Being a fiberglass plane running the cable directly from the battery to the buss would not be unreasonable.  Just make sure that the cable is large enough to carry the calculated load plus.  If you want to protect the wiring from the battery to the buss place a fuse or CB close to the buss.  Being a fiber glass plane there should not be any opportunity for the cable to short to ground unless you are running the neutral or some other wire in the same raceway as the positive cable.

Bob Perkinson

-------------- Original message from "Mark Steitle" <msteitle@gmail.com>: --------------

So, what's the most reliable method of getting the big fat wire from the battery (in the tail) to the essential bus at the panel?  I had initially connected this wire directly to the battery (unfused), but later added the big 60 amp fuse.  Being a fiberglass plane, would a carefully run unfused wire be preferrable to a fused wire?  Is a relay more reliable than a big fuse?  Would a solid-state relay be even better? 

 

Mark S.

 

On 12/4/07, Al Gietzen <ALVentures@cox.net> wrote:

 

That's what I did... Flight Critical bus is always hot, although I did add a 60 amp fuse back near the battery. 
 Mark S.

Is that fuse in the only power path to the engine critical bus?  I think fuses are a very reliable way to go; but for this application they are synonymous with "fault tolerance".  IOW, blowing one fuse does not shut you down.  Actually, I would also apply the fault tolerance idea to the use of breakers for critical items.

One of the nice things about our setup is we have dual plugs, dual injectors, dual controllers, and dual fuel pump. That gives you the potential for very high reliability - a failure of any one of the pair does not put you on the ground.  I chose to use a separate circuit to each to gain failure tolerance. Each circuit is protected with a fuse, and the fuse holder is powered directly from both batteries with isolation diodes so even a battery failure doesn't stop the engine.

Wires are cheap and light and very reliable. Fuses cost only pennies, so change them out and check the contacts every annual, or every 6 months if you feel like it. I like that better than a breaker that has been in the panel for 10 years. Fault tolerance = high reliability. (I almost said – fuses and fault tolerance, but I don't want to start that fuses vs breakers discussion again J )

FWIW,

Al