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BBS02 won't start - is it the controller?

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    BBS02 won't start - is it the controller?

    I have a relatively new BBS02 36v 500w installation that now won't start. I think it might be the controller but don't know how to test/isolate and if it is I can't see how it has suddenly failed. Please can anyone help with ideas?

    One morning I checked the bike and the inline wattmeter was dead. I unplugged it and plugged it back in to a huge spark on the controller side. I tried again connecting the battery to the controller without the whatmeter and again a huge spark stopped me plugging in. I tried again and fried the XT60 connectors. I replaced the connectors, fried again.

    I have replaced the XT60s for XT90s. They plug in without a spark and the BBS02 seems to click/engage but the display won't turn on.

    The battery is charging to 41.7v and each cell is 41.7v. Tested with a multimeter.

    I tried bypassing the display using a programming cable but the throttle doesn't work. It appears that it's not the display.

    If the battery and the display are ok then it might be the wiring from the controller or the controller. But how to test and why have they died?

    Can anyone help?

    You’ll find more info here -

    Check some of the sticky threads for various troubleshooting tips for BBSXX units.

    Sparks while connecting power to controller wiring is normal but if destroying connectors in a short time, that isn’t normal.

    Display can be bypassed by either plugging in a program cable (not using the USB plug) or learn from kb (knowledge base) how to jumper the display connector to power the system and test battery, controller and motor functionality without the display/dash connected to the system.


      I've followed the knowledge base and I'm as sure the battery is working as I'm sure the display isn't the culprit.

      I've taken off the controller and found a little water/moisture inside. The controller and wiring are silicon sealed but could this be the problem? How do I test if the controller is blown?


        I couldn't find any posts, FAQs, guidance on how to test if a controller is blown so after checking everything and replacing XT90 connectors once more I tried again. I plugged the battery and controller together nothing happened. So I bypassed my display again using a programming cable but when I plugged together my XT90 connectors they didn't just spark they glowed. I could only conclude the controller was causing a problem. I removed the grey potting from the controller and eventually found what I think is a burnt out circuit board. See photo. If

        There was water in motor housing when I opened the controller so I conclude that moisture found its way down to the controller board.

        This all figures now. I washed the bike down after a ride and left the bike with everything fine. But 24hrs later the watt meter had died. It worked when I only plugged in the supply side battery. I just didn't think water could have got into the controller.


          Now I'm paranoid. I rode a very dusty trail and was ready to hose the bike down. Maybe a damp cloth or compressed air would be better.
          Was the motor hot when you washed it?


            Originally posted by max_volt View Post
            Now I'm paranoid. I rode a very dusty trail and was ready to hose the bike down. Maybe a damp cloth or compressed air would be better.
            Was the motor hot when you washed it?
            I hosed off my ebike once after a muddy ride. I let it dry for two days in the cold garage. When I turned it on, it blew the controller. It turns out that two days was not enough allow for a bit of water in the vicinity of the controller to completely dry out. The controller was beyond repair.

            Now I never hose anywhere near the electrical components. I carefully wipe down those areas with a moist paper towel.


              Older BBS02's have 2qty so called "drain holes" where the bolts secure the controller to motor. I wouldn't go wading, use a hose or allow much front wheel spray to hit one of those units. Don't ask how I found this out...

              I can't say anything about the newer version BBS02.

              However, my BBSHD's have no problem rinsing them off with a hose. No pressure spray but I do rinse them off and haven't suffered any water issues.


                I don't know if I'm unlucky but it seems the BBSXX motors are waterproof but not 100%. Like a couple of folks above this has made me paranoid when I was doing all I could to waterproof the install so that I didn't have to worry. On the plus side I've learnt lots more about the BBSXX, my battery and wiring. My bike's controller burnt out while the bike was left with the battery in situ. The BBSXX does have an on/off switch operated from the handlebar switch via the display but like a TV on standby, the controller's circuits must remain live. The design of my battery and install is in a very tight spot within a full suspension bike's triangle so I can't have an off the shelf clip in and out battery pack. The battery is housed in a custom built aluminium case and not so easily removed or unplugged day to day. I've ordered a remote solid state on/off switch from lunacycle so I can isolate the battery from the controller while it is parked up.


                • commuter ebikes
                  commuter ebikes commented
                  Editing a comment
                  "in situ". I had to look that up: "in its original place". Thanks for teaching me something new.

                Update - New controller installed and all working perfectly. There isn't even a hint of sparking if I test connecting the Xt90 connectors whilst the battery is life, but now I have the added security of a solid state on/off switch between the battery and controller. Bought from Lunacycle with an extension for the on/off switch and Xt90 connectors.

                I wonder (but can not say for certain) if people who have problems with sparking actually have a moisture issue rather than accepting that it's just the way connecting batteries to controllers behave sometimes. Talk of this had me chasing shadows for a good while.

                I've also bought a second Bafang kit so in the future I can swap out components to diagnose issues.


                • calfee20
                  calfee20 commented
                  Editing a comment
                  Ok I'll buy that, for the main power connection but it should be ok for every where else.

                • ykick
                  ykick commented
                  Editing a comment
                  Yes most definitely for everything else. Just not main battery to controller connectors.

                • Frits-Fietsema-95
                  Frits-Fietsema-95 commented
                  Editing a comment
                  I've put dielectric grease into the entry hole of the wires into the controller of my BBSHD to prevent moisture getting into the controller. Is dielectric grease somehow screwing everything up inside the controller or is just heavy rainfall enough to destroy the controller? And how often do you have to spray the connectors with clean dry spray?

                I bought a BBS02B and a Dillinger 48V battery. From different suppliers because I'm a N00B. Assembled the ebike, which went well. The first time I started it the display came on but no power to the crank. I then received a replacement controller from the first supplier (reconditioned by the look of it) which was a lot better. I rode it around for about 15km, and thought "great!". I rode it the next day as well, all good. I then went on a business trip for a week and when I came back I got as far as the end of the street. (about 100m), indicator showed 0% battery. Switching to Volt it still shows 52V or so. Battery indicator on the pack also shows it's as full as a fat lady's shoe. I've checked all the connectors as per the instructions on this forum. I've long charged the battery for 24 hours. I've already ordered another controller for it for $90 clams from Dillinger this time. But just to make sure I'm not completely stupid and wasted my parent's money on a degree in electrical and computer science. Is it the controller or the battery?


                  Hi, my bike did die today also. I´ve had it for more then 8 months. And suddenly nothing happends when I pressed the button. I have also checked battery with multimeter, giving me 41-42V. I did try to solder this one. The plastic had a crack in it and some stiffs where bended. But it seems to be working now. Don´t now it this small thing can make a different. I did try to clean the pins and also where its connectecd in the battery. I did try to connect it after this and the screen turned on!! But only for 30s, when I tried the throttle it died again.

                  I´m really not good at all in electrics, and I really really need my bike to get to work, and to bring my dog home :( So please! Can anyone give me more tips? Can I open the controller unit when it´s mounted on the bike?