BMS bus too small for 6 gauge lugs - how to work around

[big_shootr]

I purchased a 160A LiFePO4 BMS off the good ole AliExpress to go in my waterproof Pelican case with 4x120Ah LiFePO4 cells. I want a direct 6 gauge connection to a 50A connector on the outside of the box. Unfortunately the bus bar on the negative side has some components on the PCB that are dangerously close to where the lug would end up, they are the same on both top and bottom of the bus so I can't just flip it over. This high amp output will function as both a car battery jump starter and running a trolling motor on my boat, so I do need the 6 gauge and don't want to compromise going smaller. How should I go about this? Run a pair of smaller 10 gauge cables to a larger bus bar and connect to that? Grind down the tip of the lug? Thanks in advance.

 

[Messier11]

I purchased a 160A LiFePO4 BMS off the good ole AliExpress to go in my waterproof Pelican case with 4x120Ah LiFePO4 cells. I want a direct 6 gauge connection to a 50A connector on the outside of the box. Unfortunately the bus bar on the negative side has some components on the PCB that are dangerously close to where the lug would end up, they are the same on both top and bottom of the bus so I can't just flip it over. This high amp output will function as both a car battery jump starter and running a trolling motor on my boat, so I do need the 6 gauge and don't want to compromise going smaller. How should I go about this? Run a pair of smaller 10 gauge cables to a larger bus bar and connect to that? Grind down the tip of the lug? Thanks in advance.

View attachment 104342

I would take a piece of a copper buss bar and cut two smaller pieces of it and mount it like this with M6 bolts on the BMS and then the M8 bolt (or M8/10, can’t really tell the sizes from the picture) on the cable lug (the red painted parts are the copper bus bar and the blue is the cable lug):

 

[big_shootr]

Thank you, I quite like that idea.

I would take a piece of a copper buss bar and cut two smaller pieces of it and mount it like this with M6 bolts on the BMS and then the M8 bolt (or M8/10, can’t really tell the sizes from the picture) on the cable lug (the red painted parts are the copper bus bar and the blue is the cable lug):
View attachment 104352

I may simplify it a bit and just cut a single square piece of some flat bar and drill holes to line up with the BMS. Wouldn't have thought of that without you, thanks again!

 

[HRTKD]

Thank you, I quite like that idea.

I may simplify it a bit and just cut a single square piece of some flat bar and drill holes to line up with the BMS. Wouldn't have thought of that without you, thanks again!

I think that's a good suggestion. A square of copper may be harder to come by than a bar. Or, it would be a really wide bar.

Another option is to grind off the nose of the lug so it doesn't make contact. It does look like you're using a 3/8" lug when a 5/16" or 1/4" would do.

 

[740GLE]

What size are the holes in the BMS? They aren’t threaded correct?

AFAIK you’re supposed to solder you’re leads directly to those copper terminals.