Now for something that many people might be interested in for creating a radio controlled Power Wheels: wiring up a speed controller that can controlled by the throttle channel of a radio system.
I'm using a Traxxas VXL-3s ESC because it's just an extra I have sitting around. It can handle up to a 3-cell lithium polymer battery (11.1v) and is rated for 200A continuous and 320A "burst". I think it should be able to handle the current draw involved in a Power Wheels. It also has a "training" mode that cuts speed and power in half. There's plenty of other ESCs out there that could work even better because they can handle more voltage and amperage and are more configurable (torque limiting to keep the gear boxes safe, for example). When my kid is ready for more speed, I plan on trying the Mamba Max Pro ESC by Castle Creations with 6-cell lipos (22.2v).
You're probably thinking, "11.1v? That's gonna be slower than the original setup with the 12v battery!". Lithium polymer batteries (lipos) can supply tons of amperage and don't drop in voltage much under load. I haven't measured the speed with a GPS yet, but I'm pretty sure that my 2-cell lipo (7.4v) is nearly the same speed as running the original 12v battery.
. I have some actual measurements now, and it's slower than I thought, but still faster per volt than the stock battery. See here
Other benefits are that they are much smaller, lighter weight and can be charged faster. The original battery has a capacity of 9.5Ah and weighs 10.5lbs. Two 5Ah
5.3Ah 3-cell lipos (11.1v) wired in parallel would give you 10Ah
10.6Ah capacity, would weigh about 3lbs
1.8lbs (more details here
) and would fully charge in about 1.5 hours on a decent lipo charger (could charge faster if you have a charger and power supply that can charge at higher amps; as quick as 15 minutes if you have some real serious equipment).
Anyway... on to the mods. The motors need to be wired up so they can be connected to the ESC. Bullet connectors are typically used. Some ESCs have female bullet connectors pre-installed, some don't. Just make sure you know exactly what kind of connectors you need. In my case, it was 4mm bullets. So you'll need wire (I suggest 12g wire from a hobby shop, made for high-powered RC cars), connectors, shrink tubing and soldering tools/supplies.
Also pictured above are 2 "Y" harnesses I made with one male connector and 2 female connectors each. These will be used to connect the two motors to the ESC in parallel.
Figure out how long you need your wires so that they're reach the ESC. Shorter wires are generally better, so try to find a place near the motors for the ESC to call home. Solder wires to the motor's tabs, and add male connectors to the wires. Notice that the red and black wires are connected to opposite tabs on the two motors. This is because the motors need to spin in opposite directions.
Now I'm not actually making an R/C Power Wheels, but you probably want to, so I'll show you how everything gets hooked up with a radio system.
Motors plug into the ESC (that's the blue thing with black cooling fins). This ESC can run brushless motors, so it has a third wire that will not be used with these motors. Make sure you understand how to hook up the motors to your ESC and configure the ESC to run the motors properly (RTFM). If you get everything setup and find that the vehicle goes the wrong direction, you can swap the wires, or your ESC might even have a "reverse motor direction" setting.
The battery (that's the shiny blue rectangle; it's a 5Ah 7.4v lipo battery) plugs into the ESC. Make sure you know how to setup the ESC. A special mode is necessary for lipo batteries (RTFM).
The ESC plugs into the receiver (that's the tiny circuit board; the plastic case was removed so it would fit better in the RC car that I borrowed it from) on the throttle channel (channel 2). The ESC supplies power to the receiver, so no additional batteries are necessary. Make sure you know how to calibrate the ESC to your radio system's throttle signal (RTFM).
There you have it... fully proportional and radio-controlled throttle, braking and reverse. None of the original wiring or switches are necessary. It's modular so that you can easily swap out the various components for upgrades. All that's left to do for a fully radio-controlled Power Wheels is to rig up a steering servo and plug it into the receiver. For my project, I'll be making my modified throttle grip and pedal generate the same signal that the receiver would provide to the ESC. I'm thinking about making it support some kind of radio-controlled override so that I could take over the throttle while my kid is driving it :)
NOTE: The ESC, receiver and battery are not secured in my picture. ESCs and receivers can usually be simply mounted with double-sided servo tape from your local hobby shop. I still need to work out a way to restrain the battery. It will probably involve some foam padding and a velcro strap.
And just for good measure, here's the video of the radio-controlled throttle in action again: