Re: [EVDL] How much does OCV 1 hr after charge and voltage at fullcharge change for o

Re: [EVDL] How much does OCV 1 hr after charge and voltage at fullcharge change for o

Steve,

These are *flooded* batteries, so they must be *vigorously* gassed
for some time to stir up the settled electrolyte to "wake them up"
after sitting for so long.
Also the gassing of one battery or one cell allows the next one to
continue charging until *all* are full (top balance) so you should
continue to charge until you have calculated that all should be full
or when you can see every cell gassing vigorously.
No problem if they will climb to 2.5V per cell, but if they are warm
then they may never get there. In fact, you may see the voltage start
to drop towards the end from the batteries getting warmer and the
charge voltage slowly dropping as a result.
once they are fully charged, you may want to top them off to make sure
that none are dry (you must not be able to see the plates, usually
there is a marking on the battery or the fill opening how high the
fluid level should be. Not too high because then they will vent
vapor and mist much too easily and you will need to clean them often.


Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Steve Powers
Sent: Monday, September 27, 2010 3:51 AM
To: ev
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




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