this post was submitted on 29 Sep 2023
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Two battery setup in camper (lemmy.world)
submitted 1 year ago by figurys@lemmy.world to c/askelectronics@discuss.tchncs.de
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I want to change te battery setup in the camper van a bit.

Currently there is a single battery which is charged by either solar, engine or 230v. Then a transformer to 230v to power the outlets.

The idea is to add an extra battery. A lot of people are saying that it isn't a good idea to put those batteries in series or parallel if the batteries are not exactly he same. Now our idea is to switch between the two batteries with the help of some relais and an Arduino or something. So then + of both batteries would be connected to a relay and after the relay we can connect them together. Is this a good/safe way of doing that? Or will we be running into issues that I'm not seeing.

Thanks in advance!

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[–] IsoKiero@sopuli.xyz 2 points 1 year ago (1 children)

So you'll have total of 3 batteries at the car? One for engine, existing utility battery and now you're planning to install another utility battery, right? That should work. I don't know how much current you're pulling from the battery, so it's difficult to recommend anything. Common bosh switching relay is something you can find from pretty much every car part store for ~5€, but I think they're rated only up to 40A and I wouldn't push them to the limit. Check your inverter datasheet how much current it can draw and preferably get a relay which can do double the maximum rating for longevity and stability.

[–] figurys@lemmy.world 2 points 1 year ago

That is correct. 1 battery for the engine and 2 for utility. I guess it has to be quite a beefy one. The interter is rated for max 166 amps. So that's quite a bit. Which also makes it a bit hard to find a suitable relay.