year (or less),
you can do pretty much whatever you want to them.
>
> Hey Peter,
> It will come down as far as 60 volts when under high current draw.
> When you say
> "The other problem is, if you are routinely drawing a 120V pack below
> 110V,
> you are killing it."
> Do you mean resting voltage or under a load?
> My resting voltage is never under 123 volts.
> Neal
>
> You are drawing your 120V pack down to 60V?
> Way to go! You'll murder that pack in no time.
>
> Some of your problem is the cold, Lead-Acids don't perform well when cold
> and can loose 50% or more of their available capacity.
> The other problem is, if you are routinely drawing a 120V pack below 110V,
> you are killing it. Your pack is probably half dead already.
> --
> View this message in context:
> http://www.nabble.com/Fw%3A-Emailing%3A-Specification-form.doc-tp14807911s25542p14844943.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

These batteries are 14 months old & still in prorated warranty. 
I've all ready had 3 replaced for free before the first 8 months. 
The problem is when the battery pack is full it won't sag below 110. 
When it's down to say 70 % SOC in this weather it won't produce the amperage
And then to voltage falls.
I need to test each battery I think I have a bad one. 
I had one test a little week about 2 months ago.
Thanks for all the help!
Neal


I meant under ANY load, and I should have said 105V.

Freshly charged batteries that are new, or very well equalized can
possibly survive getting drawn down to 60V (on a nominal 120V pack).
But it's not a good idea.

Routinely drawing the pack down this low will pretty much guaranty that
one or more cells get's reversed. This will drastically shorten that
cells life (if not killing it outright).

If you want your pack to survive for the longest possible time, do not
draw it down below 105V. Brief draws down to perhaps 90V when the pack is
fiarly full are ok, but the problem with this is you get into the habit of
doing it and when the pack get's older even 90V might reverse a cell.

Of course once the pack is worn out and won't perform while staying above
105V, well all bets are off. You might as well abuse it since it doesn't
have long to live anyway.

Of course if you don't mind replacing your batteries every year (or less),
you can do pretty much whatever you want to them.

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

This is from Trojan's maintenance page.
Percentage of Charge Specific Gravity Corrected to 
80o F Open-Circuit Voltage 
100% 12.73 
90% 12.62 
80% 12.50 
70% 12.37 
60% 12.24 
50% 12.10 
40% 11.96 
30% 11.81 
20% 11.66 
10% 11.513 
TABLE 1. State of charge as related to specific gravity and 
open circuit voltage








> Roger Stockton wrote:
> >
> > shred wrote:
> >
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

I have looked at the voltage of each battery on discharge but not after
charging.
That's an idea to try. I have never eq'ed them. Trojan says not to EQ their
AGM batteries.
My charger has a lot of room voltage wise. 
I can charge up to 170 volts. 
But only at 11 amps max. 
Too low??
Neal



> Jack Knopf wrote:
> >
> > I have seen this EV and the one thing that jumped out at me was the little
> > bitty charger for these big batteries.
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

good data

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*



> Roger Stockton <[email protected]> wrote:
> 
> >
> > I think the original poster's problem is primarily associated with cold batteries; my AGMs show a similarly huge voltage sag when cold (well, perhaps not quite that bad, but 80-90V under load when cold and fully charged is possible).
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

I hope you're not charging that 120 volt pack to 170 volts!

There's charging info on the Trojan website and a toll-free number for tech support if you have questions. Ideally you'll change Absorption voltage as a function of temperature.

The voltage versus SOC numbers you posted are true at a specific temperature and after a rest of several hours i.e. no change in state due to current flow.

Finally: are you sure that you're getting "true" voltage readings? Is it possible your voltmeter isn't accurate?

good luck



----- Original Message ----
From: shred <[email protected]>
To: [email protected]
Sent: Wednesday, January 16, 2008 12:00:14 AM
Subject: Re: [EVDL] Lead acid battery issues



I have looked at the voltage of each battery on discharge but not after
charging.
That's an idea to try. I have never eq'ed them. Trojan says not to EQ
their
AGM batteries.
My charger has a lot of room voltage wise. 
I can charge up to 170 volts. 
But only at 11 amps max. 
Too low??
Neal



> Jack Knopf wrote:
> >
> > I have seen this EV and the one thing that jumped out at me was the
> little
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

I've used 2 different good volt meters to check voltage.
My point was that my charger is adjustable from 70 to 170 volts & 1 to 11
amps.
I know the correct charge voltages for my batteries and even use temperature
compensation.
This was a reply to Jack who was asking is my charger had enough output for
my batteries.
I think 11 amps would be enough to bring my batteries up to full charge.
Neal




> Frank John wrote:
> >
> > I hope you're not charging that 120 volt pack to 170 volts!
> >
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*



> shred wrote:
> 
> > This is from Trojan's maintenance page.
> > Percentage of Charge Specific Gravity Corrected to 80o F
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*

Roger,
I belive what you say is correct.
In fact I always wondered why I could drive 7 miles and still my voltage
reading for the pack would be at or above the Trojan 100% number of 12.73. 
That didn't seem right. 
So I asked them about their chart.
Of course they said it was correct.
Anyway thanks for your information. 
Neal


I would not go by these values. I believe that if you find the right person
at Trojan to ask, you will discover that the "state of charge" referred to
is in regard to the theoretical energy remaining in the active material, and
you cannot actually fully deplete the active material in practical EV use,
at least not without harming the battery.

Basically, in order to reach an OCV in the mid to low 11's you'd need to
discharge your battery at a very low rate, much lower than would allow you
to use your EV.

I work for a battery charger manufacturer, and have run many
charge/discharge tests. I can assure you that if you discharge your
batteries at a current useful for EV operation until they reach 1.75V/cell
(100%DOD/0%SOC *at that load*), or 10.5V/12V module, that when you remove
the load, the voltage will very rapidly jump back up near 12V OCV, and this
is at a practical 0%SOC.

For instance, discharging a set of 80Ah AGMs at 25A (already a very low
current relative to typical EV discharge levels) until 1.75V/cell
(10.5V/battery), the OCV rapidly returns to ~11.9V when the load is removed. 
(For users of floodies, the same holds true: after fully discharging a
healthy pack of flooded 6Vs to 1.75V/cell at 75A, the OCV quickly jumps back
over 1.95V/cell very rapidly and stabilises at about the same 1.98V/cell
(11.9V/12V block) as in the AGM test.) Going by this Trojan chart, you
might be mislead into believing these batteries are at 40%SOC rather than
0%.

You will have removed fewer Ah than the nominal (C/20) rating of the
battery, and the manufacturer may explain that the active material inside
your batteries is actually still at 20-30%SOC, but this information is of
little value to you because you cannot remove that remaining energy except
at currents far too small to allow your EV to operate.

If you neglect the voltage under load and discharge your batteries until
they no longer recover above the low-mid 11's OCV it is almost certain that
you will permanently damage one or more cells.

I also have an EV with a 120V string of AGMs, and I've logged the pack
behaviour over enough trips that I can say with confidence that when my pack
only springs back to 123V OCV when I let off the throttle, it is basically
empty. At this point, it will sag to 1.6V/cell or so under heavy load (in
warm-to-mild, not cold temps), well below the 1.75V/cell threshold
corresponding to 100%DOD. Trojan's table would have you believe that my
battery is only about 55% discharged at this point, but I know full well
that it will be permanently damamged if I push it much further and that even
pushing it this far is shortening its life.

Cheers,

Roger.


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Lead acid battery issues*



> shred wrote:
> 
> > I belive what you say is correct.
> > In fact I always wondered why I could drive 7 miles and still
> ...


----------

