This is awesome! I’m going to throw this formula into an excel page and noodle around with it to see what motor/battery combo I need for myit's my impression that you can in principle feed them any voltage. it's not like a 24V motor will melt if you feed it 36V. volt in principle can't hurt it BUT volt motivates current to appear. the higher voltage the more current will tend to appear and current can destroy a motor. to really understand it you have to understand the physics concept of work. nature has a magical way of ensuring you pay for the work a motor does. work is the force (or torque) applied over a distance. if you apply force and nothing moves you don't have to pay for it. just like a paper weight is free force. that force (or torque in the case of a motor which is just force going in circles) comes from the current and the work done during rotation is paid for with voltage. you can imagine a worker that only does as you pay him.
this means for instance if the motor is stalled, let's say up against a wall and can't turn even a little voltage will make the current rise a lot because there is no rotation and no work done. you pay voltage and it tries to make work. when it can't the current rises dramatically, in theory infinitely if it weren't for resistance in the wires. but going 100km/h it wants a lot of voltage to maintain a current level. if you don't feed it the current will drop to the level you feed it. nature has a 'magical' way to make sure you get exactly what you pay for.
so voltage motivates current in a balance with how much work the motor does. slow rpm it's easy to motivate current to appear. high rpm it takes more voltage.
a motor's limit is a current limit and not a voltage limit BUT there is an indirect voltage limit because the motor can only handle so high an rpm for mechanical reasons.
let's say a motor is rated at 150A continuous and 5000rpm and that at that speed it takes say 100V to keep the current level at 150A. so you might say that 100V is the max for that motor BUT a motor can take more current briefly so let's say you want it to peak up to 450A then you need 300V to keep that level at 5000rpm. that would be 450Ax300V=135kW (or around 150HP after efficiency)
the power formula you can use is
P = T x w = T x Hz x 2 x Pi where T is torque, w is rotational speed in radians per second, Hz is revolutions per second, Pi is 3.1415...
torque is a direct result of current in the motor and that relationship you can look up in a spec sheet for the motor. a current torque graph (not always available) here are some example curves: http://www.zev.dk/misc/torque-curves.gif
once you have that for your motor you can use the above formula to roughly figure out how much voltage your desired performance will take at the motor's max rpm. it gives you a power value for your chosen current which you can then get voltage from using
P = I x V
where I is current and V is voltage. P is power.
IIRC
‘65 beetle to go 70-80mph briefly but be able to cruise at 60 or less for a 100 mile range
