Compress or not, flexible busbar or not

[Cheap 4-life]

Shouldn't you have some sort of insulator between the end plates and each cell?

The cells come with separators that go between each cell. At the ends I used 1/8” hard rubber sheet shown in post #808. They have the nuts and washers for the threaded rod sitting on top

 

[Skypower]

The cells come with separators that go between each cell. At the ends I used 1/8” hard rubber sheet shown in post #808. They have the nuts and washers for the threaded rod sitting on top

Could you do me a favor and check and re torque the flexible buss terminals? I’m super curious if the buss’s crush or yield. A tiny bit would be expected(just detectable) but some movement might be a concern. Even more if a week later there’s more movement.

 

[Cheap 4-life]

Could you do me a favor and check and re torque the flexible buss terminals? I’m super curious if the buss’s crush or yield. A tiny bit would be expected(just detectable) but some movement might be a concern. Even more if a week later there’s more movement.

I will, but when I got the serrated nuts torqued to 85inlbs the busbars just turned on the terminals surface. I held the busbars in place to make sure I was giving the nuts 85 but if I wanted to I could still by hand turn the busbars and the busbar would then flex in the middle.
I’m using laminated flexible busbars not braided. The laminated are so hard that they can be tapped for threads as I described I did for the balance wires. There will not be any noticeable crushing that causes torque issues

 

[justgary]

I held the busbars in place to make sure I was giving the nuts 85

Wow, I'm not all that comfortable with 70 in-lbs (~8 N-M) since I don't really know what grade of steel I have in the 6mm studs.

 

[Skypower]

I will, but when I got the serrated nuts torqued to 85inlbs the busbars just turned on the terminals surface. I held the busbars in place to make sure I was giving the nuts 85 but if I wanted to I could still by hand turn the busbars and the busbar would then flex in the middle.
I’m using laminated flexible busbars not braided. The laminated are so hard that they can be tapped for threads as I described I did for the balance wires. There will not be any noticeable crushing that causes torque issues

Yes, I realize you have the laminated type. I don’t have those and was very curious. You may want to go check the the torque specs from your cell manufacturer. That indeed seems high. I’ve got mine at 4Nm or (36 inlbs). There’s one confusingly worded document out there for one brand that listed the torque where the terminal was likely to rotate in the case. In other words “don’t go there” but got lost in translation.

 

[Cheap 4-life]

My cells have the welded studs. I couldn’t see how the terminal could rotate in the case. At 85inlbs the serrated nut is thoroughly grabbing onto the busbar but the busbar still spins on the terminal bed by hand if I tried hard enough to spin it. The busbar flexes in the middle when I do this. Makes me think it’s certainly not to tight..
I rechecked my torque and still 85inlbs.. don’t know what the torque spec should be because the cell spec sheet I was emailed was for the cells without the welded studs. And for those I think it was 35inlbs so they don’t strip out

 

[SolaroSsaurius]

About the rods used in these battery "cases", should they be stainless steel or zinc plated steel is perfectly OK?
Asking as there is a huge price difference (6x) between them...
(In any case, they will be enclosed in rubber tubing)

Thanks in advance for all opinions!

 

[justgary]

don’t know what the torque spec should be

Nothing really changes by the use of the fastener; the torque is specified by the type of material and the size. Lots of charts online, but again, we really don't know the material they used. I thought they were stainless, but now they look zinc plated after close inspection. Either way, I'll be a bit conservative since I don't care to twist one off.

 

[justgary]

About the rods used in these battery "cases", should they be stainless steel or zinc plated steel is perfectly OK?
Asking as there is a huge price difference (6x) between them...
(In any case, they will be enclosed in rubber tubing)

Thanks in advance for all opinions!

Zinc plated should be just fine, and much easier on your pocketbook.

 

[SolaroSsaurius]

Zinc plated should be just fine, and much easier on your pocketbook.

Thanks for your input!!

 

[Cheap 4-life]

Nothing really changes by the use of the fastener;

Are you saying there’s no difference between welded studs and threads? I have read 35inlbs for threads and 85inlbs for studs. Searched on here for torque for welded studs and 85inlbs was the result. That wasn’t my max, it was the torque recommended

 

[justgary]

Are you saying there’s no difference between welded studs and threads? I have read 35inlbs for threads and 85inlbs for studs. Searched on here for torque for welded studs and 85inlbs was the result. That wasn’t my max, it was the torque recommended

I'm saying that if you have a 6mm fastener, it is a 6mm fastener. Since your fasteners are welded, you aren't concerned with torque for aluminum. Steel and stainless have different strengths, so it matters which you have.

 

[filippomasoni]

That is basically what I did, my cells are set at 640psi and mounted on vibration dampers. I go off road quite a bit for work and they have been holding up for about a year and a half. If you are heating you have air space under the cells for air circulation as well.

Hi @S Davis. I have a further question: Do you have anything supporting the cells on the bottom of the compression rig? Or are they directly resting on what looks like an aluminum plate in the photo?

I really like your setup, and I'm trying to design something similar in my build. As that's a very heavy load for my camper I was thinking of placing it closer to the cab and having the two water tanks on each side, this way I have the best weight balance. But I want the cells to be suspended a bit from the floor so that in case of any leaks or flooding in the camper they don't short out. Hopefully, it will never happen, but better safe than sorry. You also have the enclosure on the outside that can be sealed, but I feel like that adds unnecessary weight and I'm looking for something alternative.

 

[justgary]

Hi @S Davis. I have a further question: Do you have anything supporting the cells on the bottom of the compression rig? Or are they directly resting on what looks like an aluminum plate in the photo?

I really like your setup, and I'm trying to design something similar in my build. As that's a very heavy load for my camper I was thinking of placing it closer to the cab and having the two water tanks on each side, this way I have the best weight balance. But I want the cells to be suspended a bit from the floor so that in case of any leaks or flooding in the camper they don't short out. Hopefully, it will never happen, but better safe than sorry. You also have the enclosure on the outside that can be sealed, but I feel like that adds unnecessary weight and I'm looking for something alternative.

I have no idea about the availability of these isolators, but I have seen them on various pieces of equipment and they seem to work quite well. The good news is that you can make them yourself if you are willing to do a bit of experimenting with cable size and loop diameter/count.

https://www.isolator.com/isolators/sm-series/

 

[S Davis]

Hi @S Davis. I have a further question: Do you have anything supporting the cells on the bottom of the compression rig? Or are they directly resting on what looks like an aluminum plate in the photo?

I really like your setup, and I'm trying to design something similar in my build. As that's a very heavy load for my camper I was thinking of placing it closer to the cab and having the two water tanks on each side, this way I have the best weight balance. But I want the cells to be suspended a bit from the floor so that in case of any leaks or flooding in the camper they don't short out. Hopefully, it will never happen, but better safe than sorry. You also have the enclosure on the outside that can be sealed, but I feel like that adds unnecessary weight and I'm looking for something alternative.

The cells sit on two pieces of 3/8” all thread with 1/2” pex pipe covering them.

 

[filippomasoni]

The cells sit on two pieces of 3/8” all thread with 1/2” pex pipe covering them.

Oh, interesting, so one of the bottom rods is not on the side but actually below. Really clever and makes perfect sense now. Thanks!

 

[justgary]

Oh, interesting, so one of the bottom rods is not on the side but actually below. Really clever and makes perfect sense now. Thanks!

I thought you were asking about his shock isolators. One of his photos showed them. They should be important in a mobile application to keep high frequency vibration from disturbing the batteries.

 

[filippomasoni]

I thought you were asking about his shock isolators. One of his photos showed them. They should be important in a mobile application to keep high frequency vibration from disturbing the batteries.

Those are important as well, and I'm going to use it, but I wanted to know how the cells are supported on the bottom and the single rod is great idea

 

[SolaroSsaurius]

That also tend to be very low impedance devices, which require special amplifiers to use. I'm not saying you couldn't use them. I have a small pile of them that I got surplus. I'll check them to see if I could get them to work.

Hi!

Were you able to make it work?
I haven't bought them (yet) given your thoughts, but the diagram to make it works seems quite easy with an Arduino (I'll try to dig it).
My idea is to have a log / graph crossing temperature, SOC and pressure in a spring loaded "case".
That would be used as an alarm if readings jump out of the ordinary

 

[SolaroSsaurius]

The cells sit on two pieces of 3/8” all thread with 1/2” pex pipe covering them.

Hi!

Is this for stationery application or mobile?
Because if mobile, given the cell's weight, I believe rubbing due to vibration could lead to PEX's failure