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Electrical problems

Our boat has a Victron inverter/charger and a dedicated alternator to support charging and 240 volt ac power.It also has a battery management system. All worked well at first, but now, after two seasons relatively low use, the batteries lose charge overnight to a point where the low level warning is flashing and 240 volt power fails in the morning without running the engine. We are sure we are neither using any additional electrical items nor using them for any longer than before this began to happen. The batteries have been bench tested and have been shown to be in good order. Can you suggest what else might be causing the problem? What further checks can we make to identify it and hopefully find a solution.

Asked by: Richard Holland  | 10.49am, Friday 4 March

WW says:

I think you may have sulphated you batteries, but you might need to email me at mark.langley@waterwaysworld.com if you want to discuss it further.
Although you have had them bench tested, if they are wet open cells it is worth doing the following:
Top them up and charge them, leaving them to stand for 24 hours and then compare Sp. Gr. hydrometer readings with the voltage. I suspect you will find the voltage is showing charged but the Sp.Gr. shows less charged because the sulphur from the acid is locked up in the sulphation. If you finds the voltage has dropped you will know you have a faulty battery. You can take one battery out of your bank at a time to do the test.
Let us know if that helps.

Mark Langley  | 4.35PM, Saturday 12 March

Readers say:

Turn your fridge off, buy new batteries.

Workboat Pug  | 6.51PM, Friday 11 March

Thank you for your suggestions, though the tests suggest that the batteries are OK. Also the fridge has always been left on overnight and I have assumed because the problem is recent that that was not a cause for concern.
I have been persuaded to try switching off each circuit in turn overnight to try to identify the one reponsible. I will start with the fridge!

Richard Holland  | 9.55AM, Saturday 12 March

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