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Thumb throttle question / bike inoperable

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    Thumb throttle question / bike inoperable

    Hello all, i have been lurking for a few days and decided to join as i need help on a project i took on for a good cause, long story short i do a lot of DC projects as a hobby and do automotive electrical diagnostics as my day job, i have modified powerwheels and golf carts but this is my first run at an e bike. Essentially i responded to an add for a man in my town asking for anyone with experience with Lithium cells, he asked if i could verify his two 48v batterys, easy enough. Opened up both cell packs, one needs a new BCM and the other is flawless, then he asked if i could take a look at the bike itself and figure out why it is not working, and because i am a glutton for punishment i responded with dont threaten me with a good time.

    The kit is a generic china 1000w 48v front wheel with a thumb throttle (push button start with analog led power meter) as i have read over the past few days this in and of itself can be an issue, but i digress.

    i have checked voltages at the connectors as outlined in the almost comical instructions and it they are within range, but still nothing at the motor, the part i do not understand is when the switch is toggled the power guage lights up to full power and then after a second or two drops to half, then low, and then off.

    Also noticed that when the above is happening, if i probe the wires off the battery the voltage drops from 50v down to 9v and then back up to 50v when the throttle shuts off, this may be a fluke but worth mentioning.

    I have opened the controller and looked for any obvious signs of damage, bad soldier, or blown mosfets and verified all capacitors are good and performed basic continuity tests, however the support on this controller for a schematic is lacking.

    Checked all connectors and verified all pins are in the the correct spots (based on wire color)and made sure no pins were loose or dragging.

    opened up the throttle and noticed the white signal wire looked a little burnt and the soldering was un shielded whereas the power and ground are shrink tubed, in an attempt to free the sensor the power wire snapped off the base of the sensor so im replacing the throttle anyways to fix my mistake, but after that i am stumped, i am not one to throw parts at things, and cheap as a new throttle and controller are i would like to know what the issue is for my own sanity.

    Sorry for the long winded question but i was up until 2am racking my brain and i would really like to help this guy, as i mentioned it is for a good cause as he is building this for his disabled son and has been trying himself for a few weeks to get it going

    Perhaps apply some DC Voltage (12V?) to test the controller and motor?
    A ' Throttle ' is inexpensive but not available at the local super market.
    Then continue troubleshooting.
    Last edited by Mike_V; 05-08-2020, 10:34 AM. Reason: V test?


      Thanks for the advice, im going to try that shortly, i have since ordered a new throttle and controller and should be receiving them wednesday, i figure either ill need them or if not im omw to my own project when this is over


        Good luck, I'm just a test guy.