car startup fuse rating to use?

[onosqv]

Helllo, Well, my 60 amp agu fuse was no good - blew the fuse as soon as I try to start the car.

I've basically isolated my sound system to the aux battery. Everything else goes to the main battery.

Currently using 140 amp circuit breaker for aux stuff. What should I use for my main battery (connected to starter)?

[Simmsled]

What is connected to what in your system?

[onosqv]

Starter & stock things, whatever is normally connected to the regular battery (i.e. ecu, headlights, signals, fuse box stuff).

All audio and such are connected to the 2nd battery.

Thanks.