Temporary Dual Battery System

**101RRS** · 10th December 2011, 02:51 PM

In due course I will be installing a proper dual battery system but not just yet. (heaps of other expenses at the moment).

My camper battery is a small 45 Ah and needs a bigger battery which I have. I want to put the 45Ah battery in the RRS battery box up near the ABS components for temporary use - I will not be putting in an isolator at the moment and will unplug it from the main car battery when not required. Yes an isolator would be better but not doing at the moment - will go in the final system I put in.

Heavy cable is expensive so my simple question is - do I actually have to run a negative cable from the main car battery to the aux battery or can I just connect the negative terminal of the aux battery to earth. Likewise do I have to run a negative cable to the rear of the car to the plug or can I just connect the negative at the plug to earth?

Thanks

Garry

**drivesafe** · 10th December 2011, 04:07 PM

Hi Garry and the earth stud in the auxiliary battery compartment is the perfect earth point for you battery.

You do need to run both a positive and a negative cable to the rear or you will have problems with voltage drop.

As to connecting the two batteries together. You should separate the batteries while you are camping and using the rear power set up, but if you are driving around with nothing drawing power at the rear, leave the two batteries connected, this will guaranty your auxiliary battery is always kept charged.

**101RRS** · 10th December 2011, 04:57 PM

Thanks - exactly what I was after - the car's main battery and aux battery will have an Anderson plug between them that I will disconnect when stopped overnight etc. I am not likely to go camping much in the RRS without the camper so this arrangement is just to cover those occasions where I need aux power on day trips.

Cheers

Garry

**Xtreme** · 10th December 2011, 06:12 PM

As a quick cheap battery isolator, that you don't have to remember to disconnect during overnight stops and that is always connected while driving is to connect the aux battery using a 70amp relay, energised from your accessories circuit.

**luke68** · 15th December 2011, 12:10 PM

Thanks guys,
did a search for someting similar and found this great thread. Need to get a caravan to Melb soon and only running 12v internal lights (2 halogen globes). Need something to charge the Vans battery whilst driving. this is the perfect setup short term. Won't be staying at any powered sights as I have pets.
Am I to assume that the second battery in the van won't be over charged if it is wired in parrallel? The alternator will think that it's only got one load but with more amps?

Cheers
Luke

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