12V 500W DC Motor Speed Controller - Electric Brushed Motor Controller for E-Bike, Scooter, DIY Robotics & Power Tools - Perfect for Speed Regulation in Electric Vehicles and DIY Projects

I've been using this style of aftermarket brushed motor controller to 'upgrade' various Razor brand electric vehicles, mostly because from the factory they have a simple on-off throttle and this allows for the installation of a variable speed twist/thumb/foot throttle. It provides you a much smoother and less jerky experience and also the ability to maintain a lower speed for cruising. The other benefit to swapping the existing controller out is having a set of wires that passes the battery's voltage through it when the controller is turned on so I've been using that for the headlight and/or taillight power without having to add a relay or switch. For this controller in particular, I had obtained an old Razor MX350 kids electric dirt bike. They are sized and spec'd for a young teenager up to 140 pounds. The problem is that my daughter is only 6 years old and 60 pounds. The system originally ran on 24V with two 12V SLA (Lead-Acid) batteries wired in series. I first tried an aftermarket 24V controller so that as previously mentioned she would have a variable speed throttle and even limited the top speed with a 10k trim pot (resistor) in line of the +5V going into the throttle but it still just had too much torque in the low end for our comfort level. I got back online and found this 12V controller, pulled the batteries out and re-soldered them in a parallel configuration but with an XT60 connector on each battery so that I can more easily change things back in time when our daughter gains some more weight and experience. First pic is the unit out of the box and the second one is after soldering all new connectors on to suit my needs. This unit has been working great for about a week now and I noticed no difference in runtime. Even though the voltage dropped, the watt hours are the same at 168 in either configuration. I will gladly purchase this again if I ever need another 12V controller.