Michael15200
Member
Hey guys, I'm in the middle of tidying up all the shortcuts that the previous owner has made and I noticed there's no circuit breaker or fuse for the battery relocated to the trunk, what sort of fuse rating is everyone using?
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Trunk battery circuit breaker
- Thread starter Michael15200
- Start date
CutlassJim
Well-known member
I have a similar one. Not sure the amperage, either 120 or 200.
CutlassJim
Well-known member
I don't recommend a 100 amp unit.
A lot of people incorrectly think that since the alternator is 90 amp that 100 amp breaker is perfect but that's not how it works.
We've built a starter tester for Borg Warner at my work and under load a starter can draw 800 amps. Hence why batteries have Cold Cranking Amp ratings that high. You get by with 6-8 gauge wire because it's usually such a short amount of time cranking and the wire doesn't have enough time to heat up. But with the battery in the trunk you now have 18 feet of battery cable instead of 3. More resistance = more heat = less power at the unit doing the work (starter).
A lot of people incorrectly think that since the alternator is 90 amp that 100 amp breaker is perfect but that's not how it works.
We've built a starter tester for Borg Warner at my work and under load a starter can draw 800 amps. Hence why batteries have Cold Cranking Amp ratings that high. You get by with 6-8 gauge wire because it's usually such a short amount of time cranking and the wire doesn't have enough time to heat up. But with the battery in the trunk you now have 18 feet of battery cable instead of 3. More resistance = more heat = less power at the unit doing the work (starter).
Agreed. Mine is probably 200. I do know that once on a very cold winter morning with the car sitting outside I did pop the breaker when trying to start the car.
mitsuturbo
Well-known member
I'm running a 200 or 250A breaker. Basically it's just there for if there's a major short circuit in the actual positive cable. Everything else is fused on its own elsewhere.
