Got the case built for the battery. Hooked up my custom BMS while charging for balancing but it didn’t need to do much at all.
None my glands could fit though the 1/2 inch acrylic so I drilled holes, sanded sharp edges, put a ziptie on the wire inside for strain relief and siliconed the wires in.
Might try and find a better solution in the future.
Added the top with vhb tape and a 1/4 inch piece.
Going to try it out this weekend!
Good work brycej, looks tidy. Could you countersink the holes to fit the cable glands?
I used 4.5mm polycarbonate, which allowed a couple of threads of engagement on the lockings with PG9 glands (w rubber seal removed). Polycarbonate is much stronger than acrylic, and easier to drill without cracking. Adding some extra strips of polycarbonate in the corners allows plenty of glue area and stiffness. They make a very fine angled polycarbonate trim strip which I used along the long edges, and to provide a wider seal area for the lid.
Couldn’t you use the cable gland in a drilled and tapped hole without the nut? I often do this in thicker aluminium. depending on the gland size it might be a pretty common tap (M12 or M14)
Great idea @npak! I do have a tap set and I think I have that size.
@Jatem if i had my CNC up and running I probably would have done that.
I was pressed for time to get it done. Currently camping in SD and had a great kite foil session on the Missouri river this evening! If there is wind I still would rather kitefoil then efoil. Might try for a dawn patrol session tomorrow before we continue on the road. I want to compare the new 14s vs the old 12s!
Two soldered 6S10P 21700 batteries. 0.45 mm copper sheet used for bars. 80W soldering iron is enough for this job. Many thanks to funboards.at
I’m looking forward in building a 12s12p battery with 18650 cells. What size of nickel strips should I buy? Will 0.2mm x 8mm heat due to resistance?
Thanks for sharing! Soldering the batteries especially with that amount of surface area is really hard on them. I would expect to lose some life/capacity. There is a reason why any professional pack won’t have any soldered cells in it.
There are a few people around here that solder fuse wires for protection, but I wouldn’t even do that personally.
My quick search didn’t turn up too much actual data, so maybe it isn’t as bad at I think…
0.2 mm x 25mm or maybe 0.2 mm x 20mm. Can’t remember the ideal size for 18650. The wider strips is way way easier to work with, less error prone, better current!
I used 0.2 mm x 25mm on my diagonally connected 21700 and it fit but 30mm would have been slightly better.
It’s much better to use a wider strip so you don’t need to stack strips. Using smaller strips for serial connection will be a bottleneck so use wider strips as Brycej is doing.
Do minimum four welds on each end with 18650 Don’t weld/solder in the center of the the negative side.
Hi! How can i get all my cells on the same voltage so I can solder them together? And what voltage difference is okay?
(I’m going to build a 12s12p battery with 18650 samsung q30)
what voltage difference is ok ? i would say 0.1-0.2v never find a answer on that, so i grad 3.2v cell and a 4.1v cell (30Q) put them in // and measured 0.7A of current between them (delta 0.9v)
but i didn’t weld 12 cells together like that, and if it’s done i didn’t think you can know the current flow during the time your row balance itself, eventually measured heat?
i will stick to 0.1-0.2v just not to worry even if i think we can go higher (on good cells with low IR)
and this is not a problem at all, what is pretty scary is taking a battery a part and pull the spot weld on + ;), so do it really nice the first time and think about all the wiring, solding, bus bar, balance wires before spot welding
Yeah I agree with @Alexandre probably .1 or .2 would be best for the batteries.
Worst case for the battery would be all the other batteries in parallel charging the one you put on there. 30q has like 22milliohm according to mooch plus some nickel resistance… Let’s say 30milliohm and if you didn’t want to briefly “charge” it more then 6 amps that would be. V = I * R =>. .3*6 = .18V
That 6 amps would quickly drop as so it probably wouldn’t be too hard on the battery.
i agree with you @brycej , but i never found the same IR on the cell, depending if it’s given on DC or AC courant testing
RT= 1/ (1/r1 + 1/R2…)
so i did the test and never saw 6A, i never saw more than 1A, and i do that on old cells for my vaping, the cells will slowly get to the same voltage, not heat
So i am missing something here
this formula works to found the IR with the voltage drop on a constant I(A) applied, not sure what to take in account since the highest voltage cell also have a IR?
between 2 cells put in // is it the voltage difference with R/2 ?
