Hey there, new builder just wanting to share a bit of photo’s and willing to answer any questions or criticism
Did you add insulation on top of the cell on the positive side? Such as fish paper rings?
No, I didn’t, but the cells have a plastic ring of about 0.5mm, and the cell holders also have a shoulder of about the same thickness. Plus I spot welded the pack very carefully to make sure there were no snags or contact with the negative ring around the edge. I would have shown you the gap if I didn’t tape everything up yet. But it’s always a good idea to put extra insulation rings on, I just couldn’t wait a month for this to get shipped from china.
I think that the biggest reasoning for the rings is that the sharp nickel may pierce the top insulation of the cells, and the rings help prevent it. This may happen during assembly or later during the pack life. It’s probably not a very likely scenario though.
Fully agree, these batteries are insanely powerful and if your not paying attention to every little detail it will go nuclear on your a&@ss. But There is literally an air-gap of about half a mil and two layers of plastic, so im pretty confident in the assembly.
Very clean build!
I have exact combination with my ow BMS. HG2 is Amazing cell. I have 2 0.20mm stack up Nickels to minimize the loss and heat. Plus I have ALU plate on one side of the box thermally couple to one side of the cells with 5mm silicon pads. These cells create some heat when you demand some performance.
I can’t see the bus bats.
I would suggest have one thermistors exactly at the center where heat has less chance to scape (longer path to dissipate)
I have two 5mm by 15mm copper busbars connected to a doubled up 0.2mm ladder strip.
I ran the motor in the pool for an hour on 40% duty cycle “50A” and the cells didn’t go one degree over ambiant, tested it with BMS, infra-red camera and stand alone temp probe.
I’ll keep an eye on them when I start pushing the pack, but so far I’m very impressed with the battery.
What’s the behaviour of the 65161 motor regarding amps, volts and power?
It’s rated 6000w.
If I want to achieve max power how many V it needs?
With 14s or roughly 58V that’s about 103 A.
Will it go to 6000w with 12s?
That would be around 50 V and 120 A.
As I’m planning the battery build myself does that mean that with 14s it is enough for battery to be able to deliver 125 A with about 20% reserve?
Nice pack. What are you going to use for a case?
I’m planning to build a battery from 21700 molicel p42a cells. Debating whether to use a BMS, as they seem to get implicated in fires. The wiring harness of the BMS could cause a fire if the wire snaps or the isolation wears through from vibration, causing a short. Small fuses where the leads attach to the cells is one possible solution. Connecting away from +ve cell ends is another good idea. Having a balancing lead attached to an external plug on the battery case, without a BMS, still has the same potential to short a cell. Flight junkie has fused his individual balancing leads on his subsequent batteries, because of a short on the balance plug that almost burned his battery.
I’ll be using a carbon/kevlar case, still working on the mold.
As for your concerns on the BMS, in my personal opinion, I would rather have something that can monitor my little battery, if you are worried about the vibration you could always secure the wires properly so that they are immobilized.
Do you plan to use bms for discharge too?
I’ve read that this bms has continuous current 120A that should be enough when foiling.
How long it can put through peak current? Will it be long enough for starting?
Once I’ve got the board on the water and running at full throttle ill be able to answer that, for now, my kid’s splash pool won’t survive full trottle. But I’m sure the BMS will be capable of delivering.
and thanks a lot for all about your battery pack.
I want to copy your battery pack for my first DIY eFoil and I just want to ask you if you can post
link of the pieces that you use in your please. (BMS,plastic ring etc)
Thanks a lot again
Ok thanks a lot
I’m un pause for now, cause I wok on a MPCNC the will cut the board
Hi Where did you buy your cells? What price did you pay per cell. I was looking on Nkon and they are selling them for 7.95 per piece. That price is insane!
would advice against having internal balancing. If you are not going for high quality stuff.
Wise to fuse the balance leads out regardless or use extremely thin wires that burn off at >10A
I got the cell’s from a e-sigarette shop in SA for about 7 euro each, not cheap, but in my opinion the best cell’s to use. I’ve been testing the battery hard for the last 6 months and they outperform everything else.