# Hook up 240V does not charge vehicle battery



## wakeman (Nov 23, 2009)

Hi sorry if this is a basic question but I am new to MH. I have some knowledge of auto electrics ( but this could be dangerous!!!) Having just suffered a flat main battery despite the fact that it was on 240V hook up all the time. I requested the circuit diagram from Hymer for my 1991 Hymer B644 which they kindly sent me. However on tracing out the circuit I realised that the on board 240V to 12V charger does not charge the vehicle battery, why is this.


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## Jennifer (Mar 24, 2009)

This has always been my understanding, but I do not know the answer, and would, like you, be interested in knowing.

Jenny


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## CliveMott (Mar 10, 2008)

The inbuilt charger is primarily designed to charge the leisure battery. Up to recent years this is all it ever did. Its only relatively recently that some electrical systems provide a small charge to the starter battery as well as the main charge to the leisure battery.

But why was your starter battery depleated? Did you leave something in the cab switched ON or perhaps its the radio or alarm system?

There are a couple of different add on ways to allow the inbuilt charger to charge the starter battery.
1) The BATTERY MASTER (or is it battery mate?) is a small encapsulated block that will charge up to 1 amp into the starter battery once the leisure battery is up to its float charge voltage.
2) The simple method, a fused link. See here. http://www.motts.org/BRIDGING FUSE.htm

C.


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## Chudders (Jul 5, 2008)

I had a battery master fitted to my van at Vanbitz and worked well. I,ve now bought another vehicle so I removed it ready to install on my latest motorhome.
Dave


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## wakeman (Nov 23, 2009)

Hi Clive, 

thanks for the quick reply, you are dead right I was doing a couple of jobs inside and had the radio on, unfortunatly I had left the radio on standbye which was enough to disscharge the main battery after a couple of weeks.

I will try and source a battery master for peace of mind


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