Hello, I relocated my battery to my trunk and wanted to ad a circuit breaker just incase the wire ever got cut.

What amperage would I need to buy so that the car would start without tripping the breaker?

 

Starter draw may peak around 400A possibly higher, especially if its a little old, or a little cold out, continous draw while cranking should substantially lower, but the peak is what matters, a 3-400A breaker will let things get mighty hot before it puts a stop to it, also its a failure point and will increase resistance of the circuit. Use quality cable, route the cable smartly, loom it and secure it from rubbing, forget the breaker. If we can put four 1250CCAs in parallel ten feet from the starter in a semi and not burn them down in a million miles you can do it in a 3rd gen, good luck.

 

OK, thanks. I was a bit worried since most stock cars with battery's in the trunk have a breaker. My BMW has one hooked right on the battery post. SO if I did want to install one somewhere around the 300A range would suffice?

 

But is it on the main cable to the starter?
As noted any breaker heavy enough to protect the starter cable is not going to trip on a lighter current short that could burn your car down



Run the cable to the starter terminal , then do your circuit protection after that

 

Yea, the BMW breaker is right on the battery main wire before it runs to the front of the car.

I have it set up like you mention, so I guess I will just leave it as is for now.