fuse alternator wire

[Steve Hansen]

Our alternator charging wire on Georgia Peach is a direct connection from alternator to main house bank. I wish to fuse this and reviewed Jim Moes schematic. http://www.c34.org/projects/images/CatalinaElectricalschematic.pdf I see he has fused the wire close to the battery. I was reading Nigel Calders electrical text and it said the fusing should be close the the power source i.e. 7 inches and that technically the alternator is the power source. I was wondering if anyone has fused this circuit in the engine compartment near the alternator?

[Ron Hill]

Steve : I believe you need to reread, as the item that's being charged is the item that needs the fuse protection.   

[Stu Jackson]

Fuses can be installed in or near the battery box, where they should be located.  7 inches is pushing it, although I do not disagree with Calder, but he can sometimes be misleading.

The simple answer is:  put a fuse in your alternator output as close to the bank as you can, rather than in the engine compartment near the alternator.

We have the fuses for our sources as (combiner, charger output and alternator output) in the battery box.  Ours are MEGA fuses.  Some other skippers use circuit breakers.

[Ray & Sandy Erps]

Fuses protect small wires from burning should a short occur.  The fuse should be located as close to the current source as possible.  In the case of the alternator charging wire, you have a current source at each end.  The alternator end can put out 50 to 100 amps, your battery bank can put out a couple of hundred amps depending on the size of your bank.  If you sized your output wire to handle the alternator output, what you're protecting it from is the potential amperage in the battery bank in case there was a short.  I agree with Stu and Ron that it should be close to the battery bank, where the big amps are. 

[Steve Hansen]

Ray
I see the logic in what you are saying, the battery bank can put out a lot more amps in a short than my 50 amp motorola alternator, therefore fuse the wire close to the bank. Calders book does say something about fusing near the power source i.e. alternator with the exception of "self limiting devices" such as an alternator with internal regulation and "arguably" alternator with an external regulator. p190 under charging devises for anyone interested. I'm satisfied with everyones advice and fused the wire in the battery compartment. Thanks much-Steve