*Use at your own risk, if you are not familiar with wiring up electronics seek professional advice before attempting install*
Upgraded my son's MX 125 to 24 Volts with a 150 Watt motor, like most DIY projects it was more involved than I planned for, but not to difficult.
Parts List:
MX350 24V Motor Controllers: https://www.amazon.com/dp/B01N0YXZBJ?...
150W 24V Motor: https://www.amazon.com/dp/B0831S8SR7?...
Charging Port: https://www.amazon.com/dp/B08LN7Q1LN?...
Chain with Master Link: https://www.amazon.com/dp/B089KFB83N?...
12V 5A Battery: https://www.amazon.com/dp/B079ZCJYP3?...\
30A Inline fuse holders: https://www.amazon.com/gp/product/B01...
Optional
Heat Shrink Connectors (for battery): https://www.amazon.com/gp/product/B07...
Heat Shrink Connectors (for splicing): https://www.amazon.com/gp/product/B07...