trickle charging starter battery & PSU modification

[t0mb0]

Hi Guys, I've just bought one of the Votronic trickle chargers to keep my starter battery topped up from the leisure battery, with the leisure battery being topped up from a solar panel on the roof. Before I install it I'd like to know what stops the starter battery draining the leisure battery if the van is parked indoors with no sunlight? Wouldn't the starter battery become a parasitic drain on the leisure battery? Thanks.

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It needs a 0.5v (or something like that) differential for current to flow so it's not going to flatten your leisure battery. It's a simple device, but it's basically foolproof, just install it and it'll keep your starter topped up with zero fuss or configuration. We have one (although in our case it's built in to the solar controller) and it just works, I haven't had to even think about my starter battery since I installed it.

The only caveat to this is if you're running a lithium leisure battery, it's not suitable for this and you'll need a more advanced/expensive gizmo like the one @Dellmassive posted above.

 

[Grantls]

Thanks for the replies. So the resistor prevents current flow until a 0.5v differential between the two batteries is detected? Simple but effective.

 

[Dilbert]

A diode needs 0.5 to 0.7V voltage difference (depending on type) to start conducting. The resistor limits the amount of current. A thermal device may be fitted to prevent overheating if current too high.

Simple, affective but the Votronic device is expensive for what it is!