8 by 0.15 is aprox 1.2mm2
copper carrying 19 amp ish will be at 70deg c in a air temp of 35 deg C and coppers a much better conductor than Nickle 3 and a bit times better.
You rate Battery packs according to its weakest point. 1 little Nickle tab is a week point it adds resistant that heats up. To much heat is just bad for electrics and battery’s and carying current, voltdrop. Down to a balance of how much heat and reduced life you think is acceptable.
it seems 7mm wide is kind of a standard size for 18650 but you could use 12mm and .3mm thick.
copper is over four times as conductive as nickel
it would be nice to do a simple test putting current through with a power supply on the bench. I think the standards here (https://endless-sphere.com/forums/viewtopic.php?f=14&t=68005 ) are pretty conservative as well as matador’s. there’s the big variable of how long at the current and also the ability to get rid of heat. of course lower electrical resistance being the better performer beyond the safety concerns and better just to go bigger
It seems everyone is way under spec on these tabs and maybe people are following in the footsteps of ebikers where they generally aren’t pulling as much per cell, and cells are getting more powerful
extrapolating from niobie’s guide I posted a 12x.3 strip would be considered good for up to 16amps and acceptable up to 25amps.
All these ampacity charts you guys posted, why doesn’t it mention the length of the wire/nickel strip in the data?
so 20awg is good for 10 amps? but over what length? a metre?
What happens if you are only using 5cm? can you pull 20 amps over a much shorter distance? these charts make absolutely no sense without knowing the length of the wires.
Did some current testing with the pcb only, put it in series with my 12s5p battery pack on my mountainboard went riding in grass for 15 minutes, wasn’t able to get heat in the PCB
As expected Bestech did it right
The final nickel is not yet ready but will test that on high current aswell. But I guess that won’t be a problem aswell.
I knew it was a collaboration but dident realize they had the rights to sell it as well. I’m pretty sure the $27 that there selling it for includes the nickel and battery holders. Also why .3mm nickle? Most welders that people have can’t do .3 nickle.
It’d be cool if the holes the nickel goes through allowed a couple more layers of 0.2mm nickel strip… maybe even a mm or so extra so we can layer more nickel on the cells, down to the traces, and a solder some loose (keeping it flexy) flat braid across the pads to really up the ampacity of the board for 4P with 35A cells like VTC5a for 140A and minimal sag/heating.
I’m confused looking at the pics. I guess they decided on the one long trace coming back, probably safer, but to me it looks like that long coming back trace is really only on the one side as its a disconnected trace w two balance traces cutting it on the other side. and there aren’t any vias to connect the two sides anyway. Am I missing something?
