RV-8 battery cable size?

[ILikePike]

Trying to figure out the big cables. I have an RV-8 with a rear battery, master contactor on battery tray and starter relay on firewall. I am planning on using 2 awg from the master to starter contactor for voltage drop. Also planning 6 awg for alternator to starter contactor via 60 amp ANL and 6 awg from starter relay to VP-X.
What is the recommended size for:
1. Battery to airframe
2. Battery to master contactor
3. Starter contactor to starter

Could go 2 awg for max power or 6 awg because the runs are short and more flexable to keep pressure off of the battery terminals.

Any thoughts?

[SmilingJack]

I did exactly like you mapped out.

For 1,2 & 3 I used #2AWG

[mannanj]

Originally Posted by SmilingJack

I did exactly like you mapped out.

For 1,2 & 3 I used #2AWG

Ditto above. I would run a second #2 wire for the airframe ground from the negative battery post forward to the firewall. Do not ground the battery locally at the rear battery mount. It will eventually let you down. Ground all your avionics etc. at the firewall terminus of the ground wire run. Some things such as landing lights, nav lights etc. can be locally grounded, but the important things should be grounded at that firewall ground terminal. This will keep radio noise, ground faults and other gremlins at bay.

Be sure to ground your engine crankcase and alternator frame to this same terminal.

[Skyflyer]

I have the same set up as you and used #2 for the long runs from master contactor to starter contactor and the same #2 on up to the starter. I used more flexible #4 for the short battery leads to the master contactor and the airframe ground. The alternator lead is #6. All works well with excellent cranking from an Odyssey 680.

[Toobuilder]

#4 from bat to starter solenoid on firewall - #6 from there to starter. 200HP, no issues.

[vmirv8bldr]

I have the same setup, -8 with rear mounted battery.

#2 Batt to Master contactor, Master Bus, Starter Solenoid, Starter and two ea #2AWG equivalent flexible braided straps for engine ground.

#6 to battery buss
#6 For Alternator to starter solenoid