Weird Hub Motor Symptoms

[joeworrall]

Decided to go for a little ride after not using the ebike for a couple of months (blew a charger and it took ages for the new one to get here).. so I recharged the battery and was ready to go. Everything was going great, i had the "ebike grin" again until around 15 minutes into my ride when i noticed my motor making a strange sort of clunking/chugging action that was causing quite a bit of vibration throughout the bike.

I stopped and lifted the back wheel and tried spinning it with no load, it seemed alright so i climbed on the bike again and slightly pressed the throttle, same thing.. chugging action and vibrations. peddled the bike home and checked the phase wires and hall sensor wires, no obvious defects and my motor would still spin without load no problem. It almost seemed like when i was sat on it my motor decided to go completely balmy!

Im really stumped by what the problem is, any ideas??

 

[HighTekBikes]

Since you have a history with battery problems, I suspect that you are hitting the low voltage cutoff of your controller, about 31V. You are getting low range because your pack is unbalanced. The LVC has no hysteresis so depending on throttle position and load, you can bounce back and forth over the cutout point. You can try to measure the pack voltage when it cuts out or right before. This will be a lot lower than the no-load voltage when the pack is discharged. If this is the case, you can do several short cycles of discharge followed by lots of time on the charger to help balance the cells.

 

[dogman dan]

The other possibility is a poor connection somewhere, so check all the connectors one more time.

 

[Ypedal]

I tend to agree with HTB on this one, if the motor runs fine with no load, it's very likely a battery voltage problem..

 

[joeworrall]

Okay so I did a bit of testing and the pack off the charger is 56v (48v pack). The motor runs fine until the voltage goes below around 49v. The pack is nowhere near drained as I only used 1.458/10 amp-hours. The sound it makes is what I would compare to an engine stalling or two plates of metal being wizzed past each other.. Another curios thing is that it seems to run smoothly past speeds of around 15-20mph and it seems the torque is really giving it s problem, obviously even worse up hill. Very strange! Any ideas??

 

[Ypedal]

most likely a bad cell causing the BMS to trip under load.. the full voltage is good, but if a cell or group of cells is having a problem the BMS will trip, when the throttle is let off the voltage comes back up and the thing works again until you hit the throttle again.

if this is happening at 48~49v its likely either a bad cell or a defective BMS. .. if the whole pack was empty you would be seeing 42v or so volts at cutoff normally.

 

[joeworrall]

Hmm, maybe but the lowest voltage reading is 47v

 

[Ypedal]

exactly..

I assume your 48v 10ah pack is made from multiple 26650 cells, usually 3 cells per group.. if one of those cells in the group ( or 2 ) is loosing capacity and draining it's group along with it the pack canot fully charge or fully discharge because the BMS is shutting things down on both ends ( charge and discharge ) .

If the bike runs fine, hot off the charger, the controller is not dead, the throttle works, the motor is ok... that only leaves the battery as a suspect. Only way to confirm at this point is to open it up and investigate ! :wink: ( unless you have a warranty and can have the dealer do this for you )

 

[dnmun]

you don't have to open the pack but you can check the voltage of each cell group by measuring at the sense wire plug on the BMS. be careful with the voltmeter probes and don't short the adjacent cells or you will burn out the sense wire.

write down the voltages so you have record, or have someone write them down while you measure each cell, at the sense wire plug.