Good info. That's a reasonable size...
Keep in mind that its 130A is probably at a highish RPM - ie, not at idle to 3,000 RPM.
130A @ 13.8V implies ~1800W (or ~1870 at 14.4V) as a maximum load without discharging the battery.
It would probably handle a 1000W continuous load assuming normal driving (not too much stop-start at idle).
But that includes engine and lights and stereo & & & ....
Yet again the best "monitor" is a voltmeter across
the battery for SOC (State Of Charge) of the battery.
But remember that SOC is an OPEN circuit measurement (no load; no charging) with surface charge removed. (Eg ~11.4V is probably 100% discharged (and damaged!); ~12.7V is fully charged; and anything up up to ~13.7V with surface charge.)
And even if fully discharged, an alternator will usually bring the voltage up to normal (somewhere between 13.8 & 14.4V).
And of course there are 2 batteries (ie, 2 voltmeters, or a battery selector switch?).
If you mentioned the alternator rating to help size the interconnect - it doesn't.
It is (1) the
equipment load (meaning accessories, attachments etc) PLUS (2) the battery recharging load that determines that.
If that figure gets too high (for economical or reasonable design), then an average figure could be used rounded up to the next relay/fuse size.
EG - if coffee maker is max load and is 1,000W, and battery might take 70A if reasonable discharged...
1000W/13.8V = 72A + 70A battery = 142A = (say) 150A relay/isolator/fuse/cable. Maybe 200A isolator; 300A cable and 150A fuse in practice.
But if its 1000W @ 12V (not charging; and the coffee maker is a constant power load), then 1000W/12V = 83A compared to its 72A @ 13.8V.
But the battery won't be charging, hence 83A total, not (72A+70A) nor (83A+70A). Cool!
Let's say a 150A relay etc is too expensive.
Or we realise that is overkill. IE - coffee whilst stationary (not charging, hence 80-90A) and the biggest "in motion" load is DVD/TV at say 200W - ie about 20A.
Hence we decide a 100A relay/isolator is adequate.
100A handles the 1000W "constant power" coffee maker. (1000W/100A = 10V; ie, handles the 100A that the 1000W coffee maker takes if it was getting 10V (maybe due to a 1V drop between it and the front 11.0V battery).
100A also handles the 20A DVD/TV and the 70A "maximum" rear battery recharge current (if using whilst charging).
If the 100A is exceeded, then the interconnect fuses will blow - maybe never for 110A, maybe after 15 minutes for 120A, and maybe after 60 seconds at 150A etc.
That's annoying if it's a temporary problem. (EG - excessively discharge battery is taking 120A, or we started the engine whilst running the coffee maker (142A etc).)
That's when either a fuse-blown alarm is handy, else self-resetting circuit breakers. (I use the latter. Assuming the load is reasonably less than the circuit breaker rating, in practice the battery will usually charge more than discharge, hence battery recharge current decreases each time the breakers reconnect. Just make sure breakers fail properly rather than melt or explode!)
But that'll do for now. The above gives some considerations or situations - though in some cases no rear battery (to contribute power) is considered.