Dual Battery Project

OK - here we go! This has been going on for a little while as a secret black-ops project on a strictly need-to-know basis, but it's starting to come together, so it's time to unveil it to the world!

Justin from the PCOA forum and I have been working on a solution to the dual battery problem with Pathfinders. Most people with Pathfinders either:

• Use the Pirana tray to mount a second battery under the bonnet next to the main, or
• Use an AGM battery in the boot, in a box
  

Well, just to be difficult, I didn't like either of those options. Heat is a big killer of batteries, so I didn't really want one under the bonnet to start with. I know a lot of people have them there and don't have any troubles, so this is probably more of a "nice to have" as opposed to a "definite problem", but that was my starting point. However, I also wanted at least a 100Ah battery, and the biggest you can fit under the bonnet is a 60Ah.

So that basically dictated that I put the battery in the back of the car. I was always planning on using an AGM battery, so having it in the car wasn't an issue. However, I really didn't want to loose the space inside the cargo area. We tend to take so much stuff away anyway that the back's pretty full - I didn't want a battery box in there as well. Plus, I want to retain as much of the factory-look of the car as possible, which will help if we ever want to sell it.

So - what to do? Well, Justin and I have come up with this ingenious plan:


I intend to squeeze a 100Ah AGM deep cycle battery into the void behind the rear passenger wheel. It's just about the perfect size! This will let us run a 12v fridge down the track, as well as providing power for camp lighting and all the other odds and ends that make life comfortable.

I'll be building a battery carrier that's similar to this:





It's my intention to have the battery pretty much open to the elements, so that it's easy to clean out. My original plan was to try and fully enclose the battery in it's own box, but that became too heavy and too complex. So long as we have good stone guards to protect the casing of the battery, there is no reason why it won't be completely happy tucked up under there.

The design of the carrier also ensures that if we were driving off road and dropped the back of the car down onto a rock, say, that the battery would be protected from the force of that impact, and wouldn't be squished against the underside of the car, thus shorting it out and exploding the battery. The HD steel uprights will be able to take quite a wack, and protect the battery itself from any force. Plus, it'll be slightly higher than the spare tyre anyway, which is currently the lowest point under the rear of the car. Hence, it should take the brunt of any hits, and leave the battery holder untouched. By using the flat plates on top, we'll be spreading the load over a much wider contact patch on the floor of the boot.

So that's the tricky bit done. I still need to build the carrier, but it's my next job. The measurements that we've been working of are still reasonably fluid, and we'll make the carrier to suit the exact battery that we end up going with. Currently, that battery is going to be a Remco 12-100DC, a 100Ah deep-cycle AGM battery. But it depends on who has what in stock for what price when I finally pull the trigger, which will hopefully be today or tomorrow.

But the battery is only one part of the puzzle. Up front, we need a dual battery isolater to protect the MAIN battery, and ensure the charging of both batteries is carried out properly. I decided fairly early on that I wanted to go with a Traxide controller, based on the good feedback that others here have for them. Traxide are also a local QLD-based company, so I like to support them. The way the controller works is also a bit different to the run-of-the-mill controllers, in that it doesn't automatically isolate the AUX battery when you turn the car off - it allows the accessories to draw down the MAIN starting battery a bit before cutting it off. This ensures that you'll still have enough power to start your car, but gives your accessories (fridges, etc) additional run time by "borrowing" some voltage from the MAIN battery, and in effect lets your AUX battery last longer. It also prioritises charging to the MAIN battery so that short trips will see you always able to start your car.

Based on the Traxide controller, and using some diagrams taken from the traxide site, I've come up with the following wiring diagram:

The difference about this diagram mainly surrounds the inclusion of the marine switch to bypass the controller and link both MAIN and AUX batteries. Because of the difficulty in accessing the AUX battery once it's mounted, I needed a way to link both batteries together to jump-start the car in the event of a problem with the MAIN battery. After discussing the various options with Tim from Traxide, we settled on the above diagram as a good solution. Indeed, Tim had just conducted some experiments a month previously where he basically had hooked up the exact same system, and had been able to easily start his Range Rover from the AUX AGM battery. So that gave us the confidence that our plan was good, and would work for what we needed.

You can clearly see in the above diagram the second Anderson Plug and breaker that connect the AUX battery into the rest of the car. That will let us wire the battery to the new holder, bolt the holder up onto the car, and then connect the wiring in the car to the battery. The front and rear Anderson plugs give us the ability to run exterior accessories off the car, as well as running a 12v system in the camper trailer which we hope to get one day. The front Anderson plug does double duty as a charge point for a CTEK battery charger to keep the AUX battery topped up and in good condition if the car needs to sit in the garage for an extended period of time.

For the last little while, I've been collecting the bits and pieces that I'll need to make this all work. Traxide supplied one of their uprated SC80 controllers, along with a full wiring kit that includes everything I need for the proposed setup. Big props to Tim from Traxide for all the help he's give me - it's been a pleasure doing business with him thus far and I can't recommend him highly enough.

This is the kit they supplied:

That wire is massively heavy duty stuff, and weighs a ton! However it means that we'll get good power supply throughout the car, and much less voltage drop than we would otherwise have. Less voltage drop through the wires equates to a more efficient system, and faster recharge times for the AUX batter - all good things!

I've also collected the following items:

Along with some misc other bits and pieces. I even treated myself to a brand new ratchet crimping tool with a couple of different interchangable dies, to make crimping the big connectors child's play (so long as your child is a 180kg professional wrestler).

The volt meter, fused switch panel and power points are all going into a panel that I'm making up for the rear of the vehicle. It will be mounted inside the cubby-hole on the driver's side, and will hide behind that removable trim panel. This shows the basic layout of the panel.


The volt meter will be hooked up to both batteries via the 3-way switch, thus giving me an easy way to monitor the status of both MAIN and AUX batteries using the one meter. The switch panel will run the 2 cig lighter sockets and the 2 PowerPole connectors mounted underneath, as well as keeping 2 switches free for some future use. One idea is to mount a waterproof cig lighter socket on the roof rack for camp lighting, another would be as a master switch to isolate a water pump. Having the switch panel protected in the cubby hole behind the clip-on panel means that through the week you don't even know it's there, and when loaded up nothing can accidentally fall against one of the switches and turn it on (bad if it's the water pump circuit!!!) or off (bad if it's the fridge circuit!!!). I'm still deciding what I'm going to wire up to the switch marked "Bilge Pump".

On the weekend I got started on the difficult side of the project - actually putting all the parts together! First job was to mount the electrics under the bonnet near the MAIN battery. To do this I'd previously spent a night with a sheet of cardboard, some tape and a ruler to make a template of the bracket that I wanter. Then, on Saturday it was down to Bunnings for some material and supplies:


I traced the outline of my template onto the 2mm checkerplate ali, and attacked it with the jigsaw.


Once the outline had been made, it was time to drill the large hole for the marine switch. Because to the restricted vertical space, I needed to mount the marine switch underneath the panel, with the switch itself poking up through. Luckily I had a holesaw in the right size.


Once it was all cut out, I bent up the sides and feet of the bracket using a clamp, a piece of ali bar, and my big hammer. Then it was time for the big test - was it even close to what it should be?


Perfect.

It was then an easy job to drill the mounting holes for the equipment on the panel, and bolt it all together. Time then to trial-fit it under the bonnet again to check clearances to the underside of the bonnet (hint - one of the fuse blocks is EXTREMELY CLOSE to the underside of the bonnet when it's shut! It doesn't break the plastic cover, but there can't be much in it!!!), as well as the original fuse box and brake master cylinder.


That was as far as I got with the project over the weekend. I've started to wire up the front panel, and hope to have it finished during the evenings this week. I also hope to be able to make a start on the rear panel this week, with a view to starting construction of the battery holder over the weekend. We've got a deadline for this project - just under 2 months until we leave on our Christmas holiday - so it's got to be done by then! I suspect the battery holder will take some time to get just right, but the remainder of the project is pretty straight forward.

So that's where it currently stands, and that's the plan going forward. Hopefully it will all come together and work brilliantly! Otherwise I'll look like a bit of a goose. But so far, every indication is that it should end up as a good, easy to use and rather invisible system.

Stay tuned for more updates as and when they happen!

Bullbar - Job Done

There you have it - the final product! After two weekends and a couple of nights through the week, the bullbar is on the car and wired up. The indicator and parker light repeaters are working perfectly, and the fog lights have been wired in with their new switch and work a treat.


The aerials have been re-routed down onto the bar from their previous positions on the side of the bonnet, and all mounted up correctly. Where the old Z-brackets have rubbed through the paint, we wiped down and used some touchup paint to cover up the bare metal and prevent any rust.

All the wiring's done - all the joins are soldered, heatshrunk, wrapped in electrical tape and encased in split-tube, so they should last a while without giving any trouble. Everything's safely secured away with cable ties to keep it all in the right spot. We wired the switch for the fog lights into the parker light circuit, so if the fog lights are on, turning off the headlights turns the fogs off as well. The Subaru works this way, and it's really handy.

There's a couple of little jobs left to do that I'll do over the next few weeks. None of the bolts to attach the brackets or the bar came with spring washers. The last thing you want is for the bar to come loose after driving on corrugations for a couple of hours, so I'll need to source a bunch of different sized stainless-steel spring washers, and put a couple on every bolt under there.

And lastly, I've not yet re-fitted the inner guards. They need to be trimed down a bit so as not to funnel water up into the motor's air intake snorkle. I'm not sure what's involved in that yet, so will leave them off until such time as I can sort it out. I'm hopeful that I can ask a couple of Pathfinder owners with the same style of bar to send me some photos of what they've done to alleviate the problem. No sense re-inventing the wheel, after all!

All in all, we're pretty happy with how it's ended up. Once I get a change to get it out of the garage I'll take some nicer pictures in the sun. But for now, I'm pretty happy that the job's done!