Unstable SLA Voltage or Faulty DMM

[metrologist]

I have 3 SLA batteries that probably came out of UPS. Last year I had them connected to a solar panel for most of the summer to try and revive them - I think one or two were still OK volts when I got them, and one was down to 10.5. I let them sit on the shelf over winter and measured the voltages this morning. All three were bouncing around between 12.5V and 14V. That has to be a faulty DMM, right? It's the free harbor freight model.

[thm_w]

Your name is metrologist and you don't have a suitable DMM to measure with? 

You could try placing a small load on it and see if it will stabilize on a number.
I've seen odd voltages with SLA, but should never bounce with a static load afaik. So most likely meter is not reliable.

[metrologist]

Well, I was out in the garage on my way to out to work. I'll verify again, but just the very idea that it could be the battery was a bit perplexing, and all three? I'd never seen that, and if it is the meter, that might be something of interest.

BTW, I have kind of a split personality. Sometimes I go by Metrolojest. 

[metrologist]

Well, when I got home I measured again. stable 12.48, 12.46, and 12.25, just toggle the last digit ever so often. I had a second cheapo meter that verified within 20mV. 

[Gyro]

It sounds as if you need to clean and/or check for continuity of your test leads (check they don't go o/c with a little tension on them). Either that or plug them in fully! 

[metrologist]

Might also be a weak DMM battery. Those leads though... I just wanted a sanity check that SLA batteries could not exhibit that phenomena, or it would be extremely rare. I guess anything could be happening with aged batteries.