Just completed a dual battery installation on my 2012 4.4 TDV8 VSE using the electrical harness supplied by:

https://www.ebay.co.uk/itm/L322-Range-Rove...3972504954

Notes to the electrical harness...
I was not overly impressed by the wiring and the connectors on the harness. The video link on the bottom of the flea bay product page shows a different harness to the one actually received. The connectors were not tight and needed nipping up to tighten them. None-the-less I have installed it and it does work.

Issues during installation...
The installation video shows the 5th Fuse being used for a connection, I had to use the 2nd fuse (rear wiper) instead as the 5th fuse location was blank.

The installation video shows the battery being installed on top of the load space, which would have been a total pain having to remove the battery when accessing the spare wheel, locking nut or scissor jack etc.

The quick release clamps on the battery are too bulky as they stop the plastic surround of the cubby hole being pushed fully home.

The wiring installed as decribed above:

Nice easy job

Is this so you have more juice to start it? 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
New Defender D300 90 on order so "Rory" will be going to a new home....!
1974 Series 3 Lightweight = "Millie"
My preferred specialist: www.glenrands.co.uk
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What are you using the 2nd battery for? I would think the guage of wire is much to light to carry any significant load. The loom can be easily lifted up and out of the battery area and run above the fuse box, it is now very vunrable if the battery moves as its not secured down.. A much more heavy duty instal can be made with a metre of decent cable and a voltage sensing relay capable of handling the current.
https://www.ebay.co.uk/itm/12V-140A-VOLTAG...Sw2WZbvm~U 2007 TDV8 VSE
2003 TD6 gone.
2002 P38a gone
1999 P38a gone
1997 p38a gone
1993 VSE gone
1992 VSE gone
1966 Series 2a with V8 conversion gone

@Wayneg - I agree that the harness is relatively poor quality and not engineered very well as stated in my first post.

Good idea on moving the main vehicle harness above the fuse box, will have a look at that over the weekend and report back.

The wiring kit does have a voltage sensing relay rated at 100A, again will be happy to upgrade the kit in due course.

Thanks for your input....

I recently sat in the car waiting for a friend and listening to the radio without the engine running and had to charge the battery in order to start the car due to loss of battery power.

Further, when I was installing the LED bulb kit I had left some of the doors and the rear open resulting in a flat battery.

I also drive between the UK and Europe several times a year, a distance of around 1,500 miles each way. The trips take about 18 hours drive time each way, two or three rest stops of about 2 hours each, during which I have a nap in the car.

I have installed the second battery purely as a backup to avoid a flat battery arising from the above issues.

John 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son

Last edited by 4434Morrison on 22nd May 2020 5:08pm. Edited 2 times in total

voltage sensing relay rated at 100A  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

@Joe90,

https://www.ebay.co.uk/itm/12V-140A-VOLTAG...3975468910

This kit will allow automatic charging of the secondary battery and the main original battery while the car is running. When the ignition is off the batteries will disconnect after a delayed time and the state of charge of the second battery is kept for weeks at a time meaning you will not come back to a Range Rover which wont start because it has a weak battery. 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son

Last edited by 4434Morrison on 22nd May 2020 5:48pm. Edited 1 time in total

It's not voltage sensing - it's switched via the ignition

Depending on your requirement - that may be better or worse than voltage sensing......

I'd guess from the photos, that there is nothing connected to the second battery - in which case, ignition switched is likely better. All drain is on the main battery - then when you turn the key, the batteries are connected together which gives some extra juice to start the car. Ideally turn the key, count to 20 then start if you suspect the battery is somewhat flat - that would put less strain on the cable.

A voltage sensing relay typically connects both batteries together when the alternator is running - and the voltage over a certain level. The time that makes sense is if there is a load on the second battery - like a fridge - that will be running when the ignition is off. It is intended to protect the main (starter) battery from draining.

You have two things: the "voltage sensing relay" (as Alistair says) which clicks in when the ignition comes on, and a 100 amp fuse on the main cable to the battery to prevent catastrophe  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Almost..... the relay isn't a true voltage sensing one - its triggered by the ignition - that's the independent connection that goes to the mini fuse - when that terminal gets power of roughly 12v it triggers the relay making a connection across the 2 main terminals

A true VSR monitors the voltage on one of the main terminals & triggers at something like 13.8 and will stay connected until the voltage drops below 12.7 at which point it will disconnect again. A VSR doesn't have an independent trigger connection.

The 100A could be either the fuse - or the relay, which is likely to be rated at 100A (likely both but prob easier to read off the side of the relay housing) - that is the maximum that it can switch - though usually they can handle far more than the rating - but I'd be less confident in the cable....

A VSR isn't expensive. Nor a 100a fuse.
Good peace of mind right?

. Cheers, Greg
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
2011 Vogue SE 4.4 with lots of toys in Stornaway

There's a fuse in the kit linked in the original post - but not visible in the pictures

VSR - depends on what you want. If it's sole purpose is to boost starting capacity, then you don't want a VSR - as it will actively prevent the second battery helping if the main battery is below 12.7v.......

The thin wires on the install in question would surely melt under starting load if the cranking battery was flat? I doubt very much that the relay from that kit is anything more than a standard 12v relay rated at 100a, it's just switched via ignition and not by voltage increase.
I think the best option for a proper VSR is the 2nd Red one explained in this video They are about A$50 25 quid. I have similar in my car.

https://www.youtube.com/watch?v=ew4zLC3ckm8 2007 TDV8 VSE
2003 TD6 gone.
2002 P38a gone
1999 P38a gone
1997 p38a gone
1993 VSE gone
1992 VSE gone
1966 Series 2a with V8 conversion gone

Many thanks for everyone's knowledgeable input on the dual battery system that I installed.

At this stage I only need the second battery as a backup to the main battery. I will in due course upgrade the cable and the relay as advised.

I will certainly re-route the main vehicle harness over the top of the fuse box this weekend as a priority.

It should not be difficult to produce a second battery harness of the necessary quality based upon the comments received about this install. This issue clearly is that the kit I purchased (as I suspected when I received it) is not quite up to the job.

I have a relative who is an electrical engineer. I will speak to him over the next couple of weeks and ask him to design and fabricate a proper kit, taking into consideration the comments received here.

Thank you to everyone for your comments and input.

John 2012 4.4 TDV8 Vogue SE Current
2015 E220 with AMG Sport Pack - Currently driven by my son
2010 3.6 TDV8 Vogue - Written off by my son