how many AWG should the cable be between the lifepo4 battery and the inverter?

mahdi89

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how many AWG should the cable be between the lifepo4 battery and the inverter? 5KW(120Amax imput/output)
distance 5ft(1.5meter)
 

kuranaga

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1.5m is already very long. I would see if you can shorten that to 50-60cm, move the batteries etc. Then take #2 wire and you will be OK
 

FilterGuy

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Here is how I do it.

I will assume 90% efficiency on the inverter.

the inverter needs to draw 5000/.9W = 5,556w from the battery.

On a system that size, I will assume 48V battery.

The most current will be when the battery is low, so the current will be 5556W/48V=116A (The 120A mentioned in the post sounds about right)

I then look at the top line of the Blue Sea Ampacity Chart. For 120A you will need 2AWG marine grade.

NOTE: Marine grade wire has a relatively high temp rating. Other wire types with lower temp ratings will require larger wire.
 

mahdi89

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Here is how I do it.

I will assume 90% efficiency on the inverter.

the inverter needs to draw 5000/.9W = 5,556w from the battery.

On a system that size, I will assume 48V battery.

The most current will be when the battery is low, so the current will be 5556W/48V=116A (The 120A mentioned in the post sounds about right)

I then look at the top line of the Blue Sea Ampacity Chart. For 120A you will need 2AWG marine grade.

NOTE: Marine grade wire has a relatively high temp rating. Other wire types with lower temp ratings will require larger wire.
even if it was long like 5 feet ?
 

FilterGuy

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even if it was long like 5 feet ?


The Blue Sea chart has info on selecting wire based on % voltage drop. However there are a couple important aspects to remember when using the chart.

1) The distance is round trip. If the battery is 5 feet from the inverter, the round trip is 10Ft
2) The chart is based on 12V systems. For a 24V system, cut the round trip in half. For a 48V system, use 1/4 the round trip.

In your case, I will assume it is a 10ft round trip but for 48V I will use 10/4= 2.5ft According to the chart, 2AWG is fine.
 

Scph9002

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I have a lot of spare bus bars so i use these as conductor instead of wire. Fits perfect on my inverters terminals and 2x bus bars are equivalent to 80mm2 or between 2/0 awg and 3/0 awg wire. Negligible voltage drop but a little risky with exposed conductors. :))
 

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kuranaga

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I have a lot of spare bus bars so i use these as conductor instead of wire. Fits perfect on my inverters terminals and 2x bus bars are equivalent to 80mm2 or between 2/0 awg and 3/0 awg wire. Negligible voltage drop but a little risky with exposed conductors. :))
you don't get better crossection with these bus bars! a solid #2 or #0 has same or bigger cross section than your bus bars
 

Scph9002

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you don't get better crossection with these bus bars! a solid #2 or #0 has same or bigger cross section than your bus bars
busbar are 2mm x 20mm and there is 2 of them in paralell. 4mm x 20mm is not 80mm2? XD
80mm2 is thicker than 2/0awg
 

smoothJoey

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busbar are 2mm x 20mm and there is 2 of them in paralell. 4mm x 20mm is not 80mm2? XD
80mm2 is thicker than 2/0awg
Plus the busbar has more surface area and no insulation so it should dissipate heat better.
The OP really should put some shrink tube on those bars though.
 

Hedges

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Plus the busbar has more surface area and no insulation so it should dissipate heat better.
The OP really should put some shrink tube on those bars though.

It would be a royal pain to slip tubing over it after bolting/mounting.
I suggest my split heater hose approach; that can be retrofit in place.
Would be nice to have something perforated to preserve the air circulation, though.

img_20211002_131808-jpg.67201


Couple problems I do see:
Moisture in particle board becomes a conductive path. Proper insulators aren't hydroscopic.
Whatever temperature rise they do have is applied to sawdust.
 

Scph9002

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Plus the busbar has more surface area and no insulation so it should dissipate heat better.
The OP really should put some shrink tube on those bars though.
I got some really wide heatshrink i intend to insulate the positive busbar. Should be "safe enough" I dont see much purpose of insulating negative bus bar though considering earth ground, ssc/inverter chassi grounds and AC ground are bonded together anyway and are huge surface areas with a return path to battery main negative
 

740GLE

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The cable sellers don’t approve of you’re set up, they want you to buy 2/0 or even better 4/0, and buy lots of it!
 
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