1 - 1 of 1 Posts

#### EVDL List

· Registered
Joined
·
72,624 Posts
Discussion Starter · ·
Re: [EVDL] How much does OCV 1 hr after charge and voltage at fullcharge change for o

Hello Steve,

Sometimes old batteries will not charge any higher at a very low rate, or it
seems like that. Just turn up the current knob a notch. A full charge
battery should be at a resting voltage of 6.37 volts at a specific gravity
of 1.277 volts which is consider 100% SOC.

Normally a battery should be charge at least at 2.5 percent of the
ampere-hour rating of the battery. On a 200 ah battery that would be 5
amps. As the battery approaches 100% the charge ampere should drop to 2.5%
of the ah of a new battery. A old battery because of increase resistance
may not drop below 10 amps if you are charging at the normal 10% rate of the
ah of the battery or this would be 20 amps for a 200 ah battery. The final
charge voltage should be about 6.4 volts after the charger is turn off and
then after 12 hours the voltage should be between 6.37V to 6.4 volts.

Apply a little load to them and if they drop to below 6.26 volts which is in
the 80% SOC range, then you could charge them more if you want to.

As my battery pack age about 8.5 years, I normally stop charging at about
80% SOC, because it was not cost effective to charge them any more, because
the remaining 10 to 20% took too long. I was only driving not more than 2
miles a day anyway.

Roland

----- Original Message -----
From: "Steve Powers" <[email protected]>
To: "ev" <[email protected]>
Sent: Sunday, September 26, 2010 3:20 PM
Subject: [EVDL] How much does OCV 1 hr after charge and voltage at
fullcharge change for old batts

> I have a set of old batteries, 6 V flooded Golf Cart batts. They are
> probably 5-7 years old. Not cycled much though. Probably have 1-2k miles
> on them. Maybe even less. They were in an EV that was sitting. Anyway,
> I removed them and put them in my other car. I am charging them now. The
> other car is only 72 V, so I took the best 12 out of the 20 from the other
> car. I used a very slow charge rate, about 3 Amps. I used the BC-20, set
> for max voltage of 7.5 V / batt (90 V total) and a charge rate of 3 Amps.
> I don't plan to actually go that high though. I have been charging them
> for a while now, and the voltage is slowly going up, as expected. They
> are pretty well in balance. Supposedly, I should stop around 7.2 V /
> battery (86.4 V). But, the batteries are aged, and Lee's infortion on PBA
> batts in the library says I may never get there. So, when do I stop? How
> do I know I am getting a full charge without overcharging them? I don't
> want to
> undercharge them either. I am watching for gassing and keeping the
> charge rate very low. But, I'm not sure what to expect. The batts
> haven't been cycled in at least 2.5 years. Just due to time constraints,
> I'll probably have to stop the charge in a few hours, and I expect the
> pack to be about 82.5 V at that time, no battery up to 7.2 V. Then, it
> will sit until I try again. I can slowly discharge them as well and cycle
> them a few times if that is the best way. Should I cycle them under heavy
> EV load or use something like a 100 W bulb, which will be very very slow?
>
> Steve
>
>
>
>
> _______________________________________________
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________