Another victim made it's way into my collection the other day, and so far I've seen good results.
The basic background is something like this:
12V 5AH SLA, removed from a small UPS, brand new in the box (still had prong protectors on the cord), and was returned because 'it didn't work'.
A friend of mine passed it along to me, and it sat in my car for a couple of months before I got to it. Nice hot, unforgiving trunk, going everywhere I went and then some for I don't even know how many miles, bumps and all.
Popped the UPS out of the box the other day, plugged it in, and sure enough, zip. zero. nada.
No surprise, went for the best guessed culprit. Again, sure enough, 1.4V or so at the terminals. Very nice. A star was born.
I pulled it out, let it sit for about 12 hours to let it cool off (was still rather warm from the trunk), and then laid a 2mA (no typo) charge across it (intentionally current limited to this level) and left it to sit for about 4 hours. After this, it measured about 10.5V.
Ok, time to up the current a bit. Set it up so that when it hits 12.0, it would be drawing 50mA, the C/100 rate. It was nowhere near that when charging was first resumed. Started out just shy of 10mA. After 9 hours or so, it was drawing 35mA (ish) and appeared to still be climbing. At 12 hours, it topped out just shy of the 50mA limit. Measured terminal voltage was about 12.1V.
I let it sit for another 12 hours like this, came back and the current was down a bit, around 40mA. CTV of 12.3V or so.
Ok, lets see if she'll bite.
She did. Upped the current to 100mA, took it instantly (without that recovery 'climb'), and has dropped only to 95mA or so over the course of the last 6 hours. Terminal voltage at last check was 12.4V.
Time will tell, but the math (AH accumulation) points me to about the 20% charge range at this point. Took it a while to get going, so the math probably isn't hardcore-accurate, but gives me an idea.
CTV tells a slightly different story, I'm thinking somewhere in the 35 to 40% range. If I'm right, it will have a recovered capacity of about 2.5AH at the 20 hour rate when it's all said and done.
Stay tuned, I'll inform.
No other special treatment was done. Just a really S L O W charge rate.
Steve