Will my custom battery build work? (photo)

[ggos]

Hello, new here, wondering if anyone has any thoughts on my attempt at a battery build for my ebike I built from scratch.

I 3d printed a case for the 38 cells (gotion 3.2v lifepo4). I am doing 2 in parallel and 19 in series. I 3d printed thin sides for it, and I was going to just glue copper on in the wiring pattern, hook up my JK BMS, and give it a go, but I was advised by someone with a lot of battery building experience to not do that!! He suggested I use Pouron foam on the inside, and that I needed some way to make the sides more stiff, so maybe carbon or I was just thinking glue on another thick 3d print layer that would make it thick and sturdy enough.

I am open to any and all ideas, as I really want to get this battery build the simplest and cheapest way possible... Thanks so much.

 

[Comrade]

I was going to just glue copper on in the wiring pattern

And bolt on the side along the perimeter with 4 bolts and expect all electrical points to make good contact?

 

[ggos]

Exactly. With a magnet in the center to make sure it was touching all the cells enough

 

[MxusMick]

Tough bike, I wouldn't want a short to the frame, your skills are much better than mine

 

[Hummina Shadeeba]

I think you should search what thickness Poron foam to use and what density it needs to be. Agnasium here on the forum did a lot of testing and sold compression battery holders he designed.


The only needs are have the right foam and right amount of compression, have the plates behind the foam rigid enough, and keep the copper sheet safely in place

 

[Comrade]

Exactly. With a magnet in the center to make sure it was touching all the cells enough

That won't work. At all. If you are determined to use compression to make contact that side panel needs way more bolts strategically placed all over. And the bolts need to be spring loaded, so they are always pushing down. The cover doesn't need to be stiff, but the opposite.

 

[Zambam]

Exactly. With a magnet in the center to make sure it was touching all the cells enough

Did you try a magnet on the cells? It will not stick to the copper tabs!

 

[Hummina Shadeeba]

The cover doesn't need to be stiff, but the opposite.

I’m meaning the cover needs to be stiff so can use fewer bolts to compress it against the cells so it won’t bow.

 

[Hummina Shadeeba]

Did you try a magnet on the cells? It will not stick to the copper tabs!

He’s got another magnet on the cell side to pull to.

 

[Zambam]

He’s got another magnet on the cell side to pull to.

Interesting! He didn't mention that anywhere or showed it in his photos. How are the magnets attached to the cells? Neodymium magnets are plated with nickel and needs to be insulated against shorts to the aluminum cell casing on these Gotian cells (which is floating with respect to the + / - copper tabs).

I built a 22S2P pack with these Gotian cells by soldering 0.3 mm copper sheets. Have probably 1000 miles on battery so far, doing well.

 

[Comrade]

I’m meaning the cover needs to be stiff so can use fewer bolts to compress it against the cells so it won’t bow.

More bolts. Less bolts. It's still a very bad design. About as bad as it can get. The only thing that can save it is spring loaded electrical contacts.

 

[Hummina Shadeeba]

More bolts. Less bolts. It's still a very bad design. About as bad as it can get. The only thing that can save it is spring loaded electrical contacts.

Why not poron foam? That’s how it’s typically done. This design is a pretty standard compression battery design that just needs more bolts, foam, and a stiffer plate as far as I can tell. What you not like specifically?


The cells are held pretty firmly by the honeycomb as well. They’re pretty tightly in there though.

 

[Hummina Shadeeba]

How are the magnets attached to the cells?

Magnet pulling to a single magnet in the center of the battery. I think he’s better off with a very stiff plate instead to stop the bowing


Maybe soldering would be easier. Maybe not.

 

[Hummina Shadeeba]

built a 22S2P pack with these Gotian cells by soldering 0.3 mm copper sheets.

How did u do that? I’m imagining blindly having to weld four cells to the copper sheet from the outside. Or I guess you could assemble the cells together cell by cell while soldering

 

[Zambam]

How did u do that? I’m imagining blindly having to weld four cells to the copper sheet from the outside. Or I guess you could assemble the cells together cell by cell while soldering

Tin everything first. All 44 cells in clamshell holders. Use a big iron. I got inspiration from this video (not mine).

 

[Zambam]

Magnet pulling to a single magnet in the center of the battery. I think he’s better off with a very stiff plate instead to stop the bowing

I thought he was going to use a magnet on each cell. One magnet in the center of the pack won't provide much force to make good contacts on all cells.

 

[Zambam]

needed some way to make the sides more stiff, so maybe carbon

Carbon fiber is conductive so forget it.

 

[Hummina Shadeeba]

Carbon fiber is conductive so forget it.

Carbon maybe even just on the outside of the plate, or even the inside as then there’s like 1/2” of foam, then the conductors.