Power Source Switch Box to Switch From AC Power to Battery

The idea of the switch box is to be able to easily switch from an AC power supply to battery backup. The switch box is part of my PVC Amateur Radio “Go Box”

The reason I made this switch box is that I am an Amateur Radio Operator and I wanted to be able to operate the radio when the power is out or in the field where there is no AC power. It's helpful to have a way to easily switch power sources, so I made a relatively easy switch box.  

Parts Used

1 – Toggle Switch - 2 Position DPDT ON/ON Toggle Switch with screw terminals.

6 – 12 gauge size M4 fork spade crimp connectors

4 – 12 gauge size M6 fork spade crimp connectors

2 - 12 gauge crimp butt connectors

2 – Male in line quick connect crimp terminal

2 – Female in line quick connect crimp terminal

12 feet of 12 gauge RED stranded wire

12 feet of 12 gauge BLACK stranded wire

1 - Inline fuse holder rated for at least 30amps DC and fuse

Wiring harnesses that came with the radio

1 – 4” x 4” x 2” PVC Junction Box

Tools Used

Wire cutter/stripper

Terminal/connector crimper

Phillips Head Screwdriver

Drill with a 1/2” and 5/8” bit

Label Maker

I used an extra wiring harness for the radio that I had and not the original one, just in case I really messed it up. I did shorten the leads of the wiring harness of the radio.  I used in line quick connect crimp terminal on the leads so that I could push the wires though a 5/8” hole in the switch box along with the other wires. The white connector that plugs into the radio is too big to fit though a 5/8” hole and I didn’t want to drill a lager hole in the box. On the other end of the wiring harness I crimped M4 size connectors which goes on to the center two posts of the switch.

The leads form the power supply to the switch I used about a 2-foot length of 12-gauge wire and crimped fork spade crimp connectors on each end. On one end I used the smaller M4 size connectors which goes on to the switch’s terminals and the larger M6 size connectors that go to the power supply. I didn’t put a fuse holder in this length of wire because the power supply has overload protection but I most likely will go back and add an inline fuse holder on the positive wire for added safety.

The GO Box has binding posts to hook up the positive and negative leads form the battery backup to the switch. On the positive lead I put an inline fuse holder and used a 12-gauge crimp butt connector to connect to add some length to the lead. On the negative lead I had to connect 2 pieces of black wire together because I made a mistake and cut it to the wrong length. It almost look like I meant to do that. On each end of the lead for the battery I crimped fork spade connectors, one side has the M4 size that go to the switch and the other side the M6 size that go to terminal posts on the GO Box.

The placement of the wires on the switch is important. The wires going to the radio must be in the center position of the switch.  The wires from the power supply need to go to one end and the wires for the battery to the other end.  All the positive leads need to be on the same row of terminals and the negative on the other set of terminals. I thing the pictures show what I am trying to explain here.

I used an Electrical PVC Junction Box as the housing for the switch box. It also houses the fuse holders of the radio’s power cord and a fuse holder from the battery backup leads.  I wanted to have the fuse holders in the junction box so they wouldn’t get caught up all the other wires that are in the Go Box. The drawback is if a fuse does get blown, I will have to have a screwdriver handy to open the box and some extra fuses.

I drilled a 1/2" hole for the switch to fit in and a 5/8” hole for the wires that go to through. 

I also labeled the hole where the switch is to indicate the weather the switch was set for the Power Supply or Battery. Labeling the box is on of the last things to do but I didn’t wait. 

Next, I put the switch with the wire attached in the PVC Junction Box. I put the switch in the 1/2" hole and positioned it so that when the toggle is in the up position it set to the power supply and the down position to the battery backup. Putting the wires through the 5/8” hole can take a little patience only because with the connectors on the wire you can only get on wire though the hole at a time. The fuse holders are all in the box with the switch.  Then I closed up the box and used the screws that came with it.

Lastly, I mounted the switch box to the Go Box and hooked up the wires to the power supply, the battery binding posts and plug the wiring harness into the radio.