Variable speed from a 24 volt battery bank

G'day Guy's,
With my cnc I'm using a deep cycle 24 volt bank as the primary power supply and for the spindle which is a 300 watt motor I was thinking just say a 5K pot would do the trick for varying the voltage to the motor. Now would this be right or am I on the wrong path.

If you mean putting the 5K pot in series with the motor it wil not work. A 300 watt motor at full load on 24 volts will take 300/24 amps = 12.5 amps. (These figures are based on 100% efficiency. It will probably only be about 80% efficient.) The current through a 5K pot with 24 volts across it will only be 24/5000 amps = 0.0048 amps. What you would need to do is build a PWM (Pulse width modulator.) speed controller. You could use the 5K pot to control the duty cucle of the PWM controller.

Les.

Pull the speed controller out of an old 18+ volt cordless drill and modify that to use a potentiometer rather than the sliding trigger.

This can handle 30 amps:
**broken link removed**

Bryan! Good to see you, mate! It's been a while!