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Bike powers off, then on again.

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    Bike powers off, then on again.

    Hey Everyone,

    I own a Fat tire Sondors X , but have been buying parts/accessories/LCD from Luna as required.

    However, in the past couple of weeks. the power will spontaneously shut off (50-90% charge still left in the battery), and then it will spontaneously restart 10-15 min later.
    i HAVE read similar threads on this forum, relating to wiring to the battery connectors, bad soldering, etc.

    But , i have noticed a couple of things, from observations, that might be different from other threads.
    A - when it does shut down. if i open up the bike/battery frame case and check the battery life of the battery. it reads Dark/dead (no lights).
    B - when it does power up gain. checking the battery will show the 2 or 3 lights of power illuminating.

    i was originally thinking this was a controller issue, or loose wiring issue. but it looks to be a battery issue due to A and B.

    the same 'A' and 'B' applied, when i physically removed the battery from the bike to charge inside and check the fuse.
    it showed "Dark", no power. I checked the fuse, put it back in, and the power returned.

    with luck, it IS a fuse issue. i recently bought 30A replacements from a Hardware store. but i will be out of town without trying the bike for a couple of days.

    any thoughts are appreciated.

    Fast answer, albeit not a very good one, below!

    A thermal fuse which resets is sometimes included in devices. It would shut down with high current and heat, perhaps. Then reset when it cools below the set temp.

    I do NOT know if there is one on a Sondors pack or ebike. But the symptoms would perhaps fit, if so. Maybe search accordingly, possible wild goose chase.
    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


      HI JPlabs.

      i would agree with your reply back to me (thanks by the way), but it wouldn’t be the case here.

      I went to go to work with it in the morning (cold). Zero power at the pedal, showing dead battery on the battery gauge. Took my other bike to work.

      I came back home to play with it, and poof, power works immediately and battery shows 80% charge.

      i think it could be a demon bike, or it’s just f**king with me...


        If the replacement fuse didn't sounds like an internal intermittent battery wiring problem... :-(

        That said, some BMS's provide low temperature cut-out protection! But surely at this time of year, it must be warmer than this...even in Canada? ;-)

        " A BMS may protect its battery by preventing it from operating outside its , such as:
        • Over-current (may be different in charging and discharging modes)
        • Over-voltage (during charging)
        • Under-voltage (during discharging), especially important for lead–acid and Li-ion cells
        • Over-temperature
        • Under-temperature
        • Over-pressure (NiMH batteries)
        • Ground fault or leakage current detection (system monitoring that the high voltage battery is electrically disconnected from any conductive object touchable to use like vehicle body) "

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


          Yes, it does sound like something inside the battery to me, as well. Maybe try a jump start of BMS next time it shows nothing.

          Pulling fuse worked once, right? Does that always work? Also, moving fuse might change something. Jiggle that, make sure both sides of the holder grab tightly, etc.

          Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


            I had the very similiar issue on my bike.

            I ended up bending the pins just a little bit where the battery slides in.

            Never had a problem since, it seems to me it just doesnt connect well enough. I also have brought some velocro straps and wrap them around to stop all battery rattle.

            Never had a problem since.

            Hope this helps.



              I have the same issue. The display would on for a second and then completely blank. Similar to this -

              My set-up is BBS02, battery 48V. I have a video of my circus - It may be observed

              1. the voltage of the wire coming from battery is about 53V.
              2. if i connect one of the battery wire (either the positive or negative) to the wire from BBS02 the voltage remains same.
              3. if i connect both wires of the battery (positive and negative) to the wires from BBS02 the voltage drops.

              Before doing test (the video) i have changed the BMS (suspecting this as culprit) but the problem still continues. Any guidance would be very helpful.


                Does the problem re-occur with the main harness disconnected from the motor harness?
                See my completed Magic Pie V5 rear hub motor E-Bike build HERE.