Damaged batteries

[monzer]

I got a low battery warning a couple of weekends ago. It had been a dull weekend for solar and I'd the heating on a fair bit but even so I was a bit surprised at the warning.

Had a look through the victron smart app history and noticed 2 low voltage warnings and 1 high one...

I think this coincides with when I found a loose connection at the fuse coming from solar mppt. But would that cause the low/high battery? I've not been off hook up long enough for anything to take the battery that low.

Today I switched off the mains and watched the battery voltage drop from about 13.4 to 12.5 with a draw of TV and heating (about 3.5a) in around 5 minutes.

Are my batteries damaged from whatever caused the drop to 10.45v?

2 victron 90Ah gel batteries in parallel.

 

[Richard n Ann]

I got a low battery warning a couple of weekends ago. It had been a dull weekend for solar and I'd the heating on a fair bit but even so I was a bit surprised at the warning.

Had a look through the victron smart app history and noticed 2 low voltage warnings and 1 high one...

View attachment 693809

I think this coincides with when I found a loose connection at the fuse coming from solar mppt. But would that cause the low/high battery? I've not been off hook up long enough for anything to take the battery that low.

Today I switched off the mains and watched the battery voltage drop from about 13.4 to 12.5 with a draw of TV and heating (about 3.5a) in around 5 minutes.

Are my batteries damaged from whatever caused the drop to 10.45v?

2 victron 90Ah gel batteries in parallel.

You'll need to watch them longer to see if they are kaput.

 

[Lenny HB]

If the 10.45v was under load they will survive that, if it was off load not so good.
The 13.4v was because they have just come off charge Gels tend to hold a higher voltage for longer when they come off charge, if you left them for 24 hours they would drop to around 12.9v.
Bearing in mind 12.7v off load is considered to be fully charged a drop to 12.5v under load is quite normal.

 

[monzer]

Thanks Lenny. Is the drop to 12.5v under load normal even when it happens that quick? It was literally no longer tha 5 mins after I unhooked power.

How can I test them?

 

[Lenny HB]

Thanks Lenny. Is the drop to 12.5v under load normal even when it happens that quick? It was literally no longer tha 5 mins after I unhooked power.

How can I test them?

Yes quite normal, best way to test is on a slow discharge and test each battery separately.

First charge the battery fully and leave it to settle for an hour then:-

For example if it's a 100a/h battery load it with a 5 amp load and run for 5 hours, this will represent a 25% discharge. (adjust load/time to suit the size of the battery)
Disconnect the load and leave to stand for at least 30 min then measure the voltage.
Repeat the test and you will have discharged the battery to 50%.
You can repeat again then it will be 75% discharged.

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