I recently bought a 36V BLDC motor controller (the $10 ones from ebay) without taking into consideration that when fully charged my battery voltage is actually 42V.
I found a similar question where they suggest adding a voltage regulator/converter which seems like a viable solution, however at my power rating (500W) there will be a considerable amount of losses.
By inspecting the board it's visible that there is no lower voltage input and there is actually a 5V output for a potentiometer which means that there is probably a buck converter on there. In standalone buck converters the output voltage does not change if input voltage changes as long as it's in some range.
So the question is will I fry the board if I connect 42V to it and if yes is there anything I can do besides buying a higher voltage board?