Re: [EVDL] badly discharged AGM battery advice

[Cor van de Water via EV]

Good to hear that.
I got 10k miles out of my UB121100 (110 Ah) batteries with my US
Electricar (Chevy S10 factory converted) before the range was
unacceptable.
Cor.

On Sat, Dec 11, 2021 at 4:16 PM Ken Olum via EV  wrote:
>
> Thanks for all the advice.  I seem to have got off lucky.  My chargers
> charged up these batteries without trouble.  Today I discharged my pack
> for 5 hours at 20A.  Both undamaged batteries seemed worse than both
> "damaged" batteries.  By the end of this test, the undamaged batteries
> were down to 11.0V under load and the "damaged" batteries were still at
> 11.2V.  So it seems that nothing is wrong.
>
> Kudos to Universal Power Group for a product at (at least in this case)
> stood up to significant mistreatment.
>
> Ken
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Re: [EVDL] badly discharged AGM battery advice

[Ken Olum via EV]

Thanks for all the advice.  I seem to have got off lucky.  My chargers
charged up these batteries without trouble.  Today I discharged my pack
for 5 hours at 20A.  Both undamaged batteries seemed worse than both
"damaged" batteries.  By the end of this test, the undamaged batteries
were down to 11.0V under load and the "damaged" batteries were still at
11.2V.  So it seems that nothing is wrong.

Kudos to Universal Power Group for a product at (at least in this case)
stood up to significant mistreatment.

Ken
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Re: [EVDL] badly discharged AGM battery advice

[Cor van de Water via EV]

I have reversed UB batteries in the past, in an EV with a *long*
series string of batteries (312V, so 26x UB121100) and if a cell has
been reversed, it loses capacity and thus will reverse earlier next
time. You will find such cells by checking for warmer compartments in
the 6-cell battery cases.
On the other hand, I have also bought new batteries that someone
discharged and then let sit at 0V for a year in their garage.
It took about 3 days of applying voltage before it started drawing any
appreciable current, after that it charged normally.
So, any *smart* battery charger will refuse to resurrect such a battery.
What I do is use a current limited lab supply, for example set for
100mA and 30V, connect to the battery and simply wait.
After a while (and this can be several days) the voltage drops to 12V
because the battery starts charging at more than 100mA.
After that you can use a regular charger, though I like to set the lab
supply for 14.2V at about 0.1C so for a 35Ah battery I can use a small
3 Amp supply.
I keep the battery connected until the current draw at 14.2V becomes
very small, less than 0.1 Amp. No problem to leave it attached to the
battery an extra day.
This revives the battery as much as possible, after that you can test
it in normal operation or with a tester to see its capacity and
determine if you want to continue using it.
Good luck!
Cor.

On Tue, Dec 7, 2021 at 10:42 PM EV List Lackey via EV  wrote:
>
> A 12v battery is considered flat when its open circuit voltage is 11.8
> volts.  Since yours were at ~5 volts, it's fairly likely that you've
> reversed some cells.  That's most definitely not good.
>
> Still, you might get lucky, and it can't hurt to give them a long, slow
> equalizing charge.  Cycle them a few times, and then test their capacity.
> While you're at it, also test the other two for capacity.
>
> If you decide they have enough sock left to give you some use, but are
> definitely less healthy than the others, I recommend building a Lee Hart
> Batt-bridge, so you don't over-discharge and reverse them again.
>
> http://evdl.org/pages/battbridge.html
>
> If they turn out to be at death's door, this might be an ideal time to find
> another chore for the 2 remaining good ones, and treat yourself and your Ox
> to a complete new set.
>
> Some here will probalby suggest that you consider lithium, but I'll leave
> that discussion to them, as I'm not really qualified.
>
> Good luck!  I hope it works out.
>
> David Roden, EVDL moderator & general lackey
>
> To reach me, don't reply to this message; I won't get it.  Use my
> offlist address here : http://evdl.org/help/index.html#supt
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>  Most people here [in the US] don't want an abrupt reshuffling
>  of everything. That's why we've had only one revolution. It's
>  why we've fought off the metric system all these years, and
>  thank heaven we have.
>
>   -- Fox anchor Tucker Carlson
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
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Re: [EVDL] badly discharged AGM battery advice

[EV List Lackey via EV]

A 12v battery is considered flat when its open circuit voltage is 11.8 
volts.  Since yours were at ~5 volts, it's fairly likely that you've 
reversed some cells.  That's most definitely not good.

Still, you might get lucky, and it can't hurt to give them a long, slow 
equalizing charge.  Cycle them a few times, and then test their capacity.  
While you're at it, also test the other two for capacity.

If you decide they have enough sock left to give you some use, but are 
definitely less healthy than the others, I recommend building a Lee Hart 
Batt-bridge, so you don't over-discharge and reverse them again.

http://evdl.org/pages/battbridge.html

If they turn out to be at death's door, this might be an ideal time to find 
another chore for the 2 remaining good ones, and treat yourself and your Ox 
to a complete new set.

Some here will probalby suggest that you consider lithium, but I'll leave 
that discussion to them, as I'm not really qualified.

Good luck!  I hope it works out.

David Roden, EVDL moderator & general lackey

To reach me, don't reply to this message; I won't get it.  Use my 
offlist address here : http://evdl.org/help/index.html#supt

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
 Most people here [in the US] don't want an abrupt reshuffling 
 of everything. That's why we've had only one revolution. It's 
 why we've fought off the metric system all these years, and 
 thank heaven we have.  

  -- Fox anchor Tucker Carlson
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 

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Re: [EVDL] badly discharged AGM battery advice

[(-Phil-) via EV]

The longer any lead-acid battery sits at lower SoCs, the more it
sulphates.  Level of discharge X time, and it's cumulative.   This is also
why it's super important to have the absorption phase to fully charge it,
otherwise it's "not quite charged" and it will still slowly sulphate.

Only way to know is to do a capacity test.


On Tue, Dec 7, 2021 at 6:01 PM Ken Olum via EV  wrote:

> Hi, all.  In my Electric Ox I have 4 12V 135Ah AGM batteries from
> Universal Battery.  I got this set in April 2019, so they've been
> through 3 summers of mowing and two winters of snowblowing (which puts a
> lot more stress on them).  My previous set lasted 10 years, though they
> were showing their age after 7.  When I got the current set, I also
> installed individual very high quality 12V chargers from CTEK, and I was
> hoping for even longer life than the previous set.
>
> However, this fall when I was jacking up the tractor to improve the
> wiring I mistakenly left on the "push" switch that retracts the parking
> brakes.  (There should have a been a warning beeper, but it broke and I
> foolishly did not replace it.)  This draws about 0.7A, but I left it on
> for a long time.  A week?  Two?  Then I disconnected the batteries
> completely without noticing the problem and they sat for a week or two
> like that.  Today I went to reconnect everything and discovered the
> problem.  Only two batteries are affected, because these electric
> retract brakes take 24V.  The affected batteries each read 5V.  I
> connected my charging system and these batteries are charging up now.
>
> The question is what to do now.  How badly do you think they have been
> damaged?  If they now have significantly less capacity than the
> unaffected two, I'm going to have to be very careful that I don't
> overdischarge the bad ones when I'm snowblowing at 130A or so.  There
> also could be a problem caused by the very high inrush current when I
> start my snowblower.  There's no controller, just a contactor to connect
> the batteries to the permanent magnet motor.
>
> I could replace the two damaged batteries, but then they would be out of
> sync the opposite way, at least to some degree.
>
> I have a meter on my dashboard that indicates charge level.  It seems to
> work by measuring the lowest voltage that is seen for some short (but
> nonzero) amount of time.  Maybe this will warn me, if I extrapolate
> properly, that the bad two are getting discharged.
>
> There won't be a problem with charging, at least, because they are
> independent for that.
>
> I'd appreciate any advice.  Thanks.
>
> Ken
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[EVDL] badly discharged AGM battery advice

[Ken Olum via EV]

Hi, all.  In my Electric Ox I have 4 12V 135Ah AGM batteries from
Universal Battery.  I got this set in April 2019, so they've been
through 3 summers of mowing and two winters of snowblowing (which puts a
lot more stress on them).  My previous set lasted 10 years, though they
were showing their age after 7.  When I got the current set, I also
installed individual very high quality 12V chargers from CTEK, and I was
hoping for even longer life than the previous set.

However, this fall when I was jacking up the tractor to improve the
wiring I mistakenly left on the "push" switch that retracts the parking
brakes.  (There should have a been a warning beeper, but it broke and I
foolishly did not replace it.)  This draws about 0.7A, but I left it on
for a long time.  A week?  Two?  Then I disconnected the batteries
completely without noticing the problem and they sat for a week or two
like that.  Today I went to reconnect everything and discovered the
problem.  Only two batteries are affected, because these electric
retract brakes take 24V.  The affected batteries each read 5V.  I
connected my charging system and these batteries are charging up now.

The question is what to do now.  How badly do you think they have been
damaged?  If they now have significantly less capacity than the
unaffected two, I'm going to have to be very careful that I don't
overdischarge the bad ones when I'm snowblowing at 130A or so.  There
also could be a problem caused by the very high inrush current when I
start my snowblower.  There's no controller, just a contactor to connect
the batteries to the permanent magnet motor.

I could replace the two damaged batteries, but then they would be out of
sync the opposite way, at least to some degree.

I have a meter on my dashboard that indicates charge level.  It seems to
work by measuring the lowest voltage that is seen for some short (but
nonzero) amount of time.  Maybe this will warn me, if I extrapolate
properly, that the bad two are getting discharged.

There won't be a problem with charging, at least, because they are
independent for that.

I'd appreciate any advice.  Thanks.

Ken
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