Threads vs Posts on Alibaba LifePo4 cells

[Barbar0ssa]

I am noticing on Alibaba that similar cells are offered with either threads or 1 cm posts. Threads allow you to bring your own screws for any length but I've heard that people are stripping them out. Are posts more resilient? Is 1 cm long enough? Am I overthinking this and it really doesn't matter?

 

[blutow]

The threads are a much debated issue. The aluminum is soft and the holes are very shallow, so they are prone to being stripped. There has also been reports of the holes being tapped crooked and just generally poorly machined threads.

I'm pretty new to this stuff, but it seems like the welded on studs have not been a common option on the popular commodity cells. It seems that some suppliers are offering them now, but I think it's been pretty recent and I have not seen any reports on how the studs are working out yet.

I got my cells (with threads) last week and I used red loctite to permanently install the studs (grub screws) provided. They seem really solid, but time will tell how they hold up. I am installing them in a van (high vibration), so it will be a good test. If I have issues, my plan is to install helicoils in all cells.

If I was buying cells today and had the option to do threads or welded on studs, I'd probably go studs. I'd rather the studs be longer than 1cm, but I could make 1 cm work. The current unknows on studs from my perspective:

• How securely are the studs welded on to the terminals? If they pop off when high torque is applied, that's probably worse than a stripped thread (there is really no good way to weld it back on without specialty welding equipment). I think this is pretty low risk, but you never know with some of these vendors.
• Does the smaller mating surface on the stud create any challenges with the electrical connection to the bus bars?

 

[HRTKD]

If the surface area really is as small as presented in the picture in post #1, I'll take threads. So far, my threaded terminals are doing OK.

 

[Bob B]

I had the same thought as HRTKD. There appears to be 3 steps on those posts and very little surface area for the buss bar to contact the pad.

 

[blutow]

Yeah, it will be interesting to see if there are resistance issues with the welded studs. If I had to make a bet, I'd say they are going to work well. It's not all about size (so they say). A quality connection with a small surface beats a marginal connection over a large surface every time. With M8 studs and no concerns about proper torque, I think it will be enough surface area to produce a solid connection.

If I was doing a stationary install, I wouldn't have any concerns about my threads, they seem really solid with the loctite. My concern is with my mobile install where there will be a lot of vibration. I believe studs would be the more reliable approach there. We'll see how they perform once people start getting them in hand. I believe Michael Caro placed a big order of lishens with studs a while back (right after I ordered mine) to help support the group buy activity, so I'd expect some of those to start showing up soon.

 

[Bob B]

Yeah, it will be interesting to see if there are resistance issues with the welded studs. If I had to make a bet, I'd say they are going to work well. It's not all about size (so they say). A quality connection with a small surface beats a marginal connection over a large surface every time. With M8 studs and no concerns about proper torque, I think it will be enough surface area to produce a solid connection.

If I was doing a stationary install, I wouldn't have any concerns about my threads, they seem really solid with the loctite. My concern is with my mobile install where there will be a lot of vibration. I believe studs would be the more reliable approach there. We'll see how they perform once people start getting them in hand. I believe Michael Caro placed a big order of lishens with studs a while back (right after I ordered mine) to help support the group buy activity, so I'd expect some of those to start showing up soon.

I agree with what you are saying .... in theory .... but did you actually look at the pictures of those cells? There is not way to put a buss bar on there properly.

I have seen other laser welded terminals that didn't look like those.

 

[HRTKD]

If the bolt hole on the bottom of the bus bar was countersunk to fit snugly over the step of the base of the stud that might improve the contact area. But that's a lot of assuming.