I have one that does the same thing…Hoping to confirm it is cutting off lower than 80a because it will be going back to bestech for replacement.
I’m getting metr.at bluetooth which will allow me to log my data. Hope this will help me in troubleshooting.
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Let me know!!!
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Whenever I want to know what the cells are doing I connect a parallel balance lead and this guy. It has a neat functionality of showing cell lowest voltage so you can see the lowest sag with ease.
That’s a great find! Shame they don’t do 10s variations. I guess I can use this on 10s, monitor 8cells and then other two on separate ride. Do I need parallel balance lead with this checker? I guess regular balance lead - male to female extension would be ok?
I guess your balance leads are connected to BMS? If yes, you will need parallel adapter first (one goes in BMS, one in meter). If not, you just connect balance plug to the meter.
I your specific scenario you will probably need to make adapter 10s -> 5s, twice. First one for first 5 cells, second one for other 5 cells.
I have Metr, and it’s useful for diagnosing VESC faults. But there is no real way to distinguish between a BMS cutoff and say a remote dropout. I thought my GT2B was cutting out before I built the battery tester/discharger
I hate to say it, but I can almost guarantee it is your 30C lipo batteries. I am in the same boat… It only gets worse from here. I was flying up hills for months, and now even a small incline can trigger the BMS cutoff if my battery is below 75%. My board is crippled until I either buy new Lipos to replace the bad ones, or build a li-ion pack
Well it cant be remote as whole board switches off. Might be lipos but they are new and I only have done around 10 miles on the board so far. Well on my second ride today I didn’t have any cut offs and I did try hard to replicate the problem - went full throttle on same road as before, same inclines. Might have been loose wire or so, I have opened her up and connected everything one again, not sure what was the issue. In couple of days I’ll do some more testing, I might get the cell checker - looks cool.
Btw- I thought Lipos have a lot less sag than li-ons.
So i had this problem yesterday while on a nice little rip. Build is still relatively new. First cut off was up an incline, had to more on flats? Battery (10s) was at approx 35.5 v. I have a Bluetooth mod and ackmaniacs app. Every cutoff would say under voltage fault. From what I’m gathering here that means i could have a faulty cell? Edit: I have a bestech 10s Bms. On a tesla 10s4p battery. I know the batteries are fairly low discharge (10 a constant, 20 for 45 second bursts) but i haven’t really experienced much sag. Defo not enough to trigger a cut out at like 36 v…
what’s your minimum input voltage set to
for the vesc? I still have to get into the tool and look, but i doubt i set the cutoff at anything above 31 v.
Not cutoff, minimum input voltage. If you didn’t change it, it should be 8v
I’ll look. At work right now. Try and do at lunch. If not later tonight.
Other thoughts that are starting to occur to me. Put the battery on charge last night. Selected 100% at 1A. Overnight it should have got to 100 %. Take it off the charger and it’s at 38V. That’s starting to point at me having lost a cell here isn’t it?
you gotta measure every parallel group to see what voltage they’re all at
Ok. Stupid curiosity… should be working and here i am ripping apart my board haha. 
- 3.59v 7. 3.59
- 3.68. 8. 3.67
- 3.62. 9. 3.67
- 3.65. 10. 3.67
- 3.67
- 3.67
Not sure what the tolerance is but doesn’t look terrible to me…
not terrible but also not balanced, my deviation is normally within .02v
like would you say the bms isn’t working?
Could be, or a parallel group isn’t fully connected. Try measuring each cell of the outlier groups (1st 3rd and 7th) and make sure you probe as close to the cell surface as you can.