battmann

iTrader: (9)

I relocated my battery to the hatch during my LS swap and everything was working fine but am now trying to add some circuit breakers so everything is protected. Below is a diagram of what I’m trying to do.



The 0ga wire to the starter is only powered during cranking.
The 6ga wire pretty much powers all of the car: factory fuse box, radiator fans, etc
The 4ga wire is for the alternator to charge the battery. Nothing else is connected to this electrical path. I’d like to install a circuit breaker to protect this wire but am not sure which side would be considered IN. Would this be the wire coming from the alternator or the wire coming from the battery? Here’s the circuit breaker I plan to use.

OrangeBird

iTrader: (1)

An interesting question......

In normal operation, of course since the alternator is the power source here, it should be the IN, and the battery, as the receiver of the generated power, should be the OUT.

BUT!

The most common failure mode we're trying to protect from here obviously would be a short circuit, either in the wiring or perhaps the diodes in the alternator, which would then indeed make the battery the source of the circuit's power, and not the alternator.

Given that current flow is equal in all parts of a circuit, I'll bet it'd trip either way (shorted alternator drawing mad current from the battery, or shorted battery causing the alternator to push mad current the battery's way) provided the circuit is able to deliver current above the breaker's rating.......

vorteciroc

In these configurations the Fuses or Breakers are going to protect the Cables from a Short to Ground.

We need the approximate Cable lengths...
Then an Ampacity Chart can be used to determine the Maximum Continuous Amperage that each Cable can support as it's own Circuit.

Then you can Fuse accordingly.

QwkTrip

iTrader: (22)

Just a note on starter motor cable sizing...

Starter cable is the one cable not sized according to continuous current rating. (Cables would be overly huge if done that way)
Instead, the cranking circuit is sized to manage voltage losses so the starter performs to expectation. Starter will be sluggish if too much voltage drop in cables & connections.

SAE J3053 gives guidance of battery cable sizing for starter motors. For 12V starters in range of 0.5-2.5 kW output, recommendation is to limit voltage losses to maximum (0.3V per 100 Amp). This equates to maximum 0.003 Ohm circuit resistance (all cables and connections from battery B+ to battery B-).

battmann

iTrader: (9)

the battery relocation was a kit from Flaming River. it was this one which now looks to be discontinued. the only modification I made was to include a Ford solenoid so this wire is only powered when cranking.
https://www.summitracing.com/parts/fla-fr1060

i took some rough measurements on cable lengths:
4ga from battery to alternator = approx. 23'
6ga from battery to fuse block on firewall = approx. 20'

i finished my Terminator X Max install and fired the car for the first time this past week (it's an LQ4 turbo engine). it looks like my alternator isn't charging the battery. i'm not sure if it's the wiring or the alternator. i had a FITech system running my engine last summer and everything worked fine.
over the winter the seal between my PS reservoir and pump failed and leaked fluid into the alternator. i caught that before starting the engine. i didn't want to spray any cleaner in the alternator so i removed the alternator and tried letting the fluid drain out. the alternator is a TuffStuff 175A unit (8242NB). i took the alternator to two different parts stores yesterday to have it tested and both said they can't do it unless it's in the car. i don't trust driving the car that far and you can't really access the alternator with all the turbo piping anyway.
i am using Holley's LS pigtail (197-400). the L terminal wire has a resistor and is connected to an IGN port on my factory fuse block. i added a wire to the S terminal and connected it to the main distribution block on my firewall.
battery is an Odyssey AGM75 86 which was bought brand new July 2023. battery has been on an AGM tender over the winter.