Wire sizing for battery interconnecting cables - 2/0 or 4/0

Hairfarm

My battery bank will be 12VDC. Six, 6-volt 225ah batteries wired for 12 volts @ 675ah. My inverter is a 2000W Prosine 2.0.

The formula I'm using is 2000w / 12VDC = 166A. 2/0 should be able to handle that. That said, should I use 2/0 or 4/0 for wiring the batteries together? Am I missing something?

FYI, I'll be using 4/0 wire from the battery bank to the inverter.

thanks,

BB.

For one or two parallel strings, I would use full size cable for batteries. For three our more parallel strings you could reduce by 1/2 cross sectional area (+3 awg gauges smaller).

Again, my personal opinion.

Going to fuse each string? (Three or more parallel strings).

-Bill

Hairfarm

Bill, I'll be using three parallel strings.

For three our more parallel strings you could reduce by 1/2 cross sectional area (+3 awg gauges smaller).

Are you saying that 2/0 will be acceptable for three or more parallel strings? Keep in mind you're dealing with first-rate rookie here un-versed in PV vernacular

I hadn't considered fusing the battery cables, but it wouldn't be a bad idea.

BB.

Well--If you want to put me on the hot seat... First the inverter calculation:

• 2,000 Watt continuous * 1/010.5 volts cutoff * 1/0.85 AC Inverter eff * 1.25 NEC derating for wire/breakers = 280 Amp branch circuit rating for full load continuous

Using the NEC table (without the rest of the NEC temperature, conduit fill, etc. derating calculations):

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

Between 250 and 400 cmil wire (or paralleled smaller cables).

If you use marine ratings:

http://www.boatus.com/boattech/articles/choosing-cables-and-terminals.asp

1/0 or 2/0 cable minimum...

So--If you use Marine wiring standards, 2/0 would be OK for main or battery string wiring... You should double check the voltage drop using a voltage drop calculator... Recommend you try for 0.5 volt drop maximum for Inverter and 0.1 to 0.05 for charging.

http://www.calculator.net/voltage-drop-calculator.html

-Bill

Hairfarm

Thanks for your great info Bill. I will keep this in mind when setting up my battery system.

Photowhit

I think in a previous thread you spoke of this.

What might be missing is voltage drop over distance. I believe Prosine will have proper sizing in there manual for different distances. at higher amps voltage drop can be substantial particularly for low voltage systems.

mike95490

Hairfarm wrote: »

......166A. 2/0 should be able to handle that.....,

But can a string of 225A batteries (x3) handle that for very long ? 55A per string ? IF it's evenly split amongst the batteries. More than a couple minutes, and the batteries are going to start to sag under a 50a load.