Triple battery setup - any ideas?

Submitted: Thursday, Apr 21, 2005 at 18:15
ThreadID: 22264 Views:9731 Replies:5 FollowUps:7
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I'm looking at putting a third battery in the camper trailer. Already have two in the 4x4. Dont currently have any switching mechanism fitted. What I would like to do is have a main starting battery, an auxillary in the 4by and an auxillary in the trailer. I would like to run the fridge and a couple of lights for a couple of days/nights off the trailer and if need be plug in the auxillary from the car to run the trailer at night when you use the most power. we spend most days out driving so recharging the auxillary in the car shouldnt be an issue. I run a winch in the car off the cranking battery and will be getting a small fridge at a later date.
Anyone got any suggestions for a good switching mechanism that could be put together or an off the shelf one that doesent cost you your first born?
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Reply By: Member- Rox (WA) - Thursday, Apr 21, 2005 at 18:36

Thursday, Apr 21, 2005 at 18:36
Yep just spoken to an auto elec as my 2nd batt died. Ive got a solinoid but there are now some electric thino's that charge the starter first the when the volts are ok switch over to acc. I also have a 3rd in camper MUST have a fuse in line incase you get a breakage I'd sugest 2 fuses 1 @ each end(near Batt car & batt camper) Ive got nothing fancy except a 50Amp anderson plug on rear bumper and runing through a frame to stop stone damage all 3 conected when running. If you don't know what an anderson plug is search the archives as there was a pic some months back. Ps I get 2 days out of a 100amp Deep cycle with 2 x 1amp fluros + 40lt engle but do recharge every day.
AnswerID: 107706

Follow Up By: Ray Bates - Thursday, Apr 21, 2005 at 20:47

Thursday, Apr 21, 2005 at 20:47
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
FollowupID: 364615

Reply By: TheUndertaker - Thursday, Apr 21, 2005 at 19:31

Thursday, Apr 21, 2005 at 19:31
fatz, can only say check the archives , I run 5 batts all thru a Rotronics sysrem [ no not the expensive c/van jobby, mine is only $240]
no 1 = start bat =h/d 900cca
no 2 = aux bat = 70 amp hr Delcor low maint marine [not deep cycle]
batts 3/4/5 = 80 amp ea AGM for total 240 amp/hr on c/trailer .

start bat to aux thru Rotronics ,aux to c/t x3 AGM thru min 8mmsq cable + anderson plugs ,,, ,,,,,,works for me ,,,have zip voltage loss and ALL batts fully charge.
AnswerID: 107710

Follow Up By: normc - Thursday, Apr 21, 2005 at 20:39

Thursday, Apr 21, 2005 at 20:39
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.
FollowupID: 364613

Follow Up By: fatz - Thursday, Apr 21, 2005 at 22:22

Thursday, Apr 21, 2005 at 22:22
Thanks Undertaker, tried the archives but could not figure out what I wanted to know. what model rotronics unit are you useing?

FollowupID: 364622

Reply By: TheUndertaker - Thursday, Apr 21, 2005 at 21:06

Thursday, Apr 21, 2005 at 21:06
Normc + fatz ,, all I know is that my system works for "me" ,,, AGM batts are no where near as difficult to live with and fully utilize as deep cycle ,,, no need for a 3 stage charger ect,,can be run down to 35/30% without doing FATAL damage ,,, self discharge of less than 1% per mth ,,, pump in as many amps as you are able at 14.2 volts and the AGM laps it up ,,,,,,Rotronics + AGMs is the "perfect" match,, bit like Fred Astaire and Ginger Rogers ,,,LOL.
AnswerID: 107723

Reply By: Member - Melissa - Thursday, Apr 21, 2005 at 21:12

Thursday, Apr 21, 2005 at 21:12

We're running 3 batteries - main, car aux and trailer aux. Basically we've just a solenoid to isolate the main battery when the car is off, otherwise all three batteries are charging in parallel. Trailer battery is connected via an anderson plug. System works well for us - no complaints.

:o) Melissa
AnswerID: 107724

Follow Up By: fatz - Thursday, Apr 21, 2005 at 22:19

Thursday, Apr 21, 2005 at 22:19
this sounds like exactley what I'm after. may i ask what sort/make of solonid you are useing?

FollowupID: 364621

Follow Up By: Member - Melissa - Thursday, Apr 21, 2005 at 22:35

Thursday, Apr 21, 2005 at 22:35
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
FollowupID: 364624

Follow Up By: fatz - Thursday, Apr 21, 2005 at 22:42

Thursday, Apr 21, 2005 at 22:42
Melisse, thanks for that, really appreicated.

FollowupID: 364626

Reply By: normc - Friday, Apr 22, 2005 at 20:35

Friday, Apr 22, 2005 at 20:35
Interesting Melissa. I spoke to an auto elec today and he suggested exactly what you have, including the diode. Says he will install a Rotronics system if I want it, but his solenoid, diode and a couple of auto reset thermal circuit breakers will work just as well. His main point is that no matter where you are, the solenoid system is simple and can be repaired or 'worked around'. The more complex systems might leave you in the sh*t if you have trouble in the outback. Says he has done dozens of systems like this with no problems.

I was a bit suspicious of his simple approach until I read your post. Thanks.
AnswerID: 107887

Follow Up By: Member - Melissa - Friday, Apr 22, 2005 at 23:56

Friday, Apr 22, 2005 at 23:56
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
FollowupID: 364761

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