is there a need for cells to be able to expand, or can they be compressed permanently?

[bordenov]

Will it damage the cells if they're in a fixture that doesn't allow them to expand, or is that kind of the point of compression?

I'm thinking of putting rubber on the ends of the battery (4 cell 280ah) if they do need to be able to have some wiggle room, but otherwise I can just enclose them in some thick cutting board and call it a day?

Also, my first battery failed because vibrations from having it in my van caused two of the cells to chafe against each other, so do you think rubber would be a better vibration proofing material between the cells over fr4 fiberglass sheets?

 

[Ampster]

Will it damage the cells if they're in a fixture that doesn't allow them to expand, or is that kind of the point of compression?

I believe that is the point of compression. Cylindrical cells can't expand either.. There are pressure relief valves in both types of cells.

 

[Substrate]

Also, my first battery failed because vibrations from having it in my van caused two of the cells to chafe against each other, so do you think rubber would be a better vibration proofing material between the cells over fr4 fiberglass sheets?

In your motive-power application, allowing cells to have wiggle room to move will put major strain on the rigid busbars, possibly damaging the terminals under vibration. Or at least cause intermittent loose connections. Nevermind the chafing.

You may want to look into braided interconnects, rather than rigid busbars. And nylock nuts, that are NEW and have NEVER been "backed out". And NO "starwashers" please.

 

[justgary]

It might be best to put your vibration damping outside your battery box. Use stiff insulation inside the box. Eve recommends "PC," which I take to mean polycarbonate. Docan provides FR4, which is the other type of "PC.". I suspect that either will work as long as you control the vibration from outside.

 

[Steve_S]

People get bent over "Binding vs Compression".
You want to "Bind" the cells together to make a solid block of cells to prevent movement/friction & terminal stress. The Compression issue that everyone trips on is whether should they compress to X PSI pressure... NO they do not ! It is the max limit for the binding, so as to not "squish" them too much but to be enough to make a solid block. In a static environment (residential non-mobile) this is less of an issue but in a mobile application, it is essential to bind them to prevent any movement.

FR4 is excellent as a separator between cells and has no give. Any metal casing the cells are installed in, should be lined by FR4 to prevent any contact with the casing. Several companies are now using 2mm EVA Foam between cells and then binding them tight, this prevents vibration, and friction and allows for a bit of "give".

EVA Foam is readily available everywhere, even art supply stores !
But here's amazon : https://www.amazon.com/eva-foam/s?k=eva+foam

 

[justgary]

The Compression issue that everyone trips on is whether should they compress to X PSI pressure... NO they do not !

They trip on it because the new Eve datasheets explain exactly how to do it and how much pressure to use.

 

[Lt.Dan]

This is just a dead horse now. Hundreds of threads EXACTLY like this one...

Moving on...

 

[OffGridForGood]

This is just a dead horse now. Hundreds of threads EXACTLY like this one...

Moving on...

LOL

youtube.com/watch?v=FdDy8b5x7Y8

 

[curiouscarbon]

They trip on it because the new Eve datasheets explain exactly how to do it and how much pressure to use.

EVE LF280K(-S04)

Source: Amy Wan Uploading from forum for ease of quick access

diysolarforum.com

this one?

 

[justgary]

EVE LF280K(-S04)

Source: Amy Wan Uploading from forum for ease of quick access

diysolarforum.com

this one?

For example, yes. They also have a similar one for LF230 cells.

The fixure is rigid, and the compression is set at 300kgf while the cells are at 30% to 40% SOC. No mention of expansion or constant compression force.

This is just a dead horse now. Hundreds of threads EXACTLY like this one...

Moving on...

I agree.

 

[Ampster]

And NO "starwashers" please.

I like to use Nordlok washers

 

[bordenov]

In your motive-power application, allowing cells to have wiggle room to move will put major strain on the rigid busbars, possibly damaging the terminals under vibration. Or at least cause intermittent loose connections. Nevermind the chafing.

You may want to look into braided interconnects, rather than rigid busbars. And nylock nuts, that are NEW and have NEVER been "backed out". And NO "starwashers" please.

I actually ordered some flexible busbars but it sounds like I should just have the cells bound together. Still gonna put those on once they arrive (from China so we'll see how long it takes to get here.) Thanks for your input!

 

[bordenov]

People get bent over "Binding vs Compression".
You want to "Bind" the cells together to make a solid block of cells to prevent movement/friction & terminal stress. The Compression issue that everyone trips on is whether should they compress to X PSI pressure... NO they do not ! It is the max limit for the binding, so as to not "squish" them too much but to be enough to make a solid block. In a static environment (residential non-mobile) this is less of an issue but in a mobile application, it is essential to bind them to prevent any movement.

FR4 is excellent as a separator between cells and has no give. Any metal casing the cells are installed in, should be lined by FR4 to prevent any contact with the casing. Several companies are now using 2mm EVA Foam between cells and then binding them tight, this prevents vibration, and friction and allows for a bit of "give".

EVA Foam is readily available everywhere, even art supply stores !
But here's amazon : https://www.amazon.com/eva-foam/s?k=eva+foam

thank you for this. I'll consider EVA over fr4 for what I put between the cells While we're at it do you have any recommended metal casings I can put the cells in? Should they definitely be put into a metal box? Some of the enclosures I've seen on here are pretty open and are mostly just two ends with all thread rods used to bind the cells together.

 

[bordenov]

It might be best to put your vibration damping outside your battery box. Use stiff insulation inside the box. Eve recommends "PC," which I take to mean polycarbonate. Docan provides FR4, which is the other type of "PC.". I suspect that either will work as long as you control the vibration from outside.

okay sounds good thank you. I'm considering sitting the box on top of a sheet of rubber for the vibration issue but someone else recommended EVA foam which seems to be a better fit.

 

[Steve_S]

thank you for this. I'll consider EVA over fr4 for what I put between the cells While we're at it do you have any recommended metal casings I can put the cells in? Should they definitely be put into a metal box? Some of the enclosures I've seen on here are pretty open and are mostly just two ends with all thread rods used to bind the cells together.

I can't suggest anything for metal enclosures as such, I make my own boxes to "made to measure" with 3/4" Plywood using pocket screws & the like as I used to make cabinetry. Hell, I designed & built my home so.... got the tools, materials & know how...

Generic metal enclosures are available for all sorts of things, the trick is to find something you like that fits the cells. Now Luyuan Tech has Battery Cases, similar to what Seplos but more generic but is it worth ordering those, paying duties etc and waiting for the boat from China ? Unless you ordered the cells & BMS etc from them too. Now anyone with a decent Break Press can fold up metal and make a box to "spec", again quite simple if you know how to draw out the design and get someone to do it and then you rivet, screw or weld it together. Search for "Sheet Metal Fabrication" in your area, you might be surprised. IE one of the best near me: https://www.bayviewmetals.com/precision-custom-sheet-metal-fabrication/ Pretty much every major city has someone that does that kind of work... If you have a buddy who works in a good Autobody shop they could likely whip up a box or two as well.

 

[Ellcon123]

Maybe we can get this thread to 30+ pages? Forum search should be the answer.

 

[curiouscarbon]

Maybe we can get this thread to 30+ pages? Forum search should be the answer.

lets make a wiki page! ?

then people can paste a link to the Cell Compression Wiki page and be sure the basics get across

 

[bass-o-matic]

People get bent over "Binding vs Compression".
You want to "Bind" the cells together to make a solid block of cells to prevent movement/friction & terminal stress. The Compression issue that everyone trips on is whether should they compress to X PSI pressure... NO they do not ! It is the max limit for the binding, so as to not "squish" them too much but to be enough to make a solid block. In a static environment (residential non-mobile) this is less of an issue but in a mobile application, it is essential to bind them to prevent any movement.

FR4 is excellent as a separator between cells and has no give. Any metal casing the cells are installed in, should be lined by FR4 to prevent any contact with the casing. Several companies are now using 2mm EVA Foam between cells and then binding them tight, this prevents vibration, and friction and allows for a bit of "give".

EVA Foam is readily available everywhere, even art supply stores !
But here's amazon : https://www.amazon.com/eva-foam/s?k=eva+foam

Thanks! I'm doing my first build and this is exactly what I was looking for. Seems to be a LOT of contradictory and unclear as hell info on the "interwebs" of confusion.