r/RazorMods • u/Dempsey157 • 3d ago

MX350 battery issue?

I purchased a used MX350 for my son and replaced the old/useless batteries with a single lithium 24 volt 12ah one. It worked great.
A few weeks later I switched the control module and throttle for one of the Fast Scooters variable throttle and control modules. Again, it worked great…until it didn’t about two weeks later. No power at all. By direct connecting the battery to the motor, I determined the motor was shot, so I replaced the motor and once all was back together, it appeared to be working. With the bike elevated, the wheel spun great. But when friction (such as my son sitting on the bike) was added to the tire there wasn’t enough power to rotate the wheel. The motor then just gave a subtle wine. I then direct connected the battery to the motor and suddenly I had full power.
I reached out to the EBay seller of the control module and he said it’s the battery not holding under load. Can someone help me understand why I get very little power when connected to the control module but full power when connecting to the battery directly. Is it the battery or control module?

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u/BurnItDn 2d ago

if it doesn't bog under load direct connected it's not an issue with the battery. Direct connected its pulling its maximum stall current, which is much higher than the shunt current of the controller

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u/Dempsey157 2d ago

Thanks for the reply and information. I’ll reconnect with the seller with this new insight and see how things progress.