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Both of my planes have the battery located behind the rear seats, with long wire runs and no protection. The relays are mounted close to the battery boxes and both have aluminum fuselages so that the potential for shorting of the positive lead is much greater than on a composite fuselage.
In the Navion for example, North American used #2 battery wires (14V system). The next largest wires are #10 (charging circuit) and the vast majority of the wiring is #18. It seems to me that everything else would burn out before the battery wires. Lancair wisely doesn't spec wire sizes but I imagine a typical system would have similar size relationships.
In a composite fuselage there is a need to run two heavy-gauge battery wires, one for positive and one for ground. The Velocity had the battery location in the nose for W&B so both cables had to be sized to carry 14V starter current the full length of the fuselage. That's an extreme but it shows what can be done.
The only way the battery cables could get fried in a composite fuselage would be for them to short together and it shouldn't be difficult to provide adequate separation. I've heard much mention of failure points before and I suspect that putting a fuse into the system would create several. Although I'm years away from this issue I think the only drawback to a remote location is the extra weight of the longer cables and perhaps W&B oncerns. -Bill Wade
----- Original Message ----- From: "Colyn Case at earthlink" <colyncase@earthlink.net>
To: <lml@lancaironline.net>
Sent: Sunday, November 01, 2009 7:01 PM
Subject: [LML] Re: L-IVP Battery Cooling
Bill,
I just looked at that too.
My conclusion was that fusing the starter was possible but difficult (takes
an expensive and very large cooper-bussman very slow-blow fuse).
But fusing the main battery bus (the part that starter current doesn't go
through) is very doable with an ANL.
I don't know if that helps your situation. If your whole power grid is in
the back it won't. but if the rest of it is up front, it would help protect
those long wires against anythong other than the starter misbehaving.
ANL data-sheet attached.
Colyn
----- Original Message ----- From: "billhogarty" <billhogarty@hughes.net>
To: <lml@lancaironline.net>
Sent: Saturday, October 31, 2009 4:17 PM
Subject: [LML] L-IVP Battery Cooling
Ralf:
I also have the A/C compressor option that required me to move the
battery. I looked at mounting it above the turbo controller but was
afraid of cooking the battery so I just moved it to the luggage
compartment.
I also moved the master relay and mounted it right on the battery box. I
did considered fusing the longer battery cable but decided against it. I
think that Honda tried a battery fuse years ago with poor results.
Anyway, no problems so far.
Regards, Bill Hogarty
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