The last major component of the FJ Cruiser fit out was installing a dual battery system.  I have some electronics on board in order to help me navigate, research places to go, and stay connected, and all of these need to be recharged.  I can charge them while I drive, of course, but if I decide to stop somewhere for several days, I don’t want to have to make a choice between losing charge on my gear or jeopardizing my starting battery.

I considered several options for backup power, including a small generator and portable solar panels on the main battery, before deciding on the dual battery system.  I didn’t want to have anything external to the vehicle that might be at risk of being stolen overnight, or would be out in the weather, so that ruled out the generator.  Solar panels hooked to the main battery seemed like a good option for a while, but considering that I’d probably like to park the vehicle under trees when I camp, and they would be weather dependent, I’m not sure how effective they would be.  I can always add them later if it seems practical or necessary, though.  Two other considerations were price and ease of use — both of these options are considerably more expensive than running a dual battery, and both require some set up time, whereas with a dual battery I can simply flip a switch and crawl into the back for some sleep, no set up needed.  Lazy but practical.

The dual battery system I’ve chosen will charge both the main and auxiliary batteries off of the alternator when driving, and use an isolator to ensure that power only comes from the aux when the engine isn’t running.  I also added an inverter to get 110v AC.  Although I’ll give most things a try, I wouldn’t say that auto electrical systems are something that I’m very familiar with or enjoy much, so I opted to get a kit that was specifically designed for the FJ Cruiser, and included all the required parts, including battery tray, relay solenoid, cables, switch, fuses, loom, etc, and “easy to follow written instructions and diagrams, and CD with installation pictures.”  Sounds good to me!

First let me just say that I’m not short… but I could be taller.  And the FJ… could maybe be shorter.  So all of the following was done with me standing on a small step ladder so I could see and reach down into the engine bay.

 

After getting a grip on the instructions included with the kit, step one took an act of bravery on my part — drilling out the spot welds on an existing mount in order to remove it.  Let’s remember that I’ve owned the FJ for exactly 6 days, so the idea of hacking into it was a bit nerve wracking!  Here’s the mounting point before I started working, and then after, with wiring harness moved and welds drilled out.

And after a bit of fiddling and fussing, I got the auxiliary battery tray installed.

Then I bolted the relay solenoid to the side of the tray, ready to be wired up.

On the advice of a friend (hi Gav!) I got a deep cycle battery to serve as my aux, so the next step was to put it in and bolt it down.  I ran the battery cables from the positive aux terminal to the solenoid, and then from the solenoid I routed it along the firewall and opposite wheel well to the positive main terminal.  I grounded the negative aux terminal to the rear engine mount.

 

As you can see above, I then wired up the switching solenoid, grounded it to the frame, and ran the wires along the firewall to the driver’s side of the vehicle.  The instructions called for drilling through the fire wall, but I found that I could use an existing access point and avoid the trauma of taking a drill to my vehicle again!  (Also notice how clean the engine compartment is.  Honestly, this is like a new vehicle!)

I removed a switch blank to the left of the steering wheel, but unfortunately the rocker switch provided with the kit was slightly too big for the slot, so I had to trim the slot to fit.

Then I did the final wiring of the switch into the fuse panel, and connected it to the switch power cable that I had run through the firewall.  Then it was time to test the system and check voltages.  Yay!!! Everything worked!  I cable tied everything in place at this point, as some lines were running close to the exhaust manifold and I didn’t want to risk any damage.

In order to have 110v AC power to charge my computer and anything else I need to run, I bought a standard 400 watt inverter, which should cover anything I need.

So it’s done, nothing exploded, and although it’s been a lot of work, I’m feeling pretty good about the end result!  I’m one step closer to the road!