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Multi-purposing an ANL fuse

cdeerinck

Well Known Member
My primary Alternator is rated at 60 amps, and my back up is rated at 40.
Only one can ever generate current at a time (they are on a shared toggle).

Is there any reason not to run both of them through a single 60 amp ANL fuse for over-current protection, as opposed to running one through a 60 amp fuse, and the other through a 40 amp fuse?

They will both have to go through a Dynon Ammeter Shunt later, so it seems to me there would be no reason to keep them separate before then.

I guess another way to ask the question would be: Is there any problem with running a 40 amp alternator through a 60 amp ANL fuse?
 
If the 60 amp alternator takes out the ANL then the 40 amp alternator is irrelevant, you have no alternator in this scenario
 
Theory

In theory the fuse protects the wiring not the alternator. So a 60 amp fuse should be fine for the 40 amp alternator if the wiring is 60 a rated. However you may want to think about not running a single fuse. The only time I blew the alt fuse in a spam can wAs when the alternator developed an internal short and the battery supplied the current to blow the fuse. So need to consider the reason for the fuse.
 
What John said. But if you're trying to keep the firewall clean, have you considered a fusible link? Link wire is purpose-built for the application, with fire proof insulation. Fairly common in cars, and eliminates the need for any kind of fuse holder. You just buy the link wire 4 sizes smaller than the wire you're protecting. Joint can be soldered & heat shrunk, or mated with a PIDG butt splice crimp. Links are typically ~4"-6" long, and there's no fuse holder at all.

Charlie
 
Very good ideas

Thanks, guys, two very good points you made.

1) I am electrically dependent, so I will definitely not go through a single point.
2) I will check out the fusible link, and run two of them.

As usual, I really appreciate the help. Building solo in my garage makes asking for opinions difficult without VAF.
 
If you do go the link route, just mark the wire run well as to where this fusible like is, theses become non apparent if they are burnt when troubleshooting a problem. I am using 3 ANL fuses, ALT feed, main feed and back up battery feed.
 
Marking everything (including the gauge of the link) is great advice, but there should be no doubt as to the link's location. Its duty is to protect the B lead wire, so it should be where ever the B lead attaches to the electrical system. That would typically be the master contactor, or if the battery is in the rear, the supply side of the starter contactor. Basically, a ring terminal on that end, and either a butt splice or solder/heat shrink to the start of the heavier B lead. Solder requires a bit more skill; the butt splice will likely require 'fattening up' the wire in the link side of the splice (unless you search out an asymmetrical splice). All are detailed in the Aeroelectric book.

Charlie
 
Littelfuse MIDI

I used one of these guys inline:

https://www.littelfuse.com/products...mercial-vehicle-fuse-holders/midi-498-il.aspx

inline_midi_holder.jpg
 
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