Looking to Add a Second ( Auxiliary) Battery for fridges etc
 

HI Everyone, first time Poster - 1 Hour lurker, from Melbourne Australia

I have a 2013 R Design and am wanting to install a second battery for running a fridge/ Freezer etc .

I'm very curious as to where anyone has mounted the second battery? What brand, size and configuration did you use? How did you mount it etc.

Scenario 1 - The Ideal situation:

Ideally speaking, I would like to mount the battery and isolator near the main battery

Then the plan is to have two 12V plugs under the current plug in the rear.

The run a line to the 1st row centre console for another plug and 1 to the third row console for a second fridge mounted on the 2nd row 'Booster' seat

From there I'll build a removable floor compartment to mount the fridge etc

Scenario 2: A workable ( but not ideal) solution

The option I have thought about is to mount the battery in a box and store in the cabin ( on a to be constructed removable platform board behind the fridge when its mounted) In this i would need to mount the isolator in near the main battery and then run wiring up to an Anderson plug in the cabin ( again on the passenger side) so that the second / auxiliary battery is removable.

Any thoughts, pictures, diagrams and the like are very much appreciated.

Before you go to all the hassle, what type of engine and battery is currently fitted?

The XC90 came with various battery sizes for various engine types, and the largest battery is a 90Ah, as fitted to the mighty D5 diesel (which I have)

The XC90 also has a permanent 12V power point in the rear, which is monitored and the dashboard DIM tells you if anything is plugged in and running when the car is turned off. Ideal for a fridge.

I would do these steps:
1. Upgrade the battery to a 90Ah (if not already fitted)
2. Fit a CTEK battery sense to keep an eye on battery charge on your phone (awesome device, I have one)
3. Install a 10W solar panel in the dashboard to help keep the main battery charged when the sun shines (you are in Australia after all!). This helps compensate for fridge power drain, as a fridge does not run continuously.
4. Use a modern car fridge with high efficiency, and under voltage protection

But if you really want a 2nd battery just for a fridge, then install a small lead acid battery or lithium battery (better) beside the main battery.
Then fitting of battery switches, charging indicators etc is much easier.
Make sure you have a fuse panel also installed!

behind the

If you really do need an additional battery, I guess you are looking at a split charge system which is commonly used for caravans, except the auxiliary battery will be in the car. There are a lot of pre-wired kits available to do this on e-bay, which will have the voltage sensing relay and fuses etc. All I would say is don't get a cheap one from China.

But do you really need a extra battery? If you run the fridge whilst the car is driving then that will always be fine, when you are stationary and the car is locked on sunny days when the internal temperature of the car gets high, most fridges wont cool anyway and you may be better off with a larger coolbox and lots of gel packs.

But if you do fit a second battery, there is a lot of room in under the boot floor besides the main battery, even if you can't find a large battery to fit you may be able to fit a number of smaller batteries - but stick with one larger one if you can as they are more efficient and cheaper than several smaller ones.

Generally camping fridges are only used on 12v when driving , they generally have gas or Mains power to keep them running once you get to your destination .
Your 12V car battery will not keep a fridge going for long ....

Thanks for the feedback and aeveryone has given lots of great advice - The reasons for needing the second battery area a few fold -

1. Running two fridges during the day whilst touring, and then they need to run over night ( one will be acting as a fridge the other as a freezer. Running two will flatten the starter battery. Given the remoteness of the areas we are travelling to, having a battery run flat is not a good idea! :)
2. with reference to point 1 - the second battery can momentarily act as a starter battery if needed.
3. At the camp sites we may stop for a number of days which then means charging of devices, running fridges and the like, solar may not cope with this
4. i may look to add solar as a top up mechanism at some point when the very large trips occur, not for immediate.
5. the Kids also like their USB disco lights and along with the ability to watch projected films etc, Mainly Frozen and that damn Let it Go Song
(AAAAAAAAAAAAAGGGGGGGHHHHHH) so again lots of power requirements.
6.adding the dual battery also allows for the maximum in storage to be maintained, without the necessity for a battery box etc.

I should also add :-

the vehicle is the D5 with 90 AH and battery to go in will be at least 90 AH or ideally 110AH. (Bigger the better!)

I'm also constructing a sliding platform and housing for the Fridge and another storage compartments that i'll post diagrams, pics and measurements too if anyone is keen.

The whole structure is designed to be removable (within 10 minutes) to access the Spare tyre points / tools etc. and to provide protection to the current back area.

If you want a bit of a DIY project for power on the go, this is a very interesting solution.

Thats quality work!

Sounds more like you need a diesel generator!!

I don't think solar is any help to you - the small panels to keep your battery topped up are typically 10-15 watts - that equates to 1 amp at 12 volts. A larger panel that would be useful (say 100 watts or more) would be bulky and difficult to carry. You could look at multiple, smaller panels through a MPPT charger (much better than PWM).

The traditional "split charge" set up will not allow you to use the second battery to start the car in the event that the primary battery becomes discharged, the relays, switching and cabling etc. are nowhere near man enough for the power involved and hence the second battery is isolated during started. You could use jump leads though.

I think your best bet will be a large leisure battery (or array of them) and a split charge system. It sounds like some of the equipment you will be using may be mains powered, in which case go for a pure sine wave inverter - they're more expensive but more efficient.

Hey AussieMatt,

Sliding platform sounds great. I'd be very interested in seeing this or if you wouldn't mind sharing the plans that would be fantastic! Originally from Aus myself and used drifter kitchens all the time but they are hard to come by in the UK. Just returned from a family camping trip and could really see one being useful. Cheers.

Joel