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Battery Cable Size to Combiner

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Kemmer

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Looking for some help sizing our cables.

We ordered 3 48v 200ah LifePO4 batteries. They came with 35mm2 (2awg) EVR cables

We plan on having them tie into the manufacture supplied battery combiner box. The box (attached) has 125A breakers with 6awg jumpers going to the combiner plate.

From the combiner plate, they provided 35mm2 (2awg) EV cables to connect to the inverter.

Do all these gauges seem correct? The 6awg jumpers seem small.
 

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If insulation temp rating is high enough, then yes it can handle 125 amps.

This is my favorite ampacity chart

What is wire ampacity and how do you find ampacity rating?

When selecting a cable, one must know its wire ampacity rating. This rating has been determined by the NEC (National Electrical Code)..
www.wireandcabletips.com www.wireandcabletips.com

A better question is what is your max kW draw, and do you want to plan to use one or two batteries if a one oe two go down.
 
chrisski said:
If insulation temp rating is high enough, then yes it can handle 125 amps.

This is my favorite ampacity chart

What is wire ampacity and how do you find ampacity rating?

When selecting a cable, one must know its wire ampacity rating. This rating has been determined by the NEC (National Electrical Code)..
www.wireandcabletips.com www.wireandcabletips.com

A better question is what is your max kW draw, and do you want to plan to use one or two batteries if a one oe two go down.
Click to expand...
Thanks. The battery cables are listed at 125*C.

Regarding the draw, I'm looking at our invert cutsheet and not sure where I can locate that information. We have the Megarevo R10KLNA. The max charge/discharge rate is 210 amps. The battery voltage range is 40-58 with a max charge voltage of 58v.

In the combiner, it looks like the 6awg is rated for 200*C.
 
Kemmer said:
Regarding the draw, I'm looking at our invert cutsheet and not sure where I can locate that information.
Click to expand...
For the inverter, Amp draw = inverter wattage / low voltage cutoff / efficiency * 1.25 safety factor

Example a 6000 watt inverter that is 85% efficient on a 48 volt system with a 40 volt cutoff

220 amps = 6000 / 40 / .85 * 1.25

That 220 amps would be distributed between the three batteries, so less than rated on each. Two should be OK, but definitely not one.
 
chrisski said:
For the inverter, Amp draw = inverter wattage / low voltage cutoff / efficiency * 1.25 safety factor

Example a 6000 watt inverter that is 85% efficient on a 48 volt system with a 40 volt cutoff

220 amps = 6000 / 40 / .85 * 1.25

That 220 amps would be distributed between the three batteries, so less than rated on each. Two should be OK, but definitely not one.
Click to expand...
Thanks. So we have:
10,000w inverter / 41V battery cut off / 97% Efficiency * 1.25 = 314 ~ 320 amps

Should any of the cabling be upsized? The combiner jumpers? Combiner to inverter?
 
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