I needed a convenient source of 12volt power that I could use to power the various electronic goodies that I’ve added to my 4Runner. I wanted to keep the wiring as neat and clean as possible, and I wanted to avoid tapping into the existing power circuits. I decided to install an auxiliary fuse block which would give me several individual fused circuits and would draw power directly from my battery.
It took a little searching to find what I was looking for. After visiting several electronics stores, I found an inexpensive fuse block that wasn’t too large or extravagant. I was surprised at the high cost of many of the ones that I looked at. I got this simple fuse block made by Buss for under $12.00. It is rated at 30 amps which is plenty of current for my needs. Since I mounted it inside my 4Runner, I didn't need it to be moisture proof.
I used zip-ties to mount the fuse block inside the driver’s side kick panel and ran an 8 AWG power cable directly to my battery. I also installed a high-current fuse where the power cable attaches to the battery. This is a very important safety step... that 8 gauge wire can carry a lot of current, and would very likely start a fire if it ever shorted. Any direct connection to the battery must be fused at the battery!
Another nice feature is that this fuse block has a stud for the power input rather than a wire or connector. This serves as a convenient non-fused power distribution point for any high-current devices (such as my stereo amplifier).
In the photo above, the large red wire is connected to the battery, and the large white wire is connected to my amplifier. To ensure a low-resistance connection between the two wires, I soldered copper lugs with large surface areas onto the wires and clamped them together on the stud. From the amp's perspective, this is just a straight power cable to the battery (Note: The amp has its own built-in fuses). My amp is not that big, so the 8 AWG wire is large enough. If I were to hook up multiple amplifiers, or draw any real current from the fuse block in addition to what the amplifier draws, I would probably need to run a larger wire from the battery to the fuse block.
I like the fact that the fuse block uses spade connectors to connect each circuit. This keeps things neat on the unused circuits. Without fuses installed, these terminals are dead. I use fully-insulated connectors on the live terminals to avoid shorts. I also insulated the power-input stud with a strip of electrical tape.
This setup provides constant 12 volt power to whatever is attached. Some of the fancier and more expensive fuse blocks which are available offer both constant and ignition-switched circuits. I personally like to wire most things up so that they work without the ignition having to be on, so that wasn’t a desirable feature for me. If I ever need ignition-switched power, I can always add another fuse block and use a relay to control it.
So what do I run off this fuse block? Right now the list includes: