As part of my upgrades to get ready for the PV, I was moving my inverter and battery bank to the new attached garage.
All was going as expected, until I got to the very rear most bank of 4.
None of my connections had corrosion.... but one.. And of course I did not get images of that.
Worse, it was so bad it had completely disconnected that bank, and its been this way for at least 4 months through the worst of Minnesota winter.
The batteries appear to have frozen, they are bulging, and the one has a post raised.. Not good.
I tested voltages, and the surprising part was that they had anyhting, let alone all within about .02v of each other.
Bad part was, they only had ~5.96v
So they were topped off with distilled water, and individually connected to a 6v charger.
Each would draw approx 12 amps individually, so I banked them in 2x series and parallel to charge at 12v overnight.
Today sometime I will setup the charger to equalize and see how things go after that.
They are 9 years old now I guess, so it could be worse. I got them less than a month after they were shipped from the manufacturer.
Sorry for te poor images, this is the best I could get at night in a snow storm