Advice on fusible link

Howard Jones

Supporter
So I am finishing up a draft electrical drawing , buying gauges and other electrical pieces, and generally getting ready to wire my SLC. I would say that the drawing and component selection is 90% complete but I do have one question for the group.

All my other loads circuits, pumps, fans, lights etc. are going to be protected with circuit breakers instead of fuses, but I haven't really settled on the alternator charging circuit. Most cars nowadays use a fusible link. This is really a short piece of smaller gauge wire in series with the larger wire that is the path from the alternator to the battery. Their main advantage is they can survive short duration high current conditions that would otherwise cause a fuse to blow but will melt open if the high current lasts too long and would otherwise burn up the wire harness.

I am considering using a circuit breaker in the alternator circuit also but am wondering what others have used or if other kit car type systems use anything at all. My GTD doesn't protect the alternator circuit at all, for example. I've seen wire harness kits that don't address this issue at all either. I've never seen anything on a race car at all in the alternator circuit for protection.

What do you guys think about these? A little expensive but they look very robust and can be manually reset.

Resettable Circuit Breaker Cooper Bussmann

Or am I just getting too deep into this and worrying for worry sake? What do you guys think?
 
Last edited:

Dimi Terleckyj

Lifetime Supporter
Hi Howard

Simple, a fusible link will leave you stranded if it blows but a resettable circuit breaker can be reset and you can continue.

My choice in my 40 was for breakers.

Dimi
 
As you say most don't protect the alternator in kit cars but I'd go with what the OEM's do and protect it with at least a fusible link.

Charging_Circuit.jpg


If you make the fusible link separate from the rest of the power then you will be able to still drive it until the battery runs flat (just make sure you have a 'charging' warning light so you know!)

One thing worthy of mentioning is to even if you have circuit breakers still to use an in-line mega-fuse (or similar) immediately after the battery to protect everything even the worst case scenario of a short circuit before the circuit breakers.
 

Howard Jones

Supporter
Very good stuff, thanks. My thinking is since I will have a main power switch directly in line with the pos. terminal of the battery then the battery can be switched off completely with it.

Then each leg of the load series can be protected with a appropriate sized circuit breaker. I think I will add a 100 amp circuit breaker in the alternator circuit also. At this point in the build it is a easy thing to do.

Lastly since this is a track car I am really dedicated to reliability. Track days are expensive and even a delay for repairs of a few hours can eat up hundreds of dollars in expenses by working on the car instead of running laps. Also I like the idea of being able to limp back to the pit lane on the battery if the alternator should fail.

Good discussion. Thanks again. Sometimes we just need conformation.
 
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