48V might be a good idea in your application, but realize this. You need to disengage the motors somehow above certain speeds. The issue is, if you gear those 48V motors for lets say 30mph tops, where 48V is 30mph, lets say that the motor rotates at 3000RPM, and you have a 15" radius tire. Lets say you put a 7:1 ratio from shaft to axle. That'd make you right around 30mph.
Now go twice that speed with the diesel engine, if you don't disengage the motor, you're spinning that motor at 6000RPM, which it is not made to do. It will fly apart. I've seen it happen.
Now, for your situation, you don't need a ton of power, but you're talking to EV-only guys. There aren't many (if any) Hybrids here, and many vehicles are built for MUCH more than 20kw. That wouldn't barely move a vehicle past 20 MPH for most of these vehicles. So you're situation is a little different. But for safety, low RPM, low power, 48V isn't so bad. Lots of off the shelf controllers, motors, chargers, batteries, BMS is easier (if used), DC-DC converters are easy to find, but the cable size goes up. Current capacity of the controller may need to go higher as a result.
One thing to remember is that RPM is volts, the less volts, the less RPM. Torque is amps. The more amps, the more torque. So to get more HP at low RPM, current goes way up, and the motor MUST be able to sustain high amps in order to pull the same power levels as a higher voltage lower RPM motor.
Now go twice that speed with the diesel engine, if you don't disengage the motor, you're spinning that motor at 6000RPM, which it is not made to do. It will fly apart. I've seen it happen.
Now, for your situation, you don't need a ton of power, but you're talking to EV-only guys. There aren't many (if any) Hybrids here, and many vehicles are built for MUCH more than 20kw. That wouldn't barely move a vehicle past 20 MPH for most of these vehicles. So you're situation is a little different. But for safety, low RPM, low power, 48V isn't so bad. Lots of off the shelf controllers, motors, chargers, batteries, BMS is easier (if used), DC-DC converters are easy to find, but the cable size goes up. Current capacity of the controller may need to go higher as a result.
One thing to remember is that RPM is volts, the less volts, the less RPM. Torque is amps. The more amps, the more torque. So to get more HP at low RPM, current goes way up, and the motor MUST be able to sustain high amps in order to pull the same power levels as a higher voltage lower RPM motor.
