Leon Keefer avatar image
Leon Keefer asked

2V Battery Damage

bess.pngRunning 24V system with 12x 2V 1500ah Mastervolt traction gel batteries, all on their side. Batteries are connected via connector plates Inherited this ESS, it's located under the house on clay soil and some structural plywood. 100kg each, not surprisingly the ground has settled a bit over the last two years and the top two middle batteries have slid back. The terminal connection held strong and the plate/terminals have been pulled out a couple of centimeters.

Voltage on the other 10 are all reading fine and balanced, but the two damaged ones were less than 1V each. They've obviously discharged but haven't been able to charge up to the same level as the rest of the system. Now the system sits at about 26V with the sun on and balances out at about 20.5V. I've disconnected the two damaged batteries and there is no difference in the performance of the system.

The question: best way to fix? Seems like battery balancers (active) would take too long and likely mess the other batteries up. My current plan is to run a 20V system until the working 10 discharge down, reconnect damaged batteries and charge up, disconnect damage batteries and discharge the 10, on and on until the 2 damaged ones are back at an acceptable level.

Another idea was to try and trickle charge the 2 batteries separate to the rest of the system, but nothing in the market to charge 2V or 4V systems, and I'm worried that hooking up to a trickle charge solar panel would be more trouble than it's worth? Not going to move them out (it's very, very hard and inaccessible) but could get some looong wires from a small panel. Would monitor this rather than using an MPP controller.

Anybody with experience on this one?

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1 Answer
snoobler avatar image
snoobler answered ·

It's almost an impossibility the cells are salvageable.

  1. They've sustained physical damage
  2. They've sat in a deeply discharged state for an extended period.

#2 in particular essentially ensures that they are a total loss.

I assume you've reconfigured the charging for the reduced cell count. If you haven't, you are destroying the cells. GEL batteries must not be charged to higher voltage.

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Leon Keefer avatar image Leon Keefer commented ·
Thanks for your thoughts. I’m hopeful that the damage isn’ttoo bad and that the length of time in a discharged state wasn’t too long. They were always connected to the bank and topped up with a generator. After 24 hours of them being disconnected, one read 1.1v and the other only 0.24v. Lucky to have a sunny day so I hooked them back up and after a decent amount of sun, I unhooked them again to let them keep charge overnight. They’re sitting at 1.9v, but I’ll see what they read after a few hours off line.

Fingers crossed.

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snoobler avatar image snoobler Leon Keefer commented ·
You're taking hits off the hope-ium pipe. I don't think you understand how fatal deep discharges are to lead acid.

1.1V is a dead battery.

0.24V is already rotting in hell.

1.9V after charging overnight = dead

If you were certain these batteries were perfectly operational a few days ago, I might agree with the potential that they can be salvaged, but I get the impression that it could have happened weeks/months ago.

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