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Power cuts out under certain circumstances.

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    Power cuts out under certain circumstances.

    So I used my ebike consistently for 9 months or so, then I didn't use it for 3 months. Now it is doing something strange. It works fine for up to 4-5 miles but then it just cuts out, full power off as if the battery were clicked off. If I click the battery on/off and reboot, it works again for a few minutes. Then if I do it again, it works for a few seconds. Then it just doesn't work. I've checked all the wiring on the battery and it doesn't seem to be the problem. I removed the brake cut off cables and disconnected the pedal power clips. Nothing looks wrong leading in/out of the controller. I opened up the throttle case and everything looks OK visually. No corrosion, loose wires etc. I just ran a test to make it happen and it did. The battery is still showing 39v (36v nameplate). No clue what this could be. The only thing I haven't opened up is the control box itself and the motor.

    Could something be over-heating? Has anyone else had this problem?

    It's a cheapo ANCHEER from China but it was working just fine and now it's not. Any guidance would be greatly appreciated as it is my first e-bike.


    If I were to hazard a guess, you have a battery problem. the 39V measured under no load is not that meaningful as the voltage drops when loaded, probably below the LVC. As I say, just a guess. but is the 1st thing I would look into.


      Was the battery near full discharge when you shelved the ebike for 3 months, or did you set it aside with a full charge? Maybe one or more of your cells discharged so much that it is no longer able to accept a charge.

      It sounds to me like the problem you are having is tripping the circuit breaker in the BMS. I would guess that your ebike would work for many miles if you were only drawing a small amount of current. Maybe as an experiment you could go for a slow ride making sure to draw only a small amount of current for the whole ride.

      If it is the case that your battery is unable to provide a "high" amount of current, this could be indicative of bad cells or a bad row of cells.

      FYI I have a battery with a bad row, and I just baby that battery (i.e. I use it on short or slower rides). This "sick" battery does fine discharging up to 23A or so (depending on the charge level), but it is incapable of providing large amounts of current. It is a 10s9p, and one of the rows has 1 or more bad cells in it.
      Last edited by commuter ebikes; 09-08-2018, 08:08 PM.


        Hey, thanks for the input!! I don't remember if it was charged or not. The theory that the voltage drops under load and that trips a circuit breaker certainly matches the behavior. It always seems to konk out when I'm at a lower speed and then I put the throttle on full. Also, I had it on a rack and had the throttle at full with the wheel spinning and it went like that with no problems, apparently because the motor wasn't pulling much because there was no load.

        f I open up the battery and test each cell individually with the voltmeter, would I be able to tell if one of them was bad? Should I not bother and just buy a new battery? I don't really have the experience and time to rebuild the battery.

        Thanks again! I wish I had found this forum earlier!


          I would recommend an easy first step of trying a 100% balance charge over night.. Your 36 volt battery should come close to 42 volts when fully charged. And leaving charging (in a safe place) overnight will allow the BMS to balance charge the pack. Hopefully bringing the low cells up to the voltage level of the higher ones.

          Read this...

          See my completed Magic Pie V5 rear hub motor E-Bike build HERE.


            You could also try a full discharge (long, slow ride until the LVC kicks in and then pedal home) followed by a full charge.

            The behavior that you describe does sound like it trips the circuit breaker in the BMS as a result of trying to pull more Amps than the battery is able to provide.


              Thanks for the advice. I ordered a new battery. Hopefully that does the trick. If at some point, I have the time/energy to open up the old one and test all the cells etc, I will!


                Originally posted by mhs999 View Post
                Thanks for the advice. I ordered a new battery. Hopefully that does the trick. If at some point, I have the time/energy to open up the old one and test all the cells etc, I will!
                I think that a new battery will solve your problem.


                  Hi mhs999
                  Thks for your post, I do have the same problem and since I was looking for answer. So did a new battery solved your problem? If yes I will ordered one myself.