Wire gauge for JBD 150a bms

[Just John]

I got a JBD 150A BMS from Current Connected here. I wanted the 150A BMS so I could potentially pull up to 150 A to power a 1500 watt inverter (at 12v)…( at least I think 150A should be adequate for that.)

I also purchased “Y” cables from Current Connected (sold as an accessory) to hook up the BMS to my batteries and to my load. The Y cables are 6 AWG.

However, I’m confused as to whether the two 6 AWG cables are big enough to safely carry 150A? This Blue Sea chart makes it look like 3 AWG (or 2 x 6 AWG) would be safe for 180A (so fine for 150A). But this thread makes it seem like 2x6AWG are just barely adequate, so I should increase the wire size to 2x4AWG. And this other Blue Sea chart seems to recommend at least 1 AWG for 150A?

Basically if I want to use this BMS to safely provide power up to the capacity of the BMS do I need to use 2x4AWG cables in parallel instead of the 2x6 AWG cables?

Also, do I understand correctly that to find the correct fuse size to protect the wires, I need to divide the max amp rating for the wire by 0.8? I thought you wanted your fuse to give up well before your wires… so you would want a fuse rated LESS than the rating of the wires. I was planning on using a dc circuit breaker (blue sea), but only seem to be able to find 150A or 200A, so it seems my options are limited there. I’m not opposed to using a fuse if that’s a better idea.

Thanks for any input or advice you can provide to this newbie!

Two 6 gauge wires should handle the 150 amps max current just fine, or it does for the 4 I have.
200 amp is what you should rate the fuse (or circuit breaker) for. The wire would get hot, but not fail at that rate, and the fuse is to protect the wiring. Your BMS should also shut off when it goes above 150 amps for an extended time.

If you wish to use two 4 gauge wires, nobody will stop you!

I used this wire:

https://smile.amazon.com/gp/product/B01MDPWSKV/

To purchase similar wire (flexibility wise) I would have to order from China. That's why I used 6 gauge rather than 4 gauge.

 

[EcoRV]

I got a JBD 150A BMS from Current Connected here. I wanted the 150A BMS so I could potentially pull up to 150 A to power a 1500 watt inverter (at 12v)…( at least I think 150A should be adequate for that.)

I also purchased “Y” cables from Current Connected (sold as an accessory) to hook up the BMS to my batteries and to my load. The Y cables are 6 AWG.

However, I’m confused as to whether the two 6 AWG cables are big enough to safely carry 150A? This Blue Sea chart makes it look like 3 AWG (or 2 x 6 AWG) would be safe for 180A (so fine for 150A). But this thread makes it seem like 2x6AWG are just barely adequate, so I should increase the wire size to 2x4AWG. And this other Blue Sea chart seems to recommend at least 1 AWG for 150A?

Basically if I want to use this BMS to safely provide power up to the capacity of the BMS do I need to use 2x4AWG cables in parallel instead of the 2x6 AWG cables?

Also, do I understand correctly that to find the correct fuse size to protect the wires, I need to divide the max amp rating for the wire by 0.8? I thought you wanted your fuse to give up well before your wires… so you would want a fuse rated LESS than the rating of the wires. I was planning on using a dc circuit breaker (blue sea), but only seem to be able to find 150A or 200A, so it seems my options are limited there. I’m not opposed to using a fuse if that’s a better idea.

Thanks for any input or advice you can provide to this newbie!

As i mentioned i used dual 4ga. As you have purchased the "Y" cables why not give them a try at 150amps and report back to us. Also it would be helpful to describe you build - like if its in a tight closed environment of more of a free air environment.

 

[Rustynuts]

I went with 4ga myself.

 

[squowse]

I got a JBD 150A BMS from Current Connected here. I wanted the 150A BMS so I could potentially pull up to 150 A to power a 1500 watt inverter (at 12v)…( at least I think 150A should be adequate for that.)

I also purchased “Y” cables from Current Connected (sold as an accessory) to hook up the BMS to my batteries and to my load. The Y cables are 6 AWG.

However, I’m confused as to whether the two 6 AWG cables are big enough to safely carry 150A? This Blue Sea chart makes it look like 3 AWG (or 2 x 6 AWG) would be safe for 180A (so fine for 150A). But this thread makes it seem like 2x6AWG are just barely adequate, so I should increase the wire size to 2x4AWG. And this other Blue Sea chart seems to recommend at least 1 AWG for 150A?

Basically if I want to use this BMS to safely provide power up to the capacity of the BMS do I need to use 2x4AWG cables in parallel instead of the 2x6 AWG cables?

Also, do I understand correctly that to find the correct fuse size to protect the wires, I need to divide the max amp rating for the wire by 0.8? I thought you wanted your fuse to give up well before your wires… so you would want a fuse rated LESS than the rating of the wires. I was planning on using a dc circuit breaker (blue sea), but only seem to be able to find 150A or 200A, so it seems my options are limited there. I’m not opposed to using a fuse if that’s a better idea.

Thanks for any input or advice you can provide to this newbie!

Two smaller cables can dissipate more heat than one big one. So the theoretical maximum current rating will be higher.

 

[shadowsteve]

Two smaller cables can dissipate more heat than one big one. So the theoretical maximum current rating will be higher.

I would think if you are taking heat dissipation into account then you are definitely undersized on the cable. I'm running double 4's

 

[squowse]

I would think if you are taking heat dissipation into account then you are definitely undersized on the cable. I'm running double 4's

Heat dissipation is what determines ampacity of cable. That and the resistance per metre.

 

[Just John]

For me, trying to pull more than 140 amps out of a 280 amp hour cells is not my intent. I intend to keep any sustained draw below 100 amps. A 6 gauge wire by itself is rated for 70 amps, without high temperature insulation. Two 6 gauge wires works for me, your mileage may vary.