Triple battery setup - any ideas?

That sounds a similar set up to mine but in my case I have a 175a Anderson plug and 18mm2 cable from my primary battery (through a soliniod) to my seconadary battery on the drawbar of my caravan. I also have a thermal overload in the circuit as well as a fuse

Interesting, I'm looking at doing the same thing. One aux in the engine bay, two on the camper trailer. Have one of the trailer batteries at the moment, a 120AH AGM. I've been told that all the aux batteries need to be the same type and near the same age to ensure they all charge fully. I would therefor need all aux to be AGM. Fatz, I see you have a mixture of batteries. Any problems?

Are your 3 batteries on the trailer connected in parallel? When they charge from your alternator are these three in parallel to your vehicle aux at any time?

I was looking at a Rotronics 3ST12CF (don't know what they cost, have only read about them). I believe it would work like this:
After charging the cranking battery, it will charge the trailer batteries (if connected). when they are charged, it connects the vehicle aux in parallel. This results in the vehicle aux fully charging and the trailer batteries charging to 80 to 90%. I think they get pulled down by the vehicle aux when it is connected. I have no experience, but this is as I understand the recommended way to run this system.

Don't mean to hijack your thread fatz, but since our issues are similar, I thought we could learn together.

Thanks Undertaker, tried the archives but could not figure out what I wanted to know. what model rotronics unit are you useing?

Mick

Melissa,
this sounds like exactley what I'm after. may i ask what sort/make of solonid you are useing?

Mick

Mick, I just had a look at the solenoid. It's an AED 12V 081-16-013. I don't think it's anything fancy, just an ordinary 12V jobby. Only thing unusual about is that we got the auto sparky to put a 10 cent doide across the terminals which we were told would absorb any spikes. This advice came from Collyn Rivers electronics wizz and author of several books on solar power and electrics for caravans, motohomes and RV'.

:o) Melissa

Melisse, thanks for that, really appreicated.

Mick

Glad to have been of assistance. We're on our 4th 4WD. All have had dual battery systems. First one was a manual set-up using a marine switch to direct charge to battery of our choice. All the others have been solenoid set-ups and we've never had a problem with any. Funny thing though is how easy it is to get bogged down with all the choices and fancy "must have" systems that are around these days. With the Nissan we put off installing a DBS for months because we got so confused with all the conflicting advice and opinions. In the end we thought this is ridiculous - go with what we know and what in our experience has always worked well. Also, I agree with your auto elec - KISS principle!

:o) Melissa