Brushed ESC Overvoltage Failures

Written 2017-10-26

Tags:Motors ESC 

A brushed DC motor ESC(Electronic Speed Controller) is a relatively simple device with only a few things to do, so it is interesting to consider what might happen when one is taken outside of its designed operating parameters. Today I needed some cheap ESCs to run on higher voltage than designed, and one of them did not quite make it.

An ESC has at most a few subsystems:

They usually only fail from overvoltage in a few different ways:

Today we connected two ESC to first 12V, then 24V, and attempted to drive a 1980s industrial robot. The first ESC, a 10A Hobbypower Rc ESCa, is designed for up to 8.4V and uses an IRFS3006 H-bridge. At 12 volts, the little controller was able to smoothly accelerate our robot, though it was a bit slow. BEC output remained steady at 6V. The second ESC, a 60A Hobbywing Quicrun, is designed for 12V systems and performed admirably with little lag or ramp-up, however due to the larger current drivers it could brown out our test supply if the robot were commanded to move too quickly.

At 24V the plot thickens. The Quicrun ESC functions just fine. However the Hobbypower ESC failed catastrophically at 24V, destroying the ESC, receiver, and an innocent servomotor. Postmortem indicates that the BEC failed, shorting the 24 volt battery voltage into the BEC output. Once the BEC output rose above 6V, the failure cascaded to the reciever, which connects to more servos, destroying them as well.