Cable to inverter from battery rack confusion

[wildbillpdx]

I'm trying to wrap my head around the calculations for what size cable I need running from my battery rack to the my inverter. I have an EG4 6000EX which is rated at 6000 watts. I have three EG4 LifePower4 48 volt batteries. Reading online the calculation for cable size seems to be maximum watts (6000) divided by battery voltage (48) which gives me 125 amps. With that calculation various tables show I should use 4 awg cable for 6.3 ft. or 2 awg for 9.9 ft.

Is this calculation correct? The batteries have a 100 amp discharge rate. Reading about series and parallel (the batteries will be parallel) says you combine the amps which would be 300 amps for three batteries. If this is the calculation then it's 2/0 awg for 10 ft.

I'm confused.

 

[42OhmsPA]

It is very confusing until it makes sense, I'm starting to get there.

Size for the worst case scenario... That inverter can actually supply 12,000+ watts during a surge. 12,000w / 48v = 250a.

Here's a sub optimal example.... I'm running the same inverter for this scenario except mine is blue...
Earlier my well pump kicked on, my 1st BMS picked up a 74a draw, the 2nd was very close to that but I didn't get a reading. (2 16s 230ah diy packs) We'll use 140a and 53v for easy numbers; 7,420 watts. Unfortunately the Voltronic inverters and solar assistant sampling rate aren't fast enough to catch this spike... I'm using 1AWG marine wiring, if I were using 1/0 or 2/0 I suspect the voltage drop wouldn't have been as bad.

I hope that helps and doesn't confuse you further.

You could use a smaller wire size to parallel your packs to the buss bars then larger from the buss to the inverter.

I'd also add at least 1 Class T fuse before the inverter, ideally 1 for each battery.

 

[wildbillpdx]

You could use a smaller wire size to parallel your packs to the buss bars then larger from the buss to the inverter.

That's actually the plan. I just received the bus bars today, hence the calculation. I need to build cables from the batteries to the bus bar and bus bar to inverter. Still trying to identify the lug sizes needed as well as cabling.

 

[42OhmsPA]

If you are building your own I can recommend the store below for quality cable, lugs and heat shrink. I've made 2 orders and I'll be making a 3rd soon enough.
There are other quality recommendations on the forum as well (it's where I found Greg's)

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