FA3: How to break-in electrical motors

The motor break-in process is very important. Not only does it increase motor life, it also significantly increases motor performance. For a brushed DC motor, the break-in process transforms the brushes, bushing or bearings and other moving/sliding parts from their new, out of the factory state to their normal operating state. Ideally, the break-in process for this type of electric motor starts by applying a voltage above the no load stall voltage, then slowly increasing the motor speed with intervals of voltage bursts. This process would require a motor driver, which is quite inconvenient. Since a flywheel system requires two motors, an easy way to break-in the motors is by connecting them in series to the battery (as oppose to parallel, which is normally how they are connected for maximum power). This will run the motors at approximately half of their final running speeds, assuming the same battery is used that will power the finished system. If the motors are slightly, or even significantly out of balance with respect to each other, it should not be a problem since all this will do is make one motor run somewhat faster than the other during the break-in process. As long as the motors do not have load on them and are below the advertised maximum operating voltage, it should not be a concern. One thing to note is to remove the decoupling capacitors on the motors (most aftermarket motors such as all Tamiya Mini series motors and RM2s do not have them, the PNs do) before performing this process, as the capacitors will randomly change the impedance of the motors from the brushes noise and make the load on the motors unbalanced. The schematic for the electrical connection of this break-in process is shown below.

Fig. FA3.1 – serial motors break-in process schematic

One thing to double check is the orientation of the battery connections to ensure that the flywheels spin the right way. A picture of the actual system is shown below.

Fig. FA3.2 – actual break-in process picture

Note that the motors are already placed in the flywheel cage. This is convenient because the motors do not have to be secured, but the flywheel cage does (tape it down to a surface with electrical tape). Also note that the positive connection has not been applied to the motors yet in the picture to avoid running the motors while taking the picture. Lastly, just because connecting the motors in series works for this process does not mean it can be used for the final build as a way of halving the voltage across the motors. Ideally, this will work in the perfect world. But in this world with its infinite random variables, a set voltage must be applied across the motors by connecting them in parallel with the battery.