12v / Mains auto switch

[tommy3000]

Hey, I am just starting out converting one of my vans (VW Crafter) into a camper. At the moment I'm in the planning stages of my conversion and hoping to start early Jan.

I am hoping to get a little advise on split charge systems.

I will have two leisure batteries (around 100ah each however ah isn't 100% yet) which I would like charged from the starter battery whilst engine is running but auto switch off / or over to the mains system when hooked up to mains.

What system would you recommend for this?

Thanks is advanced

Tommy

 

[rosalan]

A solar panel and one of Eddie VanBitz battery master units

 

[HandyAndy]

MultiPlus 500VA - 1600VA - Victron Energy

The MultiPlus 500VA - 1600VA is a powerful true sine wave inverter, a sophisticated battery charger and a high-speed AC transfer switch in a single compact enclosure.

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[Stealaway]

I will have two leisure batteries (around 100ah each however ah isn't 100% yet) which I would like charged from the starter battery whilst engine is running but auto switch off / or over to the mains system when hooked up to mains.

Sterling B to B ?

https://cdn.shopify.com/s/files/1/0658/7343/files/2019_GREEN_V69_Rev_Instructions.pdf?92

 

[autorouter]

A minimalist solution is just a standard split charge relay setup, which will do what you require. It is a relay controlled by the D+ wire from the alternator, which is ON when the engine is running, and goes OFF when it stops. The relay connects the starter and leisure batteries while the D+ wire is ON.

A smart mains charger can be permanently connected to the leisure batteries. There are 'diodes' in the charger that prevent any backflow of current into the charger, even if something else is charging them.

It's best to use the D+ wire rather than an ignition-controlled feed. The D+ doesn't come on until the engine has started, and the starter motor has finished starting the engine. You want to avoid connecting the starter and leisure batteries together while the starter motor is running, it takes a huge current.

A better solution between the starter and leisure batteries is a Battery-to-Battery (B2B) charger, which takes power from the alternator and boosts it to give the leisure batteries a proper high-current charge, to get them back up to 100% much quicker than the alternator will ever do. Using a B2B means a split charge relay is no longer required.

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[addoaddo]

It does depend on if you have a "smart" alternator which are fitted to newer vans. These drastically reduce the power generated when it is not needed. If this is the case you will need a B2B as this "foils" the alternator into thinking that it need to produce more power.
The split charge route is by far the cheapest but a B2B will charge your leisure batteries much faster and more importantly not over charge them