JK BMS 200A (350A peak). 2x 7AWG. HOW?

[solarrig]

JK BMS, rated at 200A current with 350A peaks. Have two 7AWG cables on B- and two 7AWG cables on P-. How this is possible? Does anyone had a problems with it?
7AWG cable rated to 30-40A. Two of those will double accordingly 60-80A. Is it safe to use?

 

[timselectric]

JK BMS, rated at 200A current with 350A peaks. Have two 7AWG cables on B- and two 7AWG cables on P-. How this is possible? Does anyone had a problems with it?
7AWG cable rated to 30-40A. Two of those will double accordingly 60-80A. Is it safe to use?

They are silicone jacketed, super fine strand. And very short.
Not a problem.

 

[Dzl]

JK BMS, rated at 200A current with 350A peaks.

Can you link to the specific BMS you are referencing

How this is possible?

7AWG cable rated to 30-40A. Two of those will double accordingly 60-80A.

I'm not sure where you are getting these numbers from but I don't think they are accurate.

Ampacity of the wire depends on a number of factors, including the insulation temperature rating and ambient air temperature. My guess is that the 30-40A number you quoted is very conservative.

You can see on this Marine Ampacity table, 7AWG wire with an insulation temperature rating of 105*C and an ambient of <=30*C (86*F) has current carrying capacity of ~70A. This type of BMS often uses silicone wire with an even higher temp rating (often 125-200*C)

Is it safe to use?

Personally I'd derate by at least 20% (not just because of the wire specifically, just because I think its the prudent thing to do with components like this).

 

[DIYrich]

JK BMS, rated at 200A current with 350A peaks. Have two 7AWG cables on B- and two 7AWG cables on P-. How this is possible? Does anyone had a problems with it?
7AWG cable rated to 30-40A. Two of those will double accordingly 60-80A. Is it safe to use?

Depends on how long, and chassis wiring:

Battery Cable Amperage Capacity Chart

Recommended Length and Amperage for Battery Cable while maintaining a 2% or less voltage drop at 12 volts Battery Cable Size 50 Amps 100 Amps 150 Amps 200 Amps 300 Amps 6 Gauge (AWG) 11.8 ft 5.9 ft 4.4 ft 2.9 ft 2.2 ft 4 Gauge (AWG) 18.8 ft 9.4 ft 6.3 ft 4.7 ft 3.1 ft 2 Gauge (AWG) 29.8 ft...

wiringproducts.com

You are thinking wire in conduit for any length.

 

[solarrig]

They are silicone jacketed, super fine strand. And very short.
Not a problem.

Yeah... i'm somehow did not think about length. That's right. They are very short. Maybe super fine strand also makes sense. But silicone jacket? It does not acting in power transmission Why you mentioning it? Higher temp. resistance?

 

[solarrig]

Depends on how long, and chassis wiring:

Battery Cable Amperage Capacity Chart

Recommended Length and Amperage for Battery Cable while maintaining a 2% or less voltage drop at 12 volts Battery Cable Size 50 Amps 100 Amps 150 Amps 200 Amps 300 Amps 6 Gauge (AWG) 11.8 ft 5.9 ft 4.4 ft 2.9 ft 2.2 ft 4 Gauge (AWG) 18.8 ft 9.4 ft 6.3 ft 4.7 ft 3.1 ft 2 Gauge (AWG) 29.8 ft...

wiringproducts.com

You are thinking wire in conduit for any length.

yeah. my fault. Cable length.... did not counted it.

 

[tim0shel]

I'm running dual 6 awg silicone fine strand cable no issues but not many times I'll be pulling max current. Plus the runs are not crazy long.
https://www.timshelnut.com/Electronics/Portable-Power-Station-Banana-Dos/

 

[timselectric]

Higher temp. resistance?

Exactly
Which also gives the conductor a higher amperage rating.