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Old 11-29-2012, 06:49 PM
ILikePike ILikePike is offline
Join Date: Jan 2011
Location: Eatonton, GA
Posts: 216
Default RV-8 battery cable size?

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?
Jeff Green
2016 RV-8 #82985
1968 E33C Aerobatic Bonanza
Pleased to donate Dec 2019
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Old 11-29-2012, 06:59 PM
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SmilingJack SmilingJack is offline
Join Date: Dec 2010
Location: Hilton Head Island
Posts: 1,105

I did exactly like you mapped out.

For 1,2 & 3 I used #2AWG
John Mastro
10 years of Awesomeness!
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Old 11-29-2012, 08:25 PM
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mannanj mannanj is offline
Join Date: Jan 2005
Location: Mtns of N.E. Georgia
Posts: 1,322
Default Wire size

Originally Posted by SmilingJack View Post
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.
Mannan J.Thomason, MSGT. USAF (RET)
"Bucket List" checkoff in progress!
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Old 11-29-2012, 08:29 PM
Skyflyer Skyflyer is offline
Join Date: Mar 2007
Location: Sugar Land, TX
Posts: 144
Default 2 & 4 AWG

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.
Chuck McCluggage
Sugar Land, TX
RV-8 IO-375 WW 200RV
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Old 11-30-2012, 08:51 AM
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Toobuilder Toobuilder is offline
Join Date: Jul 2009
Location: Mojave
Posts: 4,789

#4 from bat to starter solenoid on firewall - #6 from there to starter. 200HP, no issues.
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C
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Old 11-30-2012, 07:31 PM
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vmirv8bldr vmirv8bldr is offline
Join Date: Jun 2005
Location: Eastvale, CA
Posts: 378
Default Similar

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
Bart Filipiak
Eastvale, CA
RV-8 N74VB

Barrett IO-390
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