Bms lug on battery pole or not?

[Pink7]

Just did some very simple testing on my LiFePo4 battery with BMS lug on the battery pole and i got a feeling that i get better tightening without the BMS lug? So whats your experiences and opinions: BMS lug on battery pole or use its own hole and bolt?

 

Pink

[Crossy]

Correctly sized (for cable and battery stud) ring-crimp/lug on the BMS cable.

 

Everything thoroughly cleaned (sanded).

 

Decent electrical jointing compound on the mating faces if that's your thing, some don't like it.

 

Washer ONLY on the top, never between the crimp and battery.

 

EDIT Not exactly what you have, but you get the idea.

 

[Pink7]

3 hours ago, Crossy said:

Correctly sized (for cable and battery stud) ring-crimp/lug on the BMS cable.

 

Everything thoroughly cleaned (sanded).

 

Decent electrical jointing compound on the mating faces if that's your thing, some don't like it.

 

Washer ONLY on the top, never between the crimp and battery.

 

EDIT Not exactly what you have, but you get the idea.

 

Good idea with spring washer.. On all batteries or only main + and main -?

 

Pink

[Pink7]

I may miswrite my initial post a bit? I tried to discuss placement of the lugs for BMS wires going to each positive pole. I see some prefer to place them on the bars connecting the batteries not on the pole itself.

 

Pink

[Crossy]

OK, I get what you are talking about now.

 

I'm not sure it makes much difference to performance, but the presence of a smaller lug on top of the main battery connection may reduce the effectiveness. Commercial packs vary, but many use laser-welded cell connections meaning they have to connect to the cell interconnect.

 

Of the three packs I've built all have the BMS sense leads on the interconnect bars. The first I actually soldered the wires on (you need a BIG soldering iron) the other two are drilled and tapped M4 with crimped lugs on the sense wires.

[lom]

7 hours ago, Crossy said:

the other two are drilled and tapped M4 with crimped lugs on the sense wires.

That's the right way to do it.

[sometimewoodworker]

21 hours ago, Pink7 said:

Good idea with spring washer.. On all batteries or only main + and main -?

 

Pink

There is considerable debate on the benefits, or total lack or benefit, regarding a spring washer.

 

The force possible exerted by a spring washer is much less than the clamping force of the fastener, so it’s a placebo or only used if you can’t actually tighten the fastener correctly. Then there is the geometry of a spring fastener which when compressed is just a narrow washer.