The Cessna 120-140 Association Forum

would like some thoughts on routing battery cable on a non-electrical 120. previous 120 had the cable run under pilot, thru gear box, under left floor board, up left door post, thru firewall. if one goes this route, start from the front and go to the rear or from the rear and go to the front. has anyone tried going thru the center, under the control cables? if one does the original route, what's the best or good way to get it through the floor board, being it's a 90 degree turn to get up the door post

Hi Ken, It doesn't appear anyone answered your question. The stock routing of the main power cable from the battery follows as such:
1. start at the starter.
2. Back to the firewall with a soft curve to allow for flex.
3. Along the upper third of the firewall over to the large hole on the pilot side(where all the wires run)
4. Along the inside of the boot cowl, straight back to the forward side of the instrument panel.
5. Down the forward side of the door post to about.
6. Mid/upper span of the forward gear box bulkhead, then straight towards the center of the aircraft.
7. A little past the steel left gear box inboard edge, the wire makes a 90 degree turn and goes directly aft.
NOTE:. "For your question below" Stock aircraft ran the wire under the pilots floor board in this area. With this arrangement it's impossible to access the wire if needed without un-riveting the floor board. When I re-do aircraft, I run the wire above the floorboard, but tight to the forward edge of the gear box bulkhead and secure with adel clamps. (#6 & $7 above)
8. Ok, we're routing straight aft, through a set of grommets for the forward and aft gear bulkhead, the wire runs under the seat pan and baggage compartment. I prefer to use airline routing and run the power wires as high as possible, (so that nothing drips or snags on them) so I've attached the wire to the seat pan and baggage compartment skins with adel clamps. then a grommet through the aft baggage compartment bulkhead, and up to the battery master contactor on the back of the battery box.
9. I don't see any possible advantage to running the cable down the center, in fact I would estimate it to be more difficult.
I trust this is what you're looking for?

thanks, i'm using an odyssey battery, and to balance the starter/battery, i've got the spring seats, so will look at putting the battery under the pilot seat. i like that going along the gear box instead of going under the floor board. thanks again

Ken, Please re-read my post, I see you responded while I was re-typing portions of it.

thanks vic, if i go under the seat for the battery and i haven't had time to measure the length of the cable needed (light weight starter), can one go with 8 ga. wire or need to go bigger

VIP620 wrote: ↑Sat Apr 25, 2020 11:51 amcan one go with 8 ga. wire or need to go bigger

You need to know the current draw of the starter. Then, use the chart in figure 11-3 in AC43.13. You can find the max length for a #8 wire, or the minimum size regardless of length.

For starters (no pun intended), a #8 wire is good for a maximum intermittent load of 70 amps up to 20 feet in a 14 volt system.

For starters (no pun intended),

That's talent there!!!

VIP620 wrote: ↑Sat Apr 25, 2020 11:51 am thanks vic, if i go under the seat for the battery and i haven't had time to measure the length of the cable needed (light weight starter), can one go with 8 ga. wire or need to go bigger

Pretty certain you'll need larger wire.............check the wiring charts as John stated.