Hmm, there really aren't too many BLDC controllers that are setup for 12V, except those for rc motors. So 24v makes sense simply because there are a ton of well priced controllers at that price.



The thing is that the controller fets are seeing phase amps, and for a given motor setup, a 24v controller could actually be more difficult to control. Because it's a BLDC motor the author needs to be careful about how the max speed compared to the typical usage speed.



Say 12v gets you to 10mph, and you don't want to go faster than that, and you typically go 5mph. If you run 24v on that, your top speed will be 20mph. If you want to go 10mph at 12v and pull 600 watts you will need 50 amps from the battery, and you will feed 10amps through the fets. If you want to go 10mph at 24 with 600 watts power you will need only 25 amps from the battery, but your duty cycle will be 50%, and the phase wires will still see 50 amps. The controller however will have more switching losses at 24v. I haven't given the best or 100% perfect answer here, but the general idea is that it's not necessarily better to run higher voltage.



Running a 1200 watt motor is a good idea, because the wheelbarrow application is not a very ideal situation for the motor. If the motor is capable of 1200watts, it will be more likely to survive the less than ideal conditions of running it at slow speeds.



It looks like he's running a "magicpie" it's by goldenmotor. They're decent hubmotors, like 9C continentals, but with a built in controller. I don't know if he's running it with or without the builtin controller. The believe the builtin does not put out 1200 watts, so maybe he's using an external one, which would actually be more reliable. You can run the magic pie at 3000 watts without burning it up, but if the conditions are bad, you can burn it up at 600 watts. Electric motors are different than gas motors in that they have a peak power at which point you have dramatically increased heat losses, but they also have a big range below that peak power in which if you treat them well you can coax a lot of power, but if you don't apply them properly, you can burn up the motor. That's why often a motor is derated, because if you run it at full power up a steep hill you'll burn up a motor that could otherwise deliver that power if you were on flats. But if you run at half power the same motor up the steep hill, it could possibly tolerate that hill before building too much heat.