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by jonescg
Feb 23 2021 9:54pm
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

It was actually US$500 for 2x10 kg (parts A and B) but the shipping was another US$200.

I think it's filled with boron trinitride, and almost certainly aluminium oxide. 1.2 W/mK and good adhesive properties is pretty nice.
The fillers make a big difference in price, and thermal conductivity :)
by jonescg
Feb 23 2021 4:30am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

It's a product from U-Sheen in China. S8960 as a two part adhesive resin.
1.2 W/mK which is not bad. Fairly affordable too, but minimum order is 20 kg for US $700.
by jonescg
Feb 22 2021 7:45am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

It would have probably helped in this case, but surely the equivalent would be putting one electrode on the busbar and the other on the nickel tab. I did this often and it made little difference to the weld quality. I think in future I'll use copper with nickel tabs. And bigger cells so there's less...
by jonescg
Feb 21 2021 5:04am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

Last module done.jpg 30,000 spot-welds later it's done. A friend came around with a capacitive discharge welder and it was surprisingly bad at welding tabs to the nickel plated busplates. We swapped the two copper rods for the spare hand piece and it simply vapourised the nickel and stuck nothing t...
by jonescg
Feb 15 2021 2:21am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

So I am 7/8ths of the way through this battery build and the last lot of busbars are the worst. They are severely passivated so nothing will stick to them. I found another soldering technique where you can effectively plate the aluminium with copper using FeCl 3 solution and CuSO 4 . It looks like a...
by jonescg
Feb 09 2021 8:41am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 458
Views: 77485

Re: Spot Welding Copper Strips to 18650 Battery Cells

Why might this welder work on .4 mm copper at those settings and the kWeld won't? I'm not home right now but have welded thinner copper using the "sandwich" technique at those energy levels (not sure of the pulse time) but I'm pretty sure it wouldn't work for .4 mm thick stuff. I'm assumi...
by jonescg
Feb 07 2021 1:02am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 458
Views: 77485

Re: Spot Welding Copper Strips to 18650 Battery Cells

Looks great - I reckon it's a winner.

What did it cost you? And how deep is the throat on it? Can you weld up a 350 mm deep pack?
by jonescg
Feb 05 2021 5:13am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

I think all the resin will add about 3 kg to an othwise 27 kg module.

Oh, and I learned this neat trick: https://youtu.be/2rsgbTUxYLE
by jonescg
Feb 04 2021 7:59am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

You answered your own question there :) Too risky to have the busbars cooled directly with air. The tabs are not stuck to the busplates as well as I'd like them to be, so any opportunity for corrosion will only make those contacts worse. Ensuring the heat is uniformly spread throughout the battery i...
by jonescg
Feb 03 2021 6:53pm
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

Yes the thermal conductivity of a cylindrical is 10 times higher in the axial plane than radially, so by focusing on pulling heat out through the ends you can get a very compact setup. The tabs are likely to be a hot spot, so soaking as much heat as possible from the busbar ends makes sense. The pol...
by jonescg
Feb 03 2021 8:30am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

Chris, can you describe the process for encapsulating the cells? Was it hard? What are the thermal properties? (thanks) I've not yet fully encapsulated this module, but the ends have been done with a thermally conductive, electrically isolating epoxy resin. I basically spread out about 900 g of mix...
by jonescg
Feb 03 2021 7:50am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1288
Views: 192904

Re: kWeld - "Next level" DIY battery spot welder

The new cells are big enough and capable enough to need more than a wire bond to complete the circuit. I mean, how long until Tesla decides to use screw terminations on prismatic cells? :wink: Anyway, the bus plate is a solid approach. The issue is how to link the cells to it. I'm left wondering if ...
by jonescg
Feb 03 2021 7:33am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1288
Views: 192904

Re: kWeld - "Next level" DIY battery spot welder

It's a build technique specific to an application. Tesla has been using it to great success with their Model S and Model X batteries, except they have million dollar wire bonding machines. For the DIY conversion, it's a great way to go, provided you can make the interconnects. I have considered mech...
by jonescg
Feb 03 2021 7:15am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1288
Views: 192904

Re: kWeld - "Next level" DIY battery spot welder

Question for the kWelders out there - can you spot weld 0.15 mm thick nickel to nickel plated 1.2 mm aluminium?
How about 0.8 mm nickel plated copper?

Seems like you need all the Joules :?
by jonescg
Feb 03 2021 2:55am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

top side welded.jpg Module glued up.jpg More or less finished this module. One down three to go. The biggest headache is the lousy connection between the nickel tab and the nickel plated aluminium busbar. Wherever the plating surface is badly discoloured it *refuses* to stick. I ended up getting cr...
by jonescg
Feb 01 2021 7:55am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

First side of the first module welded, and now sealed up with thermally conductive resin and a sheet of G10FR4 on the bottom.
first module bottom side welded sml.jpg
first module bottom side welded sml.jpg (185.28 KiB) Viewed 291 times
bottom layer on.jpg
bottom layer on.jpg (123.46 KiB) Viewed 291 times
by jonescg
Jan 30 2021 4:41am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

Wanna come to Perth for a working holiday? 😂 Bring your welded though :wink:
by jonescg
Jan 30 2021 3:38am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

So all 4 modules are assembled waiting on the tabs to be welded. 4 modules at 24s23p means 4416 busbar welds and 4416 cell welds. My Sunkko welder takes about 1 minute per tab cause it needs about 8 zaps, and it gets rather hot. So that equates to around two week work :? Time for a welding party... ...
by jonescg
Jan 24 2021 9:17am
Forum: General Discussion
Topic: Why not heat my house w heat lamps?
Replies: 53
Views: 1405

Re: Why not heat my house w heat lamps?

I have ducted aircon in my house. And the unit works in reverse too. In fact it's more efficient as a heater than as a cooler. It pulls 4000 W at full tilt; that's cooling a hot house down from about 32°C to about 25°C. Split systems are more efficient still, but more expensive to install. The coeff...
by jonescg
Jan 23 2021 9:09am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

Second module ready for spot-welding.
2nd modole built.jpg
2nd modole built.jpg (167.09 KiB) Viewed 386 times
2 modules ready for welding.jpg
2 modules ready for welding.jpg (189.23 KiB) Viewed 358 times
The cover is just placed there, not fixed down. I'm waiting on my thermally conductive epoxy resin to arrive for that.
by jonescg
Jan 20 2021 9:23pm
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

I actually tried that with exactly the same spot welder - gravity was enough to unstick it :cry:
by jonescg
Jan 20 2021 8:42am
Forum: EBike General Discussion
Topic: How much battery capacity is lost annually?
Replies: 11
Views: 492

Re: How much battery capacity is lost annually?

I posted links to research articles on this subject. Should be able to do some work in the search bar to find them. But yep, time x high states of charge x temperature = degradation.
by jonescg
Jan 19 2021 8:41pm
Forum: Battery Technology
Topic: How to handle series connection in a moderately large 18650 battery build?
Replies: 6
Views: 282

Re: How to handle series connection in a moderately large 18650 battery build?

Yeah the maximum current demand of your system is unlikely to ever need that much conductor.
One option might be to solder nickel tabs to the copper busbars and spot weld the tabs to the cell tops.
by jonescg
Jan 18 2021 7:30am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

Bit more progress:
20210118_201035.jpg
20210118_201035.jpg (121.82 KiB) Viewed 465 times
20210118_201046.jpg
20210118_201046.jpg (196.59 KiB) Viewed 465 times
by jonescg
Jan 18 2021 5:11am
Forum: Battery Technology
Topic: jonescg's cylindrical cell build thread
Replies: 59
Views: 2593

Re: jonescg's cylindrical cell build thread

A little progress today - BMS wiring starts to go in. Odd numbered cells first. Then flip, even numbered cells. Then glue the sides on and let that set, then finally spot weld all the cell tabs.
20210118_163001.jpg
20210118_163001.jpg (154.74 KiB) Viewed 472 times
20210118_162939.jpg
20210118_162939.jpg (234.54 KiB) Viewed 472 times
Hopefully by then my thermal epoxy adhesive will arrive...