Conductive epoxy/glue a piece of copper sheet on top?
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if you were going for āgoodā connection then just plain screwing/flush rivet it on would be ideal I think.
Hi, is it safe to weld a group of six 21700 batteries this way: anodes soldered with nickel, and cathodes soldered with nickel and connected with 1 or 2 8awg wire. Without going into details, this is a configuration I am considering due to space constraints. Thanks
Hey there fam!
2 weeks prior i had a quite serious crash, broke my elbow into nice little fragments, anyways, the cause of the crash was the battery. Seems like i didnāt make it good enough. Some problem slipped in, but i cant figure out the cause. I was monitoring the temperature, all the data, everything seemed fine.
After several full throttle accelerations to 50km/h i got the balls to do 60, the board just cut out and sent me flying.
I was logging the run on my phone, ill attach the files. Interestingly the log stops about 100 meters before i crash. Everything seems fine to that point.
At that day in the evening i checked out my board and the bms showed balanced cells and the vesc was working.
Fast forward 13 days, i got out of the hospital and got a chance to turn the board on - and nothingā¦
I measured 3.7 volt across the main terminals, with the balance leads each group showed about 0.3 volts.
No visible damage on the battery and no funny smells, but i will pull it apart for good measure when im fit for it.
What could have caused this?
Anyways, ride safe
cheers!
2023-06-08_14-28-36.csv (927.9 KB)
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You should NEVER solder directly to a cell. There is no safe way to do it. The heat from the soldering iron will damage the internals of the cell, and potentially cause thermal runaway or an internal short-circuit. It can also cause damage that might not appear immediately, but can increase the risk of your cells exploding sometime down the line, even if your pack āseems to work fineā in the meantime.
If you search this thread, you can find tons of discussion about just how bad of an idea soldering to cells is. Please dont do it. The proper way to make connections to cells is spot welding.
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Thank you for your advice. I never said I am going to solder directly to the cells. The pic is to illustrate the orientation of the cells.
Sorry about the elbow, that sucks. Hope you got some good gear on the way for your next slide, hindsight right? 
could you have hit a fault limit or something? Canāt open the cvs so you got any screenshots or telemetry?
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true.csv (823.2 KB)
You are right, i will be buying some fancy ass protectors in the future.
Ive attached a copy i made with the vesc tool, not sure what you want to look for, if this doesent work ill send some pics.
altho im more curious about how my battery got ran into the ground in two weeks time from 70%
is it possible to revive a battery that is at such a low voltage?
No, and if you want to know whyā¦
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If you donāt have your āShutdown Modeā set as below, itās easy to forget to not shut down your controller which would lead to what happened to your battery.
In any case, Iām not convinced this issue was caused by your pack. Iād start a thread to troubleshoot including whatever logs you have. Would also be useful to post all of your VESC tool settings as well.
What esc are you using?
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Nope, nope, nopeā¦check out that video.
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In case its not obvious this is made/marketed for upgrading Razor products like a mx650 bike and maybe Crazy Carts or something.
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Looked decent. Actually, for a China pack it looked great.
Definitely donāt need those wires to be the same length as the couple of micro-ohms difference in their resistance means almost nothing for their current sharing. Though my OCD really prefers to see them all the same length. 
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I had that setting at 30 mins, I guessing it might didnāt work.
Makerx dv6
Hmmmmā¦ it should have. Tbh, Iām really not sure what could have caused such a significant drain on your pack ober the course of 2 weeks. If memory serves, you built a 12s4p P42a pack? If you were at 70% battery thereās no way a parasitic drain could account for that amount of energy being bled from the pack.
Did you use and LLT smart bms? I think there were some bunk units that were draining batteries at a higher rate than normal but stillā¦
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Llt, but before the board was ready the pack was sitting for a good 3 weeks or so, drained about 20-30% percent.
It really is strange.
I want to use a laboratory power supply to revive it but if itās a problem with the pack it might turn into a big pile of ash
Sounds like a bad bms. Did you purchase your cells new? From which vendor?
You can revive the cells but the pack is no longer suitable for high-current applications like esk8. Most I would use those cells for is a flashlight. This is how batteries go boom.
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Nkon EU
Thatās a bummer
Why is that?