jonescg's battery builds (historical reference - image heavy)

[electric_nz]

These are amazing! Such neat and tidy work too. Love the old school prelude

 

[CONSIDERABLE SHOUTING]

Interesting to see how you're getting the pouch cells to work- I'm honestly scared deathless of them, which is funny to say when cylindrical cells aren't much different!
Any other tips you could share about building with them?

 

[nicobie]

I knew you have been making batteries for ES members for years. I didn't know how advanced and good at it you were getting. Very, very clean.

 

[jonescg]

Treat a pouch cell like an unpeeled banana. Very fragile, and needs to be well supported in a robust, movement-free compressive arrangement. Physical trauma is a really common source of fail, along with water ingress which causes the foils to corrode and the cells to eventually short and drain. Be careful of the tabs, and make sure there's little chance of the tab fretting against another cell, or something which can cause a short. Also, try not to put the tabs under any kind of tension - they rip out easy enough.

I never put much effort into ensuring consistent pressure was applied - something that would make the battery live a very long life, because these aren't expected to be in service for more than 3 or 4 years generally speaking. I mean, it is RC LiPo :lol:

 

[artvk]

I used aluminium and had them nickel plated using an electrolytic process. Not cheap, but it appeared to work. It leaves a dull grey metallic look, and if you put it under a microscope it probably looks like a stack of spheres. In any case, the layer of nickel meant there was enough resistance to generate heat during spot-welding to take a 0.07 mm nickel tab.
[youtube]jumFyhtjylM[/youtube]

Multiply that about 10,000 times...
[youtube]N6nKPmhSE5g[/youtube]

In the end, the poor spotwelder had done so much work those long electrodes were worn down to a nub, my hands were sore and burned, but I made 4 complete double-sided modules.

more welds.jpg
Nickel plated aly sucks.jpg
20210118_201035.jpg
20210201_174648.jpg
top side welded.jpg

The next step was to coat the welded faces with a thermally conductive epoxy resin and glue a sheet of G10FR4 to it on either side.
thermal epoxy going on.jpg
Module glued up.jpg

End result - a pretty much sealed, waterproof, rigid, robust battery module. The BMS wiring went to a pair of ZEVA BMS modules as 12s units plus four thermistors per module.

" thermally conductive epoxy resin " what brand name you recommend for dielectric one ?

 

[spinningmagnets]

awesome pics! Thanks for sharing all the stuff you learned over the years...

 

[jonescg]

Hi Art,
I used a filled resin from a firm in China. Its a two part mix with a thermal conductivity of around 1.4 W/mK which is typical for these non-conducting resins. I'll look it up.

Edit: The thermally conductive epoxy resin is from a company called U-sheen www.sheenthermal.com And it's product ID is epoxy S8960.

 

[artvk]

Hi Art,
I used a filled resin from a firm in China. Its a two part mix with a thermal conductivity of around 1.4 W/mK which is typical for these non-conducting resins. I'll look it up.

Edit: The thermally conductive epoxy resin is from a company called U-sheen www.sheenthermal.com And it's product ID is epoxy S8960.

Thank you for sharing this ! Admire your built and youtube vids

 

[jonescg]

These are some images of the new race bike battery pack I've built. Only difference between this one and the e-bike battery you see a few posts back, it the nickel-copper-cell sandwich. The Sunkko transformer based spot-welder does a great job. Nickel is 0.15 mm thick, and copper is 0.07 mm thick. Images of the polycarbonate enclosure and air cooling concepts to follow in the next post.

This is 12 kWh (each module is 3 kWh, and weighs 17.2 kg. The port holes were for adding polyurethane potting compound, however I only really potted the base and just used crazy expanding foam to keep the balance wires secure. Much lighter that way.

 

[jonescg]

This is the rest of the battery build in pictures:

 

[peadar]

Stuart Jameson asked me to build a special battery for a unique project - salt lake racer at Lake Gardiner.
View attachment 318615
View attachment 318616
View attachment 318617
One problem with these LiPo cell packs, is that you don't know the exact dimensions of the battery until its built. The cell supplier might assure me they are 7.8 mm thick, but they are more like 8.0 mm thick, and after stacking 40 of them together you have an enclosure which is a wee bit too small...
View attachment 318618

He specifically asked me not to glue the cells in place as he wanted the option of taking them apart. I advised against it, but the idea was it would so a handful of runs on the salt and then not get used for ages, so it was worth the risk.

Very nice battery building,
i am building a 24 s 1p lipo kokam cells 67ah would like to know how you figure out the compression needed, I want to build like you, with polycarbonate,
do you fold the side and bottom seam flat against pouch ?
How do you manage the difference between aluminum and copper?
Thanks

 

[jonescg]

Very nice battery building,
i am building a 24 s 1p lipo kokam cells 67ah would like to know how you figure out the compression needed, I want to build like you, with polycarbonate,
do you fold the side and bottom seam flat against pouch ?
How do you manage the difference between aluminum and copper?
Thanks

There are some research papers I've linked elsewhere on this forum which go into how much compression these cells need, and it's a bit of a challenge to get right. If you used a compression arrangement with limited give, as the cells expand with age the pressure on them increases. Ideally the pressure applied would be constant throughout its whole life, so there needs to be some kind of polymer between the faces of the pouch cells to accommodate the changing pressures. I think Poron was one such material which doesn't collapse over time. The downside is the bulk it adds to the pack assembly, and weight.
I've moved to cylindrical cells full time now, and wouldn't recommend pouch cells for anything other than high performance applications like racing vehicles.
As for the seams around the edges of the cells, my pouches all had a flat base, so standing them upright was no big deal. But I do know that the Kokams have a seam all the way around. I think from memory they use a plastic gauge separator which fits around the outline of the cell, allowing it to be clamped into place without deforming the edges.
As for aluminium and copper - the two don't play nice, so you need to have a conductive grease like Aluminox (Vaseline and zinc powder) between both clamped surfaces. They cannot be welded or soldered (unless it's nickel plated aluminium) so screws are pretty much the only way.
Hope that helps!
Chris

 

[peadar]

There are some research papers I've linked elsewhere on this forum which go into how much compression these cells need, and it's a bit of a challenge to get right. If you used a compression arrangement with limited give, as the cells expand with age the pressure on them increases. Ideally the pressure applied would be constant throughout its whole life, so there needs to be some kind of polymer between the faces of the pouch cells to accommodate the changing pressures. I think Poron was one such material which doesn't collapse over time. The downside is the bulk it adds to the pack assembly, and weight.
I've moved to cylindrical cells full time now, and wouldn't recommend pouch cells for anything other than high performance applications like racing vehicles.
As for the seams around the edges of the cells, my pouches all had a flat base, so standing them upright was no big deal. But I do know that the Kokams have a seam all the way around. I think from memory they use a plastic gauge separator which fits around the outline of the cell, allowing it to be clamped into place without deforming the edges.
As for aluminium and copper - the two don't play nice, so you need to have a conductive grease like Aluminox (Vaseline and zinc powder) between both clamped surfaces. They cannot be welded or soldered (unless it's nickel plated aluminium) so screws are pretty much the only way.
Hope that helps!
Chris

Thanks very much for that, You do nice work

 

[stan.distortion]

Still reading... could you do something on safety? This is a real education, I'm an open source evangelist and even from that angle this is exceptional documentation. In some of those pics you're handling packs in bare hands with rings, seriously well engineered packs and you still have all your fingers, what's the important stuff?

 

[jonescg]

Still reading... could you do something on safety? This is a real education, I'm an open source evangelist and even from that angle this is exceptional documentation. In some of those pics you're handling packs in bare hands with rings, seriously well engineered packs and you still have all your fingers, what's the important stuff?

Haha, yes, I've been known to do things barehanded before and remarkably never had the ring short stuff.
I don't wear it any more
But generally speaking use non-conductive benchtops, insulated tools and wear safety glasses whenever spotwelding, or working on the busbars. Always leave the mid-point buslink as the last to be welded; this just minimises the risk of a full power arc-flash at the sharp end.

 

[bananu7]

Thanks for the writeups. One question that I have in mind, having built my latest ebike box from PC, is how much extra protection do the batteries you build with the thick PC need?

When I made my battery, at first I wanted to use simply 5mm. Then I realized I want the battery removable, so added a secondary inner shell of 2mm thickness.



I feel like that's plenty of impact durability for an ebike, but now I want to house a 20s20p 18650 battery for a motorcycle, and I'm torn between 2mm aluminium and 5mm PC. In your experience, how much extra protection on top of the 5mm for the battery is needed? I keep thinking about adding the secondary shell some distance away from the main battery (mounted on the outside perimeter of the frame), so that it can absorb hits and deflect a couple cm before there's any chance of even reaching the main battery case, but then I'm not sure how thick to make it.

Oh, and a second question; I resorted to using screws for the thick panels just like you did (even before discovering your thread), but my initial plan was to weld them with dichlorometane. This has proven to be a watertight, but not mechanically sound bond. Do you ever add that on top of the screw joints? If not, do you additionally seal the joints at all?

 

[jonescg]

Polycarbonate is great stuff - tough, non-conductive, and you can see shit about to happen, if it's going to happen .
I used screws, but there's no reason you couldn't use DCM to help weld the edges for a mostly watertight pack. I just taped up the sides with gaffa tape when it was wet at the track, which wasn't very often.
It won't be impact damage that causes issues, it will be internal rubbing, chaffing and fretting what will damage the cells. So whatever you do, make sure the cells cannot move relative to the enclosure. Ideally, you'd pot the battery with polyurethane or epoxy, although this does add weight. You can get a 0.6 g/ml resin that seems pretty good for lightweight encapsulation.

 

[bananu7]

Thanks! That gives me some confidence there. Another reason for PC over alu for me is cost; I expect that waterjet + brake bending + tig would run me over 250 eur for the box, while the PC i can cut myself and the total cost will be like 1/10th. For durability, I should've clarified it will be an enduro bike, so dropping on stuff as well as being splashed with water is totally expected and i have to plan for that.

Potting the battery sounds tempting; what do you think about expandable foam (like the one used for building insulation)? Cheap, durable, much more lightweight than any resin. Might compress a bit over time, though.

 

[jonescg]

Thanks! That gives me some confidence there. Another reason for PC over alu for me is cost; I expect that waterjet + brake bending + tig would run me over 250 eur for the box, while the PC i can cut myself and the total cost will be like 1/10th. For durability, I should've clarified it will be an enduro bike, so dropping on stuff as well as being splashed with water is totally expected and i have to plan for that.

Potting the battery sounds tempting; what do you think about expandable foam (like the one used for building insulation)? Cheap, durable, much more lightweight than any resin. Might compress a bit over time, though.

You can see I used expandable foam on the new 12 kWh race bike battery. Not much I might add - just enough to secure the balance wires. But you can get low density potting compounds that aid waterproofing and vibration protection without massively increasing mass. They are generally good at keeping the cells warm when they get hot, since it's effectively an insulating blanket.