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Daft question from a newbie regarding batteries!!


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Hi Guys...

Due to buy our first motorhome soon and cant wait!! Anyhow a quick question regarding batteries and charging.

Does the leisure battery charge up once the engine battery is fully charged whilst the engine is running? Also does the mains hook up charge both batteries, just the leisure or neither (?) .

The main contender for us at the moment is a sunlight A63 2008 model on a transit chassis.



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Need to no what charger unit fitted. I do not have a Deff and somebody will come along to help you.


How it work in my MH is the engine will charge both the starter and leisure batteries, however once the engine battery is charged the output from the generator is reduced so the leisure battery may not get a full charge.


On hook-up I can choose which battery to charge from the control panel and it is normally the leisure battery. I have on the odd occasion discharged the engine battery and have used this charger to get sufficient in to start engine.


Hope this helps and enjoy your MH

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Hi Ryan

Before going on any trip, plug into the mains preferably the night before with the fridge on mains. Ideally with some items already cold from your household fridge. Your on board charger will fully charge your leisure battery and your vehicle battery. While driving the alternator will charge both and at a very high output. When on-site and you plug into the mains again both will be charged.

If your not using the mains the Mh will take from the leisure battery, so you can still start your engine. Enjoy !!!!!!!



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The Leisure battery is charged from the alternator or when on mains hook up.

Some Motorhomes have a system fitted which allows charging of both when on electrical hook up so you do need to consult the instructions/specs for the system fitted. When on Mains hook up the engine battery is usually just a trickle charge if the option exists.


To clarify charging of leisure battery from alternator, in effect both batteries are joined together when the engine runs by what is called a split charge relay. What happens is both batteries charge. The alternator generates 14.4 volts so both batteries charge up untill fully charged and the alternator does not cut back as such, each battery will take what it needs. There is no priority over which battery charges 1st. They charge together.


edit - typos

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Welcome to the Forum Ryan - and it's not a daft question at all - in fact it's a very sensible question! We all had to learn - most of us the hard way!


Following on from Brambles posting, do note that whilst the alternator will charge the engine battery very quickly, the current to the leisure battery(ies) is restricted to about 10 amps and it will take a lot of miles to replenish two 110 ah leisure batteries that are well down.


It's not a problem when you know what to expect and there are ways round it but they are expensive - and if you only ever stay on sites and use ehu it's not a problem at all!

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