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The Range Rover P38 Dual battery installation page.

A dual battery system that give some kind of power redundancy is welcome for many Range Rover P38 owners this is how I did mine!


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My Range Rover P38 1999 Westminiter edition 4.6 HSE
You are free to take part of my experience and idea's but keep in mind,
don't blame me if anything goes wrong :0)

Upgrading my Range Rover P38 with a dual battery installation.

During the winter I have my car parked at the airport in the northern Sweden for
sometimes up to three weeks without being able to drive it or to have the battery
connected to a charger. And quite often the mercury shows temperatures below -20C
where the car is parked.

We all know that a P38 have quite a lot of electronics that require power all time
this is a problem for us that are not using hour car for daily drives but an unknown
problem for they who doe's.

The last two winter I have kept a spare 70A car battery in my trunk along with
jump wires to be sure to be able to start the car when I arrive at the airport. This
is however not exactly convenient since I have to open the bonnet each time I get
there (I know it might me considered as, "Only a problem for the privileged") however to solve this issue
I have decided to upgrade my Range Rover with a dual battery installation whit a
battery selector switch and a battery charger system that are easy to handle and
doesn't require the bonnet to be opened.

Listing and images of the parts for my dual battery system

  • 50mm2 (0 AWG) thin plated copper wire (Less prone to corrosion that bare copper strands).
  • Battery changeover switch 4 position [Batt1] [Batt2] [Batt1+Batt2] [Off].
  • Cable terminals.
  • Diodes
  • Switching battery charger
  • A 2nd battery
  • Maybe some battery monitoring system
50mm2 tin plated copper wire with rubber insulation for dual battery installation

10 meters of 50mm2 tinned copper wire
I hope I bought enough.

My intension is to get a low loss system
despite the long wire run from the spare
tire compartment where I intend to mount
my 2nd battery. I want to be able to start
my engine from this 2nd battery in case
of a long time parking situation that most
likely will drain my main battery.

I'm not sure yet where to run the wires they
are rather bulky those 50mm2 wires!

Battery selector for dual car battery installation
The battery selector of my choose was picked
from a boat assessorie store and is a heavy
duty switch that can do this job well.

I will try to mount it at a convenient place.

The switch will allow me to chose between
Battery 1 or 2 or booth in parallel.
I can also disconnect both in case I want.
Heavy duty crimp tool for battery terminal lugs
Terminal luggs that can take 50mm2 (AWG 1) Wires
Heavy duty terminal crimp tool. This is the
low cost version that should be used in conjunction with a heavy hammer!
50mm2 (AWG 1) Terminal lugs. They
come in different versions so chose one with a hole that suits your needs.

Spin off effects from the dual battery installation project!

Since I de sided to put the 2nd battery in the spare tire compartment I felt that I
should get some alternative puncture recovery gear. I decided to buy a tire repair kit.

I know that a kit like this isn't a complete replacement for a spare tire but I will at least be able to recover from small punctures caused by smaller tire damages.
For more adventurous trips I will still be able to throw a real spare tire in to my boot!

Removing the spare battery will save me space not only for the 2nd battery it will
also leave room for some tools and a portable 12V air compressor / tire inflator.
This is what I bougt.

T-max portable tire inflator / compressor A portable 12V air compressor for
tire inflating I went for a T-max modell P/N 8016601.

Beer bottle for size reference only.

I have bought several crapy tire
inflators at petrol stations and
various car acessory shops so I
did expect this to be something

It was at about 100euro the most
expensive 12V compressor I have
bought, however when I unboxed it
and made my first test it actually
exeeded all my expectations!
12V bush ranger compressor for 4x4 cars and large tires The  T-Max 4X4 Adventurer

  • Maximum air flow
    160 Liters per minute
  • Voltage    DC 12 Volt
  • Motor output power
    537 W (0.7 HP)
  • Maximum amperage draw
    45 Amps
  • Maximum working pressure
    150 PSI
  • Cylinder diameter
  • Maximum ambient temperature    60°C
  • Minimum ambient temperature    -40°C
  • With amperage overload
    protector, Press to reset
  • Recomended on/off cycle
    40/20 = 40min on / 20min off

While the compressor itself and the pressure quick connects feels solid and have that
PRO feeling I can't say the same about the pressure gauge and tire valve connector.
However they are suficient for emergency use!

The value of this kit is good anyway and the compressor unit will probably last for a
couple of generations (Yes it feels that good).

Other compressors that was under consideration was the more expensive VIAIR 450P
There are lot of other options to I'm however happy with my choice :0)

Plugga II Car tire repair kit for large 4x4 car tires

One more thing, the tire repair kit!

There are several different brands
and types of tire repair kits out there.

I went for the Plugga II kit for no
other reason than that it seamed to
be "great stuff for the money".

I buy lot of my stuff at eBay but
both the compressor and the tire
repair kit can be found at many
online shops for 4x4 cars.

Car tire repair instructions
Plugg-A Car tire repair kit Plugga II instructions for tire repair.
It's not that hard to perform.
I guess most normal handyman would
be able to repair a small puncture
with this kit.

The hardest part is probably to find
and get access to the damage!

Schematics and the actual instalation

This section will hopefully be completed during summer of 2011.

Until then I will keep adding stuff like schematics and different Ideas to this page soo keep looking back for more!


Comments, suggestions, requests here!


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