Inside the Quark 125, pics.

[BrianG]

Thanks. Although without CartWheels taking it apart, we might have never known.

At first glance, 30v looks fine, if a bit close to a 6s charge. We might also have to think about the inductive kickback (back EMF) since the signals the ESC sends to the motor are square wave AC. Back EMF under a collasping magnetic field can be extremely high depending on the inductance of the motor coils. Of course, the reverse diode in each FET is supposed to help curtail this, but if it has similar limitations, it might no be doing its job. Maybe this also explains why some people can run 6s and some can't - the type and wind of the motor. Or it could be some FET batches have a higher tolerance than others.

The periodic problems with the quark simply can't be related to the current capability. Even grossly underrating the current of each FET for temperature, it still has plenty of current capacility. If each FET only supplied 10A, that would be three phases of 120A each (assuming 12 are paralleled per phase)!

Even with this "problem" the Quark is still a VERY nice ESC and wouldn't hesitate to buy it again. The construction as seen here is very high quality. They even added a heat spreader between the PCB instead of relying on pure stacking. So, we know we should only run 5s tops and add cooling for best results.