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Battery Discharge

My Starter Battery [In excellent order], charges nicely when my Barrus Shire engine is running, but discharges overnight. Advice please!

Asked by: Michael Clement  | 3.31pm, Thursday 7 September


WW says:

A difficult question to answer without some more information.....
Is there a dedicated alternator for that battery or do you have a split charge system?
Is there anything else connected to the Start battery such as a bilge pump/solar power etc?
Does it still do it if you turn off the Start battery isolator?

Rupert Smedley  | 4.56PM, Thursday 7 September

In my (bitter) experience, starter batteries can appear perfectly healthy yet be at death's door. On one occasion, I had the starter motor serviced only to find that the problem was the battery. It seemed to be as normal but, when the starter motor was engaged, the voltage in the battery dropped to zero. New battery - problem solved.

Graham Booth  | 8.59AM, Friday 8 September

Graham has a good point: how old is the battery?

Rupert Smedley  | 9.18AM, Friday 8 September

Are there any other circuits connected to the engine battery and is the alternator isolated by the battery isolator?

Rupert Smedley  | 11.22AM, Monday 11 September

I would try charging the battery and leaving it disconnected overnight- and then see if charge is being held (its just possible that the new battery happens to be faulty, but fairly easy to eliminate).
I do wonder if, somehow, the alternator is effectively being energised somehow; as Rupert suggests, check all the connections that are linked into the battery- and that the isolator actually works (I have seen isolators where both connections were made to a single stud!)

Mark Langley  | 1.50PM, Monday 11 September


Readers say:

2nd New Battery that I have tried- approx. 1 Day old!. Strictly for starter only with dedicated engine alternator. Still does it with Battery Isolator off! Electrician has scratch marks on his head!

Michael Clement  | 3.16PM, Friday 8 September

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