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stock BMS wire undersized?

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moonlight23

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Aug 8, 2022
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I have a JBD 100A BMS with two 10awg size wire per terminal. I feel like JBD knows what they're doing, but two 10awg feels undersized. I don't feel comfortable potentially running 100A through these stock wires.

Should I leave it or try to replace the wires with two 8awg wires?
 
I had similar thoughts about my JBD wires last year - see my thread here and the responses

diysolarforum.com

Are equipment-supplied cables really big enough for 100A?

Have just upgraded to a larger inverter that will now handle 100A (48V system). Have upgraded fuses and DC cables as far as possible - we now have 40mm2 cables to support the new load. But, at either end of my 40mm2 cables, I am left with... - the supplied Solis DC cables with Amphenol...
diysolarforum.com diysolarforum.com
 
There's almost no current going through those wires , other than passive balancing.
They are mainly used for voltage sensing I would expect
 
houseofancients said:
There's almost no current going through those wires , other than passive balancing.
They are mainly used for voltage sensing I would expect
Click to expand...
It's the main wires, on the C- and B- terminals, not the tiny balancing/sensing wires.

10awg for balancing wires would be completely unnecessary lol
 
SeaGal said:
I had similar thoughts about my JBD wires last year - see my thread here and the responses

diysolarforum.com

Are equipment-supplied cables really big enough for 100A?

Have just upgraded to a larger inverter that will now handle 100A (48V system). Have upgraded fuses and DC cables as far as possible - we now have 40mm2 cables to support the new load. But, at either end of my 40mm2 cables, I am left with... - the supplied Solis DC cables with Amphenol...
diysolarforum.com diysolarforum.com
Click to expand...
Brett V said:
They are silicone 8 ga wires, ultra fine strand.
Click to expand...

Your guys' 100A BMS looks like two 8awg wires, which would be fine and what I want to replace it with. The ones on mine is only 10awg, not 8awg.
 
Just for clarity:
20240509_175751.jpg

It looks like the insulation is indeed silicone rated for 200C which is good. But I thought temperature protection is separate than the actual current carry capacity, which is what affects resistant and voltage drop, and this depends on the cross section size of the conductor.
 
moonlight23 said:
Just for clarity:
View attachment 214342

It looks like the insulation is indeed silicone rated for 200C which is good. But I thought temperature protection is separate than the actual current carry capacity, which is what affects resistant and voltage drop, and this depends on the cross section size of the conductor.
Click to expand...


The copper in wire can carry absurd amounts of current. It's the temperature rating of the insulation that limits current. Your insulation can't catch fire.

One 10awg fine strand 200°C wire is good for 70A.
 
sunshine_eggo said:
The copper in wire can carry absurd amounts of current. It's the temperature rating of the insulation that limits current. Your insulation can't catch fire.

One 10awg fine strand 200°C wire is good for 70A.
Click to expand...

Thank you for the reassurance. 2x 10awg is equivalent to a single 7awg wire and no chart or forum posts I've seen says 7awg is fine for 100A (this forum tends to preach on oversizing on conductors).
 
Last edited:
If you look up awg tables, you're going to get the 60, 75 and 90°C ratings for enclosed wire in 30°C ambient.

Depending on the reference, 10awg wire won't fuse until > 300A for several seconds. The limit is the insulation and the conditions.

"battery" wire or "welding" wire has notably higher ampacity than what's in the awg chart.

newwiremarine.com

Marine Primary Wire

Marine primary wire, 16, 14, and 12 AWG. Sold in 25, 50, 100 and 250ft spools. Perfect for use on boats. Tinned, marine grade UL 1426 16 AWG Marine wire.
newwiremarine.com newwiremarine.com

1715315459306.png
 
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