Glob of hot glue was just torn off of the balance connector. I had wrap over the ends. Took it off to probe things.
Assuming makes an ass of u ‘n’ me.
And so far with the pics I’ve been uploading I’ve already spent more time taking pics than actually doing any work. I’d rather accomplish more and share to social media less. I’m here to learn not doxx myself.
Flukes are nice but really overpriced. You can get comparable meters for 1/2 the price or less. I’ve got several of these at work and tbh I don’t see the need for anything better. Both current inputs are fused, it’s auto-ranging, it’s got reasonable precision, they’ve stood up to years of students doing student things with them. I’ve seen a student try to measure current in parallel instead of series with 5000V lower current power supplies, arcing the fuse after it blew and somehow it survived. There is a big step up from a $12 dmm to something like that and a very small step up from something like that to an equivalent fluke that costs twice as much.
Sorry for the rant, but I’ve got opinions on multimeters.
With the rest of the groups in the pack testing all above 4V this one should be close enough to balance out right?
What voltage is this new group at
why is this uninsulated xt60 sitting on top of a metal bms
As mentioned above they’re Pricy Bois, I’m in the same boat and as soon as I get my first engineering pay cheque in a few months my buy list is a Brymen DMM and a proper lab supply. EEVBlog on YouTube also has some good roundups of more budget offerings, his standards are pretty high (and sometimes a little weird) but I like the vids
All cells at 4.16V going in as read by a Nitecore D4
Group is currently reading 4.112V from nickel to nickel as tested on the DMM.
I also learned that I have a 400kOhm resistance from one hand to the other, presumably through my heart.
No no do not! Continuity checks are only good on a circuit with no energy source and when you’re sure the storage elements (caps + inductor) are discharged, ie never use on a battery
I wouldn’t expect the bms to fix a whole 0.15v personally
What 0.15V? Between this group and the rest in the pack? Should I connect each group to the charger individually until they’re all within the smallest margin of eachother, then discharge and charge the pack?
If I was doing it, I’d likely try to discharge the new pack to match the others
I could solder on a wire and a connector and vape on it lmao. 16000mAh 180A vape battery lmfao
I wanted to use Velcro straps to hold the battery, would it still be possible?
Hey guys I need some help with the LLT app, i can’t figure out what parameter i need to adjust to make my pgroups charge to a maximum of 4’05V.
I want to reserve that last % to lengthen the life span of the battery or for when I need a full charge bc of range or power.
I tweaked the parameters i thought I needed but when I charge it still goes to ≈4’2v (a little less).
I would send screenshot but untill tomorrow I won’t have my board at hand
Yup, to give a bit of an explanation of what (may have) happened: with a bad or intermittent spot weld you are effectively running the last S group in 2P, and the rest of the pack in 4P. So you’re drawing 2x the current every km from that group than the rest, and it will discharge more than 2x as fast [1]. You’re also (I think) running a discharged BMS, so the only thing that determines when the ESC shuts off is total pack voltage. This means you could be at (11)x(4.0V) + (1)x(1.0V), and still be wayyy above your full pack cutoff of 42V, so the ESC absolutely murders those cells.
I reckon you didn’t have a fully nonexistent weld, or this issue would have come up on the first cycle. It was likely either weak enough to mechanically fail after some use, or it’s still there a little bit but just providing a much higher resistance than the others. In delayed mechanical failure you have a perfect pack then a weird 11S4P + 1S2P pack that yeets itself on the next run. On imperfect high resistance welds, you have a progressively more uneven discharge in that P group, or a pgroup where it can take a low charge current ok but not a high discharge current. Much of a muchness really
[1] Running cells harder (20A per cell vs 10A per cell) generally gives you more than a 50% reduction in run time because resistive losses are proportional to the square of the current - ie they’re exponential. Battery stuff isn’t quite resistive losses, but it’s pretty close. See some graphs from Mooch of a cell at 5A, 10A, 15A, etc to show that you don’t get an even 60 minutes, 30 minutes, 20 minutes run time. Alternatively, see that the capacity graphs get lower and lower, ie current-time (mAh) is nonlinear
The cells were still connected, but weakly.
I’m running the pack in direct discharge with the BMS pulling charge-only duty.
This is what it reports now.
To me everything looks good but group 11 seems to not be balancing, is the grey an indicator of a missing balance lead?
No I think if it was missing a balance lead it wouldn’t show anything, and the other group attached to that lead would be wrong too. Grey looks to be undercharged, green is good, and red is over
The red cell jumps around between the highest charged groups. Group 11 looks stagnant and grey.
Don’t weld in the center of the negative end
Yup I always try to avoid it. This pack I added 2(4) more welds to each cell though because paranoia
