Growatt SPF-3000TL LVM 24p -- manual recommends 2AWG wire size?

[x98myers7]

hi everyone. I have my Growatt in hand and reviewing the manual. in battery connection section for the 24v model it recommends a single 2AWG wire(38mm2). that seems small to me.

it has a 6kw 5sec burst capability, and 24v 200amp minimum battery capacity. manual says max of 141amps. based on my crappy math we're looking at 6000w/24v=250amp. that's well above the manual recommendations. granted it's only for a short burst, and my T fuse is going to pop at 200, but 2AWG seems small. am I just being paranoid considering it's 3kw/125amp continuous?

I don't want to have to go with 2/0 or larger if i don't have to simply for the cost, but I also don't want to run too small of primary wire. thoughts?

 

[Mattb4]

If they recommend 2awg I am sure that will work so long as the distance to your batteries is short (3ft). The longer the distance the larger of cable you would want to go.

A good reference for inverter wiring is at: https://wagan.com/blogs/news/customer-question-what-cables-do-i-need-for-my-power-inverter

 

[x98myers7]

bluesea has 2awg/120amp on their chart for any distance less than 15ft. i'm using 8ft cables as my battery bank will be on the floor below the Growatt.

 

[Mattb4]

8ft cables would be 16 feet round trip so the recommendation would be for 0 awg (1/0)

 

[agt]

Ref: http://www.paigewire.com/wire_resistance-prop.aspx

My primary concern when choosing cable size is minimizing voltage drop during surges, and minimizing power loss (aka heat) from average current. Both are related to the cables’ resistance.

16 feet of 2awg cable will measure about 3mOhm at 75C ; at 150 amps, I^2R power loss (to heat) would be 66W, IR voltage drop 0.45V.

Switching to 2/0 would halve the resistance and thus both power loss and voltage drop.

The voltage drop probably isn’t consequential.

But if you plan to run your inverter pedal-to-the-metal 3000W all the time, it might be worth investing in the larger cable, or at least give attention to air circulation around smaller cables. 66W is a lot of heat to dissipate.

If your average consumption is a more pedestrian 1000W, power lost drops by (1/3)^2, down to 7.5W with 2awg.

 

[x98myers7]

Thanks, great input.

My average consumption will be very low. Probably will never see 3kw of load. Only 2 freezers and a full size fridge. Max load is going to be startup on the fridge, and maybe defrost cycle. I’ll be monitoring load carefully. I only have a 2kw array in MI, so not a ton of usable power. I’ll plan to upgrade to 2/0 when/if I add another 24v battery.

 

[Xhumeka]

I have the same unit (spf-3000tl 24p) and use 2AWG. I use about 4 feet of cable (8 feet round trip) going to my 860AH FLA battery bank, and even when my jet pump runs for about 10 mins, usually raising the consumption to 2000-2500 watts, there is never any noticeable heat from the cables nor connections.