So guys, background. Only recently has this started. Went out for a ride the other nite with 70% battery, I only managed 4-5km. I should be getting 20km at least.

Noticeable issue: one motor spins more than the other which leads to believe the motor is dodge, bad sense wire/circuit possibly. Plus it ticks on spinning and whines alot on rides recently.

The mobile vesc tool app always shows 100% battery regardless of the charge! No idea why.

I have not checked any P groups on the battery yet, possible issue here? And chime in folks if you think it might be.

Any thoughts guys? Cannot recall any major incidents on previous rides that would cause these issues to manifest.

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Check p groups asap. Sounds like you might have a dud.
Also that Motor has a fucked bearing most probably. Try blowing it out with compressed air or something to clear debris

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Will do.

Re:the motor I have done compressed air. Did not see and debris or loose magnets. Bearings seemed fine to my touch.

Try the continuity ntest?

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It’s probably set to 3S which I think is the default. Change it to 10S

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Disconnect that motor, ride on 1 motor (yes, the performance will be less) and see if you are still having the same problem

If so, it could be the battery or BMS

If not, it could be the motor or ESC (then swap which motor is on each ESC)

But there is also a scenario where it’s the battery or BMS but the problem doesn’t show up under a lower load.


Great tips guys. Thank you much. I will try these out and report back!! Your not a bad bunch really🤪

So some small updates. I noticed one dislodged series tab on my battery pack so I stripped the pack and re spot welded the offending tab. When the pack was out I installed my smart BMS also. When connected to the BMS I can see that the same ‘p’ pack with the loose tab is well down on the voltage compared to the rest of the P packs. See below:

Now, being a novice with Smart BMS. I am confused as to how the thing knows when to allow charge because when I connect my charger nothing happens. The BMS is wired for charge only. Does anyone know what’s setting to look for?

Took a test run around my garden this evening and still getting 100% battery showing after setup in vesc tool for Windows.

This should be reading 80%.

I also changed the bearings in the rough sounding motor I mentioned earlier.

Still confused as to why this happens. The investigation continues

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Ok so got the smart BMS charging and setup, I think. Charge the pack and p 9 is showing low voltage. So I guess the bank is bad? Right?

Probably it became unbalanced due to the broke weld

Let it balance fully before riding, with that much diference and all cells being way higher it will probably take a few days, you can also charge that group using another charger to speed things up

After that go for a ride, if they stay balanced it’s all good, if one of them drops again and all connection are good this group is bad, if you don’t have that much cycles on the cells you can just replace it


So after a good few days trying to get the battery pack to balance P9, it still does not want to balance out.

My smart BMS settings:

Maybe I have overlooked something here? Noob as far as Smart BMS goes…

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Depending on how many cycles are on the cells, I would either replace the P-group if the number of discharge cycles is really low (under 10) or I might just convert it to a 9S6P otherwise :man_shrugging:

You could try charging just that p-pack by itself as mentioned above, but if it becomes unbalanced after a ride (when it was balanced before the ride) then that p-pack is bad and needs omission/replacement


Oh no, it’s balancing out, you went up almost a full .1V its going to be slow. Really slow. It you have a lipo or 18650 charger you can use to throw a full amp at the cell and get it much closer the bms can do the final balancing. But you’re waiting for it to balance in miliamps I think.



@MTB2019 I’m assuming from the the latest map video that you got the pack balanced. Nice.

I was having a similar problem recently and wanted to drop some data here so that others looking for balancing info could find some hard numbers.

  • My pack is relatively new, uses (48) Samsung 30Q cells in a 12s4p configuration.
  • I use a Neptune 15 BMS which handles the charging and balancing. Conveniently is has an Android app for monitoring.
  • The BMS is wired as charge only since I pull more peak amps than the BMS can handle
  • The BMS settings before the event:
  • 5 Hour charge and balance time (before a timeout)
  • 50mV delta for all P-groups (it will continue to balance until it hits this delta)

On August 27th, at about 4PM I noticed that my battery had a P-Group delta of ~350mV (yipes):

I had no idea how the pack had become so unbalanced. I searched the forum and found this thread, which helped give some perspective on the lengthy times required to balance a pack (without charging a specific P-group using a standalone charger)

Taking this into account, I changed the BMS to:

  • Use the maximum balance timeout (18 hours)
  • Shrank the p-group delta to 30mV (to help keep the pack more aligned)
  • Started the process of balancing the pack

I may have missed a few hours here and there (as I restarted the balancing after hitting a timeout), but between 2020-08-27 ~8PM and 2020-09-04 ~8PM the pack was actively balancing. Here’s the results from after the balance completed:

This means the balancing process required ~192 hours to move from a ~350mV delta to a ~30mV delta (~320mV change). This means that to move the needle 10mV required about 6 hours.


After the pack balanced I charged up to full (which for me tops out at 4.1V/group) and went for a long ride. After the ride I checked the resulting pack balance:

The pack remained balanced throughout the discharge (which was a relief). I have since run through a couple charge / discharge cycles and the pack has remained in a balanced state.

Interesting thoughts on the data

Note that the ~350mV delta was the largest difference, but half of my p-Groups were unbalanced. This appears to essentially be a worst case scenario where half the pack needed to be brought in line with the other half. Based on this I would say the balance time I note here is probably the longest expected for this configuration. I imagine that larger deltas, or higher parallel cell count would result in even higher balance times.

For me, the lingering question remained, how did this happen if my pack is healthy and I have a good BMS?

From the results, I would conclude that the 5 hour charge and balance timeout stopped the balance cycle before the pack was done balancing. After several charge / discharge cycles this resulted in an ever increasing delta between the groups, until the pack arrived at the 350mV difference. Increasing the timeout seems to have addressed this issue, which I think bolsters this conclusion.


The P9 group appears to be behaving since my last ride above plus a full charge on return after my ride. This took a few weeks to sort out, by charging the pack and allowing the smart BMS to static balance during the time in between the next charge. What I could see happening was the pack was discharging to reach the the lowest group value, in this case P9. Then I would charge again and repeat until P9 came up to respectable value in line with the other P groups etc. Whether what I done is correct is for more knowledgeable people than me to call. All I know it works.

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Resurrecting an old thread. So P1 group had bad cells in it and has now been replaced. However my LLT Smart BMS is not charging and does not appear to be balancing out the P1 group.

When I say not charging it charges for like 3 seconds and then stops. The app shows charging then not charging on the toggle button on the dash screen etc.

BMS gone faulty?

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I recently had this problem

This is happening (at least in my case) because you’re triggering one of the safety features of the BMS.

In my case, i removed/disconnected the temperature sensors before I turned off temperature sensors in the app.

So my BMS readed -30° before I turned the sensors in the app off. The thing is, that the value stuck on the BMS and would trigger temperature protection always.

To solve it i installed back the temperature sensors, turned them on in the app, got an accurate reading, turned them off in the app, and disconnect them again.


Tried this and didn’t work. I shave a Daly BMS I will test that and see if it works then. I have another LLT Smart BMS on the way. As backup.

Ok so I got replacement LLT smart BMS yesterday and hooked up today and it’s charging but pack 1 is not balancing.

Fucking pain in the face!