I emailed watts24/7 to get their battery cable size recommendation for their 24 volt Growatt unit. I asked about the cable recommendation in their manual and the response was: "1x2AWG. Or 2 x 6AWG is the interpretation." So I assume that means #2AWG battery cable (or 2#6AWG cable.
I was referred to their education information and their calculation for battery cable size goes like this:
"Battery: Use the battery cable suggestion in the manual, keep cables as short as possible, when in doubt choose a thicker cable or double up. Battery Max amps =rated inverter output x 2/ battery voltage, Example 24V, 2.4 KW rated output x 2 /24V= 2400x2/24 =200A."
Will has referred to the chart below for cable sizing and it ultimately is dependent on amps, I assume once the above calculation has been done.
So, in my case, the Big Battery 12V 170 AH LiFePO4 power block would be 24V/170 AH with two in series. The Growatt 24VSPF 3000TL LVM -3KW 120 VAC is rated at 3000 watts. Using the calculation above:
3000 x 2 /24V = 240 amps.
The chart above stops at 200 amps, so the wire size would be greater than 2/0. I think there is something wrong with this calculation, since the manual suggests #2 cable.
The Big battery premade Andersen cables are only 6 AWG, so I would have to make up some big honkin Andersen cables on my own, and I don't know if an Andersen connector for 2/0 wire would fit the Andersen slot on their batteries.
I would prefer a 12V system so that it could be more easily transferred to a future RV application, but these watts24/7 all in one units only go up to 1000 watts in 12V, so I would have to either put at least 2 of their 12V units in series or put 2 batteries in series to get up to 2000 watts, which I think is the minimum inverter load I would need. I think I prefer the simplicity of one inverter, rather than multiple inverters because I think you just double the chance of electronic failures.