Dual batteries, can I wire them a bit differently?

[Patrol'n]

Howdy,

First of all, this is a little long winded, sorry in advance.

I'm in the process of installing a dual battery system in my GQ, since it's the rb30 version, there is a bunch of stuff in the way of the usual place next to the radiator overflow bottle. To get around this, I've picked up an ARB tray that fits against the firewall on the passenger side.

I'm about ready to bolt in the tray, (had a few small things to sort out to make it fit), and then I'll buy a battery. Since it's a smaller tray than the one above the wheel arch, I can only fit up to approx 65 amp hour battery in it. I've had the optima yellow top recommended to me, but I fear from measuring up, that it may be about 10mm to long to fit in the tray 😡. So I will pop down to auto one and try and see if one fits, but if it doesn't, I thought there may be another solution.

My boss has his triton wired up so that his primary battery is a dual purpose deep cycle and starting battery and all his stuff, (engel and lights etc), run from the primary battery. He uses the second battery just to jump start from via a button in the dash if he's drained his primary battery too much.

Given my troll is a 3 litre petrol, a 640 CCA battery starts it fine and they'll fit no probs in the new tray, so I could put a much bigger dual purpose in the original tray if this would work.

Does anyone have any experience with a setup like this, and are there any problems doing it this way, or does someone have a good suggestion for battery options? Tray size internal is approx 235mm, x 175mm, and about 200mm high at most. Obviously I'm looking for the most amp hours I can fit.

Thanks all.

[FNQGU]

It doesn't sound ideal to me but I understand your dilemma. For different reasons, I have no room in the engine bay for my Aux battery but needed the full size crank battery. The Aux was first installed beneath the vehicle but continued to get too hot, so I recently bit the bullet and moved it out of there and into the cargo area where it now sits snugly behind the end of one of my drawers, completely out of sight, and right beneath the fridge.

I don't like the idea of running the crank battery down and then jump starting, at least not if you do it regularly. It will dramatically shorten the battery's life. If you go ahead, you may want to set some sort of voltage alarm on it to prevent it running right down.

My 2 cents worth...

[threedogs]

when fitting the tray use large mudguard washers[penny].
I've seen plenty of trays rip the inner guard if not secured properly.
I dont think the way you want to wire it is a good idea or even best for battery
longevity. Buy a Redarc battery isolator cheap and effective. run all your accessories from your AUX battery
and leave your start battery for just that starting.
the isolator will give preference to your start battery then your Aux,
ensuring you'll always have 12 volts in your start battery
Not sure on battery case size that you need but talk to a battery specialist

[BillsGU]

I had the same problem with my previous 4by. I just rewired it so the small battery was my starter battery and the large battery was the auxilliary that ran the frige and eveything else. My theory was that if the starter battery was ever a bit down I could always use the jumper leads off the larger battery. I never had to do that as the set up worked perfectly. The starter battery was used only for the engine and I had plenty of amps (100Ah) in the now auxilliary battery for everything else.

Of course you will still need some sort of dual charging set up.

[Patrol'n]

I had the same problem with my previous 4by. I just rewired it so the small battery was my starter battery and the large battery was the auxilliary that ran the frige and eveything else. My theory was that if the starter battery was ever a bit down I could always use the jumper leads off the larger battery. I never had to do that as the set up worked perfectly. The starter battery was used only for the engine and I had plenty of amps (100Ah) in the now auxilliary battery for everything else.

Of course you will still need some sort of dual charging set up.

G'day mate, yep I did toss that idea around in my head too, I have the tray fitted now, so just waiting for an opportunity to check battery fit, I think I can fit about the right size starter battery in the alternate tray, so that's a real option, my only dilemma is whether any of the wires, relays etc that are connected to the battery now will give me problems if they are another metre and a half or so of cable away from the battery. Something to figure out...

[lhurley]

G'day mate, yep I did toss that idea around in my head too, I have the tray fitted now, so just waiting for an opportunity to check battery fit, I think I can fit about the right size starter battery in the alternate tray, so that's a real option, my only dilemma is whether any of the wires, relays etc that are connected to the battery now will give me problems if they are another metre and a half or so of cable away from the battery. Something to figure out...

Running the smaller battery as cranker is the way to go. Over a meter or so running sufficient sized cable shouldnt see any issues.

If you are still having doubts about rewiring a heap of stuff, i would run a sealed battery in the cabin.

[megatexture]

Sealed maintenance free still expell gas under charge they. Have a pressure release valve rather than a vent you would need Agm or a gel

[lhurley]

Sealed maintenance free still expell gas under charge they. Have a pressure release valve rather than a vent you would need Agm or a gel

What he said

[Patrol'n]

Running the smaller battery as cranker is the way to go. Over a meter or so running sufficient sized cable shouldnt see any issues.

If you are still having doubts about rewiring a heap of stuff, i would run a sealed battery in the cabin.

Ok, decision made, today I bought and bolted in a new battery for my main cranker, along with wire, terminals etc to mod it so the aux tray battery is set up with my primary. It's the best I could fit and designed to start late model commodores so should crank my 3lt petrol no probs. I'll upload some photos once it's done. I should be able to fit about a 100 ah deep cycle into the primary location.

While I'm typing, will I need to chuck the original primary battery straight away once the red arc is installed, or can I use it for a bit as the second battery till it dies then replace it? Obviously it won't last like a deep cycle, but it's still in good cond, any point to this or just go straight to the deep cycle?

Cheers all.

[megatexture]

You could use it and give you time to shop around for a deal but it won't like getting discharged but you may as well get your $ worth out of it.
As your using a smaller crank and the likelyhood of needing to jump start off your aux has therefor increased you could look at a marine battery.