So yesterday, I took my scooter out for a ride around my neighborhood, giving it a decent amount of throttle for about 30 minutes.
On my way back, the throttle response started sputtering at higher throttles, at first I thought the parallel connections of my battery had broken (again), but this was not the case.
After checking a few others things, I noticed that the heatsink of my Tampa VESC 6+ and my 63100 motor from Saite were both too hot to touch, so I ultimately ruled the sputtering throttle response as due to thermal throttling on the VESC.
It is not thermal throttling on the motor because I have that disabled on my VESC, and I did not have this issue with a Flipsky 6.6 running the exact same settings (maybe I screwed up and the VESC is throttling off the motor temperatures).
I took my scooter out for a ride later after everything cool down and the sputtering was gone.
So an interesting thing is, when I ran my scooter with a Flipsky 6.6 ESC, I never had this problem.
I run a 10S battery, average voltage was 38-39. Motor amps 80A, battery amps 40A, the sputtering happened under heavy throttle. Some back of the hand calculations with the DirectFETs show that switching losses and conduction losses are about equal at 40A, with conduction losses dominating above 40A motor current. It’s 4W per phase leg, or 12W in total. The thermal resistance of the heatsink is around 10C°/W based off the surface area and the thermal conductivity of aluminum. It sits on top of a piece of polyurethane foam.
I was wondering if anyone else has encountered this phenomenon, and if not, if someone could show me what I am doing wrong.
The Flipsky 6.6 uses MOSFETs with a better figure of merit (Rdson * gate switching charge), so they dissipate around 60% of the heat in similar operating conditions, if my estimates are correct, and would likely explain why I never encountered this issue previously with the Flipsky ESC.
Or maybe I screwed up the motor temperature settings.
Or I just need to not put this thing on top of a THERMALLY INSULATING piece of foam.