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Battery maths don't add up!

I have been monitoring my battery voltage levels recently and the battery voltage level seems to be far lower than what I would expect.
If I charge the batteries fully from a mains three step charger and disconnect this and leave them overnight the voltage has dropped to about 12V.
I have calculated the load to be about 50Ah overnight and the batteries are three 110Ah lead acid sealed leisure connected in parallel and are about 3 months old.
To me the voltage should not be dropping that low. I have noticed the main battery lead is connected to just the first battery and the other two are connected in parallel to this. Could this be a problem or is it possible I already have a dead battery?

Asked by: Adam Savory  | 9.23am, Wednesday 28 October

WW says:

Presumably you have been monitoring the voltage because the batteries are not performing as well as expected. If however this is not the case and there has been a recent drop in voltage, the drop is probably due to the weather. Temperature affects chemical reactions, and in this case the voltage will drop with the cold weather; this will be particularly noticeable if the batteries are outside under a cruiser deck. The difference between similar measurements made in summer and winter can be up to 0.5V.
The alternative is that one of the batteries is failing; removing the interconnecting straps, measuring the voltages and leaving them overnight or longer will identify if one is dropping significantly.
Staggering the positive and negative connections across the batteries will help even out the load, but is not the problem.

Rupert Smedley  | 10.11PM, Tuesday 3 November

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