One 12v battery suddenly reads negative in 24v series bank

Cascadie

New Member
Joined
Feb 7, 2021
Messages
2
Hello all,

I've been lurking and learning here for a while but now I have an issue that's got me concerned.

As per the title, one of my 2 AmpereTime 12v 200ah batteries reads -0.01v when isolated. This happened while there was no charging going on. (7am) I let it rest a bit thinking the BMS shut it down; the manual said it should reset in half-hour, but it did not. I hooked up the batteries in series again and put them back on the charger and it does take a charge just fine.

This is the second time this has happened. The system has been trouble-free for 4 months, but it went kaput one night when wifey put the electric kettle on. (500w load on a 3000w 24v Girandel inverter). The system was over 25v at the time. We left it disconnected overnight and it was okay in the morning.

This last time (same battery, same symptoms), there was very little load, and still above 25v when we went to bed, and could possibly have seen a load of less than 8amps at the time the battery went down again. The temperature was in the 40s F this time, a tad under 40F last time.

One thing that may be an issue. I only charge these with the solar charger (Victron Smart Solar 100 | 30). When they are charged, they are within a few tenths of a volt of each other.

I will provide details on the system if needed, but would cause one battery of the system to suddenly shut down like that?

TIA
 

Cascadie

New Member
Joined
Feb 7, 2021
Messages
2
I guess my learning needs to continue... I had assumed I had quite a bit higher percentage of battery storage at 25.6V than 10%! It sounds like my BMS is just shutting down when it really should be!
 
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