Certified FOCBOX Suppliers | Focbox Unity 4 Day Sale

High Power 10s Lipo Battery Pack with BMS


Hi all,

had a couple quick Q:

  1. I assume the eswitch wiring doesnt matter (no + or -) as you are just creating loop?

  2. Balance cable wiring- I noticed on primary battery pack (+) you start off the balance cable wiring with the red wire in slot 12 for a 12s set up. I noticed on my diagram and @Namasaki on the last battery the red wire is going to BMS (while ignoring all the grounds) on other set ups i see people skipping the last battery red wire and then using the last ground to run to BMS? A little confused by this.




  1. That is correct

  2. The first cell in series provides the negative main.
    The last cell in series provides the positive main.

The balance wires start at the first cell and count up to the last cell.


So here is what i came up with. Starting from left to right first red is b12 then b11-b9 (skip last black wire from battery grnd? Also since jst ext is 5s i would skip the last two black wires and then start the next battery red wire in b8 same thing to b5 then last battery red wire b4 and same thing down to b1. Do any of the balance wires go to b- on the bms or just the main neg from battery?


The red wire is always the last cell in series of a pack.
So the cells count down from the red wire but the last wire or the wire furthest from the red wire is always ground.


Thanks @Namasaki. I think I have it now, sorry my description wasn’t too great. I am skipping all the grounds on the lipo (furthest from red) as well as the 6th cable on jst ext. Red (+) wires will be on b4, b8, b12. Last question (sorry appreciate the help don’t want to screw this up) I don’t need the final ground to go to b- on bms right? Just the negative of battery to bms not both. I saw mixed ways of doing on youtube.


It depends on what bms your using.

Ok, I see your using the same bestech that I used.
With that bms, you don’t need to use any of the balance ground wires.
Just run the main ground cable from the first battery pack in series to the B- pad
as shown in my diagram.
That bms uses the main ground instead of the balance ground wires.


perfect…thx dude!


So am I right to conclude that if I leave my board on with the charger unplugged it will balance the battery at a lower voltage than 42V? (for example also at 39V for a 10s setup?)
If yes, how long do you leave the board on?
You said ‘‘let the cells balance down’’, does that mean the voltage of the whole pack will drop slightly when the BMS balances the cells?

And another question: do you trust the switch to turn off the board completely or do you still plug out the battery over night?


Your batteries really should be balanced before connecting them in series to the bms.
The bms trims high cells down to match the lower cells when balancing.
From my experience it appears to do this even when the bms is off.
As far as balancing the cells when the total voltage is below 4.2v per cell, I have not done a conclusive test to prove it however it does appear to do so.

The built in E-switch is adequate for turning the whole board on and off.
I have left my board’s sitting in the closet with the battery connected and the E-switch off for more than a week without adding charge to the battery but checking them periodically and they are holding their charge very well.


This is an awesome thread and just wanted to thank @Namasaki for all his help both in this forum and directly through PM. I have one last issue i am trying to resolve been talking to jens @Nowind as well. Dont see a great forum for this and too many new topics started so figured i would ask here. Hoping someone can help. I will share a video want to get your thoughts of what noise could be. In bench test it seems to be coming through both motors so I am not thinking defective but maybe you can lead me in right direction. Noise happens about 1/2 throttle or more and also when coasting from time to time.

Set up:
Dual vesc 6 in bldc hybrid mode
Settings are well below what motor can output
Checked for loose screws etc

Nothing so far.

Youtube link:


Other thought is could it be the chain and maybe too tight?


Try FOC. FOC will eliminate noises from the motor. Thos way you can see if the noise is mechanical noise from the drive train.


thanks Frank but FOC wont work at all…i have tried to configure at least 10 times (no exaggeration) each time wiping vesc w firmware update and starting from scratch… the behavior is bizarre. Sometimes, only master vesc will work and inverts direction of wheel, other times both wheels spin in right direction but just go full throttle and lose connection. ThenI have to wipe vesc and go to BLDC hybrid to get to work again. If it try to go back without wiping vesc crazy stuff happens in BLDC mode as well. FOC seems totally unstable for some reason. Just talked to my motor head friend who works on motorcycles he suggests

Chain too tight causing lateral torque
check bushings/inner motor for vibration/markings
check motor mount and cog/gear alignment using laser
balance tires on a spindle

so guess i will try that. If anyone can explain the FOC madness happy to listen and try again.


It inverts direction because one motor is pointed to the left and one to the right. There is option in vesc tool to invert it so both go the same way. Try to go FOC one more time, invert one motor, configure CAN, properly configure remote and tell us what happened.


Do single motor, single VESC first. Test each VESC with each motor.


And try without the sensors plugged in.


Thanks @webst I def know of the inverted option i have to click it each time in BLDC hybrid for the slave to invert. I have Photon remote so I cant config per se. I set to UART, 115200, in nunchuck tab control mode= current w no reverse then i config in remote itself. remote hasnt been an issue at all in bldc once i got it up and running so shouldnt be that. @ trampa i have always done one vesc at a time and they both work that way. Problem is when i connect them either both spin in right direction at full speed then dies out or only master spins i can usually control for a few brakes/revs then that revs up and dies out. I do not have CAN connected until the slave config. I have not tried without sensors connected.


how exactly would i do w/o sensors should i still select hall sensors during motor wizard despite them being unplugged and I would assume the motor resistance and flux linkage do not need sensor to calc? When do i plug in sensors and what settings would i manually update in config.


Only CAN L and CAN H connected I guess. Some managed to connect all four pins…

I would do the detection with very loos chain. I would compare the values the same VESC measures for both motors. Then do the same with the other VESC. Especially the resistance and Lambda are of interest.

This way you can see if one motor or VESC has a problem.
Bench tests do not give a lot of feedback, since VESC use current control.


Just unplug sensors and omit them in motor detection wizard. Do not plug them now and tell us if it’s working.