Budget battery to battery charging

[Noctule]

Hi all,

Given that a good quality B2B charger is still quite a pricey proposition for those of us touring on a budget I'm considering an alternative and wondered if anyone else has tried the same...

As I've already got a couple of inverters and a Numax 10a fit-and-forget charger I'm thinking about hardwiring them into the camper to create a B2B system which is 12v-240v-12v. I'm assuming that it will take a bit more power than say a Sterling, but the charging benefit will more than outweigh that. What worries at the moment is that the Numax charger is a item that should be earthed.

Has anyone tried the same or have an opinion on the electrical safety of such a system?

Cheers,

Mat

[hectors-tranny]

I wouldn't. But aside from the obvious safety issue of having no earth for the 240V charger, that system still doesn't provide a split charge facility. I.e. when the engine is off, the inverter would still draw current from your starter battery.

If you really can't afford a B2b (and I would thoroughly recommend them), your best bet would be a direct positive to positive connection between batteries (correctly fused of course) with an isolator switch to manually disconnect the starter batter when necessary. (Or a VSR)

[CasualNerd]

VSR's are relatively cheap and perfect for the job.

I spent a bit extra on a Victron 'smart' VSR but it can work both ways in the event your main battery needs a boost for starting etc.

[Noctule]

I've already got a VSR, and that in turn switches larger relays for battery charging, fridge, etc, but even then it means the leisure battery is charging is only at around 14v at best once everything else is up and running and I've been driving for a good few hours. I think I'll look at larger cabling first, just to get the best out of what is available.