Dual Battery Setup Part 3

Dual Battery Setup - Battery installed

Dual Battery Setup

Originally, my idea was to have a dual battery setup that was semi-portable. I’d be able to remove the battery from the boot so that I wouldn’t have to lug it around in the car when I didn’t need to. I’d also be able to arrive at a destination and carry the fridge and the battery away from the car if need be. As it turns out:

  1. I have never wanted to take the fridge out of the car on any of our trips
  2. The battery in the boot takes up too much room.

So I decided that mounting it permanently in the car somewhere was the way to go. But the question was ‘where?’

Battery behind the trim

When I was originally installing my dual battery setup, my cousin and I removed the trim in the boot and I mentioned to him how much space there was back there. I remember telling him that one day, I might put the battery in there somehow. And so that’s where I decided to put it.

But my problem was that there are no flat surfaces behind there. So you can’t just buy a battery tray, bolt it to the floor and put the battery in. You need to build yourself some kind of bracket. So I asked on a forum if anyone had any idea about how this might be possible and got exactly the response I needed almost immediately. The forum member had not only successfully built a battery bracket, but had installed it and also designed it in Trimble Sketchup, an application that I have recently started playing with.

His design didn’t quite fit my requirements but only some very minor modifications were required to get me on track. So using Trimble Sketchup, I made the changes I needed and ended up with something that I thought would be perfect for what I needed.

Battery Tray - Sketchup Drawing

Battery Tray - Sketchup Drawing

You can download the Battery Tray Sketchup File if you like. NOTE: Measurements should be double checked before you build it!

Basically, the difference between mine and his was that he purchased a battery tray whereas I designed in a rectangular frame that the battery would fit into. The frame is then supported by a cross beam and two legs that bolt into the vehicle.

Building the battery frame

Dual Battery Setup - Cutting the frameMy next problem was actually welding it together. I’ve had some very, very limited experience with welding, and also didn’t have access to a welder anyway. I was discussing this dilema with a friend of mine at the 4wd club and he told me that he was a plumber and welding was part of his job. He also owns a MIG welder and metal cutting circular saw. So we arranged to get together and build it up.

So on the day, I provided the design and he provided the know-how and we put together a frame that will be the last thing left of my car when they drop a bomb on it.

Putting it all together

Dual Battery Setup - Frame installed. Fits nicely.Once the frame was all done up, it was time to install it into the car. This involved drilling some holes at appropriate places and attaching it with 8mm bolts and nylock nuts. I then put the battery in place and noticed that the upper rear corner of the battery touched the outer shell of the car. So leaving it like that would eventually bulge the body work outwards. To fix this, I needed to lean the battery inwards a little so I cut come pieces off and old towel and put them into the back of the batteyr bracket. The battery now leans inwards slightly and is about 8mm off the body work so hopefully that will be OK. If I were to make the bracket agian, I’d move the battery tray about a centimetre inwards, away from the bodywork. Then there would be plenty of room for it all to fit.

After I’d ensured that the battery wouldn’t hit the body work anymore, I strapped it down firmly with some tie-downs that I got from Bunnings. That battery won’t move anywhere now!

I then wired it up as per the RedArc wiring guide pictured here, except at this point I don’t have the 3rd battery because I don’t have a camper trailer. But when I get one, it’s ready to plug striaight in:

1 RedArc SBI with 2 Aux Batteries

Dual Battery Setup - Battery installedIn addition to wiring up an anderson plug on the tow bar, I also wired in a small fuse box. From the fuse box I have then connected 3 12v power sockets in the boot. The existing one, and I’ve added two others. Into these I’ll plug in my car fridge, some LED light strips when I need them, and anything else that comes along. Drilling through the trim and cutting large holes in it to put the 12v sockets into was exciting. Not difficult, but there was a lot of checking and rechecking to make sure that the back of the sockets would fit once the trim went back on. It took a bit of courage to commit to it. But I’m very happy with the results!

Eventually I’ll also run a cable from the second battery to my UHF radio in the dash. At the moment the UHF is wired to my cranking battery and turns on and off with the ignition. That’s not ideal for me.

I’ll also attach a couple more 12v sockets to it that will sit on my rear draw system when it’s built. My son will then be able to plug in his iPad Mini and keep it charged when we’re out and about.

Dual Battery Setup - Trim back onWow, it seems like an awful lot of trouble for just 3 sockets in my boot… But once the camper comes along and I get around to finishing off my other plans, then there will be more.




Dual Battery Setup Part 1

Dual Battery Setup Part 2