I was given six Trojan J305P (very close to an L16 in size and specs) batteries today. Cool! Of course, TANSTAAFL applies - these things came out of a floor polisher that, as best anyone can remember, sat unused (and uncharged) for over 5 years! One of the maintenance guys at the plant pulled them and checked them out. They needed a LOT of water, and surprisingly did take some sort of charge. Then they figured out they'd never fit the things into the golf cart they wanted to refurb, so set them aside and forgot about them until I showed up. They know I piddle with solar power, so the offer.
Can't beat free, so I figure even though they are likely junk they will at least give me cores (or salvage value?) in case I want to buy something else.
However, I thought I'd play with them a bit, see what (if anything) they can do. Might as well have a little fun, and maybe learn something in the process! I do have a few questions about that though, as I've never worked with old batteries before.
Primarily, what would be the best charge / discharge rates? Whatever I can manage? High? Low? Not sure whether to be gentle while they are weak or just kick 'em hard and see if they can handle it!
For charging, I can supply anything from 750mA to 55A. If the sun would ever show up again, I may also try connecting a set to my 12V panels. (It's been nothing but overcast and severe storms all week!)
I'm going to be working with these in 12V banks (two in series) - four of them are usable, two have decent SG and actually pretty close to each other, the next two are a little farther off but still serviceable. Those four were holding at 6.1V today, after sitting on the dock for a week or two untouched. I probably will need to equalize them at some point - the SG readings are somewhat out of balance.
The last two intrigue me - hopefully someone can perhaps explain this. Their resting voltage was 4V. When I checked the SG, one cell in each measured 1.0! Plain water?!? The guy who worked on them did say he had to add a lot of water to some cells, but the cases aren't cracked and the batteries hadn't been spilled - so what happened? Is it actually possible for enough of the electrolyte to react with the plates that you'd read 1.0? The maintenance guy did try charging them, not sure for how long. Anyway, I'm figuring those two aren't worth messing with at all, unless someone suggests otherwise!
SG readings I measured after carting them home and before charging:
1) 1.225 / 1.150 / 1.225
2) 1.150 / 1.150 / 1.225
3) 1.225 / 1.225 / 1.230
4) 1.160 / 1.225 / 1.225
I've paired 1&2, and 3&4.
The "dead" two:
5) 1.000 / 1.100 / 1.240
6) 1.200 / 1.000 / 1.175
All thoughts and suggestions are welcome!