# Leisure Battery Wiring



## Tom2023

I am trying to sort out the battery power in my Motorhome. I don’t have a circuit diagram and the wiring is a bit of a Rat’s Nest and it disappears into the bodywork just as it gets interesting.

This is how I think it works…

When the Engine is running the Engine battery and the Leisure battery are charged in parallel by the alternator.

When the ignition is turned off the Engine battery is then isolated from the Leisure battery so it is not drained while watching TV?

When the ignition is turned on then the Van is then isolated from the Leisure battery. The Leisure battery & Engine battery are then back in parallel and the Leisure battery is charged up from the alternator.

I think that’s how it works but if it does then wouldn’t a flat Leisure battery be a drain on the Engine battery when it’s trying to turn the engine over?

Is this right or is it more sophisticated?


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## lenny

Hi. Tom ,Try this link, it seems to explain the whole system of split charging.

http://www.kampenwagen.co.uk/Split Charge.htm

Good Luck


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## Belgian

Tom2023 said:


> I am trying to sort out the battery power in my Motorhome. I don’t have a circuit diagram and the wiring is a bit of a Rat’s Nest and it disappears into the bodywork just as it gets interesting.
> 
> This is how I think it works…
> 
> When the Engine is running the Engine battery and the Leisure battery are charged in parallel by the alternator.
> 
> When the ignition is turned off the Engine battery is then isolated from the Leisure battery so it is not drained while watching TV?
> 
> When the ignition is turned on then the Van is then isolated from the Leisure battery. The Leisure battery & Engine battery are then back in parallel and the Leisure battery is charged up from the alternator.
> 
> I think that’s how it works but if it does then wouldn’t a flat Leisure battery be a drain on the Engine battery when it’s trying to turn the engine over?
> 
> Is this right or is it more sophisticated?


That's right, you got it.
There should be a relay (or a one-way-diode) between your engine and leisure battery. It it allways goes one way: charging 1 engine batt and 2nd leisure. Therefore a flat  leisure cannot drain off the engine battery. When you hook up; you only charge the leisure (normally). The 2 are working indepentent; when you charge your engine battery externally your leisure is also charged when the engine is full. Not too confusing ??


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## wildman

correct but only if the ignition is switched on to energise the relay.
Confusing ain't it.
Roger.


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## Belgian

wildman said:


> correct but only if the ignition is switched on to energise the relay.
> Confusing ain't it.
> Roger.


Right. When you have ignition the relay is on: engine + leisure batteries are charged. First the engine battery and then the surplus to the leisure. It goes off when you pull the key out; so no current engine battery> leisure. You only drain your leisure battery when you watch tele, and never the engine. 
For the same reason when you hook up (240V >12V) you are only charging your leisure bat. and not the engine one.
The next invention will be matches and a candle


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## guerdeval

Just a mention there is a small thingy that will trickle charge your truck battery when plugged into 230v after the leisure battery is full, useful if you don't plan to drive for a while, no idea what its called but Vanbitz sell them, (sorry 'm not technical)


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