Dual battery in P38A

**drivesafe** · 15th March 2011, 08:48 PM

Originally Posted by glenhendry

OK, I am going to go for the underbonnet system and I will document it.

Anyone care to comment on where I connect the positive terminal of the auxillary battery to? In the following link here, the diagrams suggest connecting the aux battery positive terminal to the 'accessories' or 'auxillary load'. For me, I want that to be all of the cig lighters and radio etc. Can I just wire that straight back into the fuse box so all the cig lighters (front and back) are powered by the aux battery when the engine is off. Surely I dont have to run a separate circuit?!

Hi glenhendry, I make and supply the SC80 and the two “thin” wires are 6mm2 marine cables. Note thats not 6mm AUTO ( 4.5mm2 ).

So the two outputs are nearly the same size and current capacity as a single 6B&S cable.

Next, for what your planning, you can simply run a new supply cable from the auxiliary batttery, via a circuit breaker to the vehicle’s existing fuse panel and replace the original vehicle's supply cable coming from the ignition switch.

This will not only supply the power for your accessories from the auxiliary battery but it will bypass the ignition switch so you don’t need to leave your keys in the vehicle.

Last but not least, you only need to run 6B&S cable to be able to jump start your RR from the auxiliary battery, and that includes where the battery is mounted in the rear.

**glenhendry** · 15th March 2011, 10:28 PM

OK people. I am afraid that it wont work (for me). I tried hard, and although I can get the batteries in there, side by side, under the bonnet with the OEM battery tray removed, there just isnt enough room to get the batteries flat and level due to the inner guard slope AND get the bonnet closed.

This may work better if you have slightly smaller batteries, but I have a 950CCA main (335mm long) and a 650CCA 95AH deep cycle auxillary (305mm long) and they were too tight.

See photos. It looks like I will be relegating the aux batt to the spare wheel well next to the LPG tank. I am not looking forward terribly to running the cables, but at least it will be invisible and leave the OEM battery tray and cover which looks nice!

Stay tuned.

DSC05698small.jpg

DSC05699small.jpg

DSC05700small.jpg

**rofosixone** · 15th March 2011, 11:02 PM

if not under bonnet and not in spare tyre well , type photobucket on your google search box ,than type p38a once in it and click most viewed page"s and see my set up if helps ? ,click that rear battery fit pic for story underneath it ,how i did on mine if helps.
footnote ,yes rear neg earth cable to body (under rear side window) but dont forget to fit extra neg cable from frount battery to alternator if realy want it to charge up as i found and must be sealed battery if used inside the cabin /safety or roll over wise .
currently right now ,pic no 8 on page one of popular p38a page is what you might be interested to see the most.

**p38arover** · 16th March 2011, 06:45 AM

Originally Posted by glenhendry

OK people. I am afraid that it wont work (for me). I tried hard, and although I can get the batteries in there, side by side, under the bonnet with the OEM battery tray removed, there just isnt enough room to get the batteries flat and level due to the inner guard slope AND get the bonnet closed.

I didn't say the ones I saw were big batteries!

I think they were Optimas.

**Hoges** · 16th March 2011, 01:09 PM

Placing the aux. battery under the bonnet can have less desirable consequences... heat sink effects on hot days (reduced battery life) and an additional 26kg over the front axle

... probably get more service life and better suspension compliance if placed in the 'cubby' space above the floor in rear compartment on RHS.

BTW what's the red cylindrical thingo beside the fuse box in the engine compartment?

cheers

**glenhendry** · 16th March 2011, 01:21 PM

NoS cannister. NOT.

Its my hot water transfer for camping showers. It steals a feed from the cabin heater hoses before they get to the heater or the LPG converter. Since install, I have smelled LPG from the car a few times

but that's another story. Hopefully it is as simple as giving the converter more hot water flow, otherwise I have buggered something up...

**Rat_RR02** · 4th September 2011, 05:52 AM

Hi,

I was thinking of doing a dual battery in my truck a few years back (never did though) and I am certain there was plans/drawings for a dual battery tray to replace the single battery tray over in rangerovers.net forums. I will see if I got a copy of it and post back here later on. I ended up just running heavy wires to the back along the frame with an anderson plug and a heavy duty connector in the boot for my camper and fridge.
cheers, Mick

**996TURBO** · 5th September 2011, 06:28 AM

Originally Posted by glenhendry

OK people. I am afraid that it wont work (for me). I tried hard, and although I can get the batteries in there, side by side, under the bonnet with the OEM battery tray removed, there just isnt enough room to get the batteries flat and level due to the inner guard slope AND get the bonnet closed.

This may work better if you have slightly smaller batteries, but I have a 950CCA main (335mm long) and a 650CCA 95AH deep cycle auxillary (305mm long) and they were too tight.

See photos. It looks like I will be relegating the aux batt to the spare wheel well next to the LPG tank. I am not looking forward terribly to running the cables, but at least it will be invisible and leave the OEM battery tray and cover which looks nice!

Stay tuned.

DSC05698small.jpg

DSC05699small.jpg

DSC05700small.jpg

Hi,

Is it a fire extinguisher you have there?

**glenhendry** · 5th September 2011, 10:04 AM

Originally Posted by 996TURBO

Hi,

Is it a fire extinguisher you have there?

Ah, better. See 3 posts down, it is hot water transfer for camping showers.

**996TURBO** · 6th September 2011, 05:47 AM

Originally Posted by glenhendry

Ah, better. See 3 posts down, it is hot water transfer for camping showers.

Very interesting. Have you tested it yet? I'd like that under my hood but i'm not sure i have a place to install it.
Already have some LPG converters and HD air compressor in there

Thread: Dual battery in P38A

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Two large batteries DO NOT FIT in a P38 under the bonnet

not under bonnet ?

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