Can I increase the voltage of my 24V Heinzmann hub motor?
It's a 400Watt, Imax=30Amp, Inominal=21 Amp
Can I go to 36V? Can the controller handle it?
Yes, But... Most likely you would need a new controller. If it's an EVG, that means losing most of the bells and whistles, and having a simple throttle, and having to install new switches to run horn and headlight. The tailight is 24v only.
You also need to be sure to keep the temp switch from the motor functional. The motor will get hot faster. If you do like I did, and use a 35 amp controller instead of the stock 20, your motor might fry in 30 minuites like mine did. Others, that listened to the advice to use the temperature switch to shut off the new controller, and use lower amp controllers have had good results. Top speed will be better, closer to 20 mph instead of 12. Generic brushed controllers are cheap enough to give it a try.
Sounds like you have a different gear ratio in your motor than I had, from EVGlobal bikes. On the EVG bikes, the motors were designed for a controller in the 20 amp power area. My use of the 35 amp Wilderness Energy was toleable at 24v but at 36, it smoked the motor. The main thing to remember is the motor is designed for a certain wattage, so increasing that means keeping and eye on temperature is pretty mecessary.Lots of brushed controllers on ebay, or from scooter parts houses on the web. Ecryazyman is the best ebayer.
The thermal switch can be wired into the circuit for the on off switch, so look for a controller that has one, or it can also be put into the circuit for ebrakes if the controller has no on off switch. polarity doesn't matter to the sensor in the motor. To test the sensor, see if it allows current to pass through it when cold, a bad sensor in the motor will not allow current to flow at any time.
I agree with everything Dogman mentioned. Please wire the thermal switch if you are overvolting you motor.
Can you please share how you converted the pedal 1st of immediate start. I have the same setup on my wife's
folding ebike and would like to get rid of pedal 1st feature.
I don't have one to trade at the moment, but I can recommend a good source. PM me for details.