Electrical System

I had resisted installing an electrical system in the Cub, operating with just a Icom handheld and a Garmin GPS III . After my cross country to North Carolina last month it was clear this would not be acceptable for the long trip to Oshkosh.  I found a really nice 3.4 AH sealed lead acid battery at Aircraft Spruce and I built a battery rack for it that fits just behind the seat. If this works out , I will use the same mount when I install the larger battery for the starter. I formed the rack from 0.032 aluminum with 0.750 flanged edges. I installed some angle for the forward and aft stops, and made a hinged strap from 0.032 for a hold down clamp. To make it easy to install the clamps they are installed first using AN 315 nuts then the rack is installed with AN 365 nuts. This saves a lot of fighting with the Adel clamps. Here are the clamps installed.

 
This is just behind the seat, you can see the elevator bell crank on the right. Here is a shot of the rack installed.

 
Here you can see the details of the rack. It's a bent up aluminum channel with fore and aft stops riveted on. The strap is hinged at the left and it's secured with a single AN 525 screw at the right. There is a nut plate riveted underneath. The battery weighs 3 lbs and the rack less than 1 lb. I think this same rack could be scaled up just a little to fit the PC 680 battery if I install the starter.
 I was tired of having the radio beside the seat so I made an angled mount up by the mag switch. Here is a picture of it.

This Icom A6 radio has no good mounting provisions, so I had to make my own bracket. The angle bracket I formed from 0.025 and it angles the radio so the screen can be seen from the back seat. The bracket attached to the radio is from 0.020 aluminum. It screws to the back of the radio where the Icom belt clip is installed. It clips over the top of the airframe angle bracket and then is held in place with a strip of 2 inch wide Velcro.  So far this works OK but it's a little hard to read the screen.
I made this bracket to hold the GPS.

It's just a formed channel held on each end by an Adel clamp. It is up on the cabin roof  just below the sky light. I have to look out the top of my glasses to see it . The Cub is so slow I usually just use it to get a compass heading then turn it off for 10-15 minutes.  You can see the red Icom push to talk switch, I have removed that and have it on the stick now.
The real problem is that every device runs at a different voltage, the radio at 11 volts, the GPS will take 12 volts and the headset needs 9 volts. I ended up using this 3 unit cigarette lighter plug I bought at Walmart.

It has nice little on off switches and had really nice LED lights but they sucked about 12 ma each so I had to disable them. Just behind the ELT you can see the voltage converter / filter for the headset. It drops the voltage to 9 volts for the noise cancelling headset. I know this looks a little cheesy but it was the easiest way to get a switch and fuse for each circuit. Here are some shots of the wiring, it looks like a mess but it's out of the way and is much better than what I had before.

I did some testing and the radio draws about 238 ma when receiving and 970 ma when transmitting. The radio still has it's internal Li ion battery as a back up and recharges from the lead acid cell at about 175 ma with the radio off. The GPS draws about 70 ma and the noise cancelling headset draws 11 ma. With everything on I should be good for about 6 hours, much longer with the radio off.
I'm still working on the antenna installation, more on the later.