JK BMS 200A - One terminal enough for how much current?

[meetyg]

I have the 200A JKBMS for 8S Lifepo.
When connecting to the cells, I was wondering how much current one terminal (on each side) could handle?

My dilemma is if I should use both terminals on each side with 6 AWG wire each, or if I can get away with using just one terminal with a 4 AWG ?

I know that double 6 AWG should handle more current, but it makes the cabling more cumbersome (either use two lugs on the cell, or one large lug with two wires).
The single 4 AWG would be alot more elegant and simple.

How much current would you rate each option at (using 200C rated silicone insulated wire) ?

While I don't plan to push it, I would like to be able to pull around 100A from the cells (105Ah cells) if needed.

I mentioned these wire sizes as this is what I have at hand.

Thanks.

 

[Ahjwinth]

I have the same BMS B2A8S2oP on 8S 280AH battery in my mobile home. I just assembled everything 2 weeks ago and during the commissioning I tested everythinog to the max. I have a 2000VA inverted and pulled continuously until the battery was depleted 80a. The inverter was connected to massa with a single 25mm2 wire on a single terminal of the BMS. The battery side is also connected on a single terminal with a 25mm2 wire. I checked with a FLIR One pro thermal camera and the temperature of the terminals were not higher than the temperature of the BMS. Since the BMS also gets warm it is difficult to detect if the heat is coming from the terminals or the mosfets. So if the terminals have the same temperature then the mosfets this to me indicates it is not an issue.

See the picture of the battery and BMS on the side.

 

[fdom]

I used a 50mm2 cable and split the leads to 2 x 25mm2 at one end, crimped 2 25mm2 lugs and isolated the exposed copper again. So i have one 50mm2 lug at one end and 2 25mm2 lugs at the other. Works like charm. You just need to make sure tonprecisely split 50-50.

It is probably oversized but I usually go rather conservative.

 

[meetyg]

I used a 50mm2 cable and split the leads to 2 x 25mm2 at one end, crimped 2 25mm2 lugs and isolated the exposed copper again. So i have one 50mm2 lug at one end and 2 25mm2 lugs at the other. Works like charm. You just need to make sure tonprecisely split 50-50.

It is probably oversized but I usually go rather conservative.

I might try that, thanks.

 

[740GLE]

I used a 50mm2 cable and split the leads to 2 x 25mm2 at one end, crimped 2 25mm2 lugs and isolated the exposed copper again. So i have one 50mm2 lug at one end and 2 25mm2 lugs at the other. Works like charm. You just need to make sure tonprecisely split 50-50.

It is probably oversized but I usually go rather conservative.

How bad was it to crimp that dual lug?

Did you have to do anything special to get both leads into the lug before crimping?

 

[RCinFLA]

Avoid too much flexing stress on BMS printed circuit board due to heavy gauge wire.

Current shunt chip resistors are near wire terminal connections and the MOSFET's two rows wire jumpers' solder joints between MOSFET's are subject to fracturing.

 

[meetyg]

Yeah, working with thick wire is cumbersome too (my cells are in a battery box, so wire will need to be flexed). Thats why I think 4AWG is the maximum I would use... 2 AWG (or 50mm²) is a bit too much.

 

[rhino]

You can get some pretty flexible cabling even at thicker gauges. For welding cable you usually see Class K but if you look for Class M it has twice as many strands using smaller gauge strands..

 

[fdom]

How bad was it to crimp that dual lug?

Did you have to do anything special to get both leads into the lug before crimping?

I took a 50 mm2 cable removed the isolation at one end for about 7cm (2.5 inch) and seperated the leads into 2 bunches. The I fitted 1 25mm2 lug to each of the lead bundles. Please dry fit both at the same time before crimping one to make sure you got it approx 50-50. Afterward insulate the exposed wires with shrink pipe.

I tried before to fit 2 25mm2 cables into one 50mm2 lug but the result was not satisfying for me.

I used fine stranded wire which was super flexible but getting the strands into lug required a whole lot of patience ;-)

 

[rhino]

Steve_S did this: https://diysolarforum.com/threads/jk-bms-two-cables-in-one-lug.40496/post-512042