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Conversion Help

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    Conversion Help

    Hi this my first post and i'm probably going to reveal myself as completely unclear on the concept, but i have to ask because money on the line.

    I have an old 24v bike i want to convert to lithium batteries. I ordered 30 samsung 2500mah cells from ebay because that's what i could afford. My intent being to build a 7s4p battery. So questions are,

    1.) Is this going to be woefully inadequate for a motor rated 400 watts?
    2.) If it will work to get me back and forth to the store and later i decide i want to double my capacity, can i simply build another pack and charge it in parallel or will i have to rebuild the pack?

    Sorry for jumping in with questions i might have answered by reading but i've got browser tabs open on ebay and amazon, trying to figure out how to allocate my money and if i can even afford to do this. Thanks for any advice.

    So i got this thing built with a 7S5P pack of Samsung 25R cells and it seems to be adequate. As well, i have a better understanding of how i will expand capacity. The only problem i'm having is that as i approach full throttle the power drops out. On level road i can go about 13mph and i'm pretty sure it went 18+ with the SLA batteries. I don't think it's a matter of overloading something because at 13mph on level surface i'm drawing about 120 watts but when it's struggling up a hill it's pulling about 310.

    My question is how does the throttle work on a brushless motor? It has three wires on it and the only example schematics i've been able to locate show a simple variable resistor with two wires. I don't want to cut the wires to test when i don't even know what i'm testing for.


    • tklop
      tklop commented
      Editing a comment
      I have no idea about your specific system...

      But I did have a thought...

      Perhaps your system--as previously configured--had it's "speed limits" adjusted (or switched off) via the display or controller...

      Now that you're on your new batteries, perhaps everything has reset--and you're experiencing a "default" speed-limit setting that's lower than you'd like (say--for example--the system default was for 20 or 25 kilometers per hour). That might result in your symptoms.

      If this is your problem, you might be able to locate good instructions on how to adjust the settings in your system (depending upon your system, YouTube may have handy configuration videos).

      Best of luck!


    It's a old Lashout
    Not much system to it, just a battery, a motor and controller, and a thumb throttle. I put a digital meter on it to monitor power is the only difference.

    I'm pretty sure the controller isn't stock either. But i don't remember speed governor in the features.

    Oh and, i went ahead and ordered a new thumb throttle b/c it was only $15 and seems to be a pretty standard thing. But that still leaves me wondering where three wires should go, i dont want to trust to color coding.
    Last edited by Joe McPlumber; 07-03-2019, 01:06 PM.


      There are two types of throttles. Potentiometer type which uses resistance. Which put out 0vdc to 5vdc. And hall sensor type that uses electronics. Which put out .8vdc to 4.2vdc. With the respective controller (or programming) for each type expecting those input values.

      A simple test for resistance type is a change in resistance when moving throttle, checking from one end terminal to middle wiper will tell you which one you have. As a hall sensored one won't change in resistance.

      Then it's a matter of checking it's voltage output when it has the correct 5vdc input voltage and ground. (see top line) To find correct wiring connections for hall sensor throttles, use this thread...

      Any questions let me know.

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


        Well it appears my throttle is a potentiometer type but it has two wipers, one from low resistance to high and the other vice-versa which is why it has 3 wires. So incidentally i bought the wrong sort of throttle because on Amazon it's just described as a "throttle for electric bike" and it has three wires.:/

        In any case while i was fiddling around i unplugged a circuit on controller and now my bike go fast. It's one white wire coming off the contrroller, plugged into its own self.

        Anyone have any idea what i did?


          It is not uncommon for a controller manufacturer to install a speed limiter circuit on their controller so that it can be sold in countries that have strict enforcement of speed/power limited laws. Yet that can be removed if not required. From your description, you just disabled this "derating" or as you mentioned, "speed governor" feature.
          See my completed Magic Pie V5 rear hub motor E-Bike build HERE.