Been wanting to fit an Axillary battery for some time. not for any specific need or reason. Just as a proof of concept really.
I'm still waiting for various cables and connectors to turn up from eBay, but the battery itself is in and ready to hook up. I've put it on a rubber mat to stop it moving around and also to catch any acid spill, although I don't think this will be an issue.
As for hydrogen gas given off whilst charging, directly above is the forced air ventilation system which extracts air so this should remain fairly well vented at all times.

As for linking it in, there is already a 100Amp cable in this area I intend to use with a 40A maxi fuse in-line to ensure absolute integrity of existing vehicle wiring. I think initially it will just be an additional battery, rather than having a split charge/relay system. So I will just get extra capacity rather than redundancy.

When installed and the floor is back on, you cant tell it's there:

Click image to enlarge

Where are you going to mount the fire extinguisher?

Hey Dan. Yup I tried this when I moved to a full fat from a D3. The D3 has 2 battery trays under the bonnet and it's very useful for things like Engel fridges. Basically it preserves your starting battery.

But, in the FFRR you only have a 100a cable if you tap into the big red one just above where you put the battery so unless you split charge it it A: Won't preserve your main battery, and B: You won't get enough current up that cable to start the engine.

Point B is the important one though. If, for any reason, you happen to end up with a flat main battery, unless it is split charged there is the possiility that the engine will try to pull massive currents through that 100a cable during starting. Could get rather hot. Best solution is to use a large (200a) relay to isolate it when the engine is not running. Got some bits in the garage if any use to you - will do exactly that.

I tried an Optima yellow top, mainly because it was a sealed gel type so gassing wouldn't have been an issue. It fitted well but the reality was that it was just another few kilos in the car. No perceivable benefit and it was taking up the space where the towbar gets stored.

Interested to know what you might use it for though.

Dom

Katash wrote:

Where are you going to mount the fire extinguisher?

I could suggest somewhere. 

Dom,

Initially it will just be extra capacity, the battery that's in there is about 50% of the power of the main battery. I bought a gel battery but unfortunately was a smidge too big to fit in the hole, I think Optima's are too big too

I'm aware of the 100Amp cable limitation, thats why there will be an inline fuse rated to 40A and I'll see how often it blows. In reality, it just means I can run the preheater that little bit longer, or forget to turn the lights off or longer etc. As instead of discharging the main battery 50% and then not being able to start, it will discharge only about 75% and should still have enough power to start the car.
Obviously as you say it's not isolated so if I left the lights on for 24 hours then they will both be flat and I'll still need a jump.

The other consideration is installing a relay and running accessories off of the battery like a coolbox or CarPC in standby etc. But this is a low down the list requirement for me - I would settle for a little more resilience, rather than getting a flat battery after a few hours of detailing with the radio on etc.

The main reason I've done this is because I've only seen one other aux battery install and that was on RR.Net by a guy in the US. 

Nice Dan, thanks for sharing.
I intend to do a similar install, but with the split charge system and relay in addition to a big fuse ( I am thinking 60A), cos I want the additional battery for fridge, plus the split charge system so I can connect my trailer (with 2x 105ah) to the same system, so the cable from the front of the vehicle would only ever charge the dual battery, and the split charge system would not allow them to operate in parallel.
How I will get this past LRSA is another worry - I have been trying to get info on the dual battery system from the armoured RR from them in the hope that they would approve fitment of a genuine accessory, but to no avail

Please post updates as you progress

Baben, take a look here. Specifically made for LR vehicles. Got a very good reputation on the D3 site as well.

Dom.

http://www.traxide.com.au/SC80.html

It does, of course, mean you'll have a reasonable amount of spare amps to power your winch...


 Not sure you should be reading this bit.

im keen on this one aswell and i have been thinking similar thaughts i.e

-gel type battery
-IBS split charge
-1000w ac inverter

to run a small kettle and fridge and other small electrical items


keep up the good work and research

 onto no6 Range Rover

Everyone needs a hobby

Thanks Dom, that traxide looks very simple and easy

Finished the install today.

For a basic install like mine you will need:

Battery (no more than 7 inches wide and 7 high, length is less important but this one is 9.5 inches)
Battery terminals - I chose these No Spark/quick release ones.
Cable - I bought a cheap set of 100Amp jump leads as this was the most economical way of buying the cable.
Maxi Blade Inline Fuse Holder - Again, eBay
Misc crimp connectors, depending on your setup. I used a copuple of ring crimps as that seems to be the factory style.

Click image to enlarge

nice one dan, looks like it was out of the factory with it.. have you had a chance to see if you get low voltage warnings come up when do a scan V8 facelift Range Rover Autobiography 22" wheels.
1976 Harley Davidson Iron Head Sportster

I'll have a scan after a week or so, see if anything comes up. I've been getting HDC inactive recently, due to low voltage I believe.

Not had that message at all today.  

Dan, what's holding the battery secure?

Is there a clamping mechanism of some sort?

If I have battery issues with the FF I get, this is definitely an option I'd be looking at. Researching my first Range Rover purchase

Dan

any update? Glad to see people are keen to see full use out of the FBH. If you have no problems, I think I might do this mod myself too.