Pics bruv! We need more battery porn in this thread
1 Like
Those welds arenât as strong as Iâd like. They should rip the nickel like this:
and leave little sharp pieces of nickel left behind attached to the cell.
1 Like
Your feet can handle 100 miles in a day?
1 Like
I think you gotta do 20 miles standing then 10 sitting at a time
1 Like
Weâll find out, most Iâve done is 65-70. Bigger question is if my liver can handle it, but i have a trick for that, alternate real beer and NA beer
Theres a big OW event 35mi away, and a crew of us are riding up there.
2 Likes
Thereâs no single âcorrectâ way to find a bad cell, it depends on the time and equipment you have.
You can measure their capacity, discharging them down to 2.5V at a 0.2C rate, and comparing that to their datasheet rating.
You can measure their DC internal resistance using something like the ProgressiveRC ESR meter.
You can test their self-discharge rate (how much they drop in voltage after charging and then sitting for at least a week).
Any of those tests can start to find the cells that donât perform as well as the others but doing all three tests is best.
5 Likes
The dud packs I got have been sitting for several weeks to months(still welded together). Could I pull it apart as is and see a difference in the cells now, or should I charge it again and then check?
If you recorded the at-rest voltages (at least an hour after charging or use) before it was left to sit then you can re-check now. No need to take it apart to test for a leaky p-group.
Otherwise thereâs no need to recharge as long as theyâre up near fully charged voltage (to speed up the self-discharge). You can test the p-group voltages now and then re-check at least a week from now. A month is much, much better though.
If you want to test individual cells then youâll need to disassemble the pack, charge all the cells the same way, let them rest an hour, measure their voltages, let them sit for a month, and then re-measure their voltages.
1 Like
While i do I like this. and it is probably simpler. I think the low voltage start/end based of of min cell voltage idea would be better turn down experience. though it requires more bms cooperation. so both are interesting ideas.
1 Like
Just finished up my first brick pack. I didnât have access to a spot welder (the one here at my schoolâs EE lab broke) so I used resistor legs as cell-level fuses, moving really quickly to heat the cells as little as possible. Anecdotally, they didnât get noticeably warmer than they had when I tried spot-welding earlier, and I actually some fuses blow during a test run (with a worse enclosure) after one of them broke due to mechanical stress. I know itâs not really in vogue on this forum anymore but Iâm pretty convinced itâs a good technique if you donât have a spot welder.
5 Likes
For sure. My idea was more about how the issue is detected by the vesc , not how the rider is alerted. The alert could be anything.
2 Likes
yeah but you get the distinction? with the vesc seeing individual cell voltages it can âdetect the issueâ much sooner ie at itâs low voltage cutoff start(/cell) value. so it can slow down gradually as weâre used to.
Only using the binary signal from the BMS means detecting the moment undervoltage (or other fault) occurs. at which point to signal back to the rider you have to do something more dramatic. can still be smoother than just cutting off though.
thus i think both paths are interesting.
1 Like
I mean itâs not great, but itâs slightly better than soldering a 12awg wire to each
Itâs like, you wouldnât be as mad stepping on a bunny poo, than stepping in a cow pie. yknow?
That aside, the rest looks cool
1 Like
should have known Iâd get roasted coming in this thread 
still proud of it for my grand budget of $0
1 Like
Hey - I said the rest looks cool
2 Likes
2 Likes