I have two motors from the back wheels of an old Rollin' Rambler kids powered car (https://www.amazon.com/12V-Rollin-Rambler-Ride-On/dp/B00S713PW4). Unfortunately, I didn't get the wiring harness and controls out before it was thrown away. I'm thinking of using one of the motors to make a vibrating parts cleaner, but want a way to power it without having to use the battery. The car had a slow and fast speed, so I'm assuming it supplied maybe 6 or 8 volts to the motors for slow speed and 12 volts for fast speed. However, I don't really know how many amps the motor pulls. I can't find an exact one online using the numbers on the motor housing, but I think this one is similar: https://www.amazon.ca/SODIAL-15000-Electric-Motor-Spare/dp/B078CR3P86
That description has 35-45 W. If I understand it correctly, that equates to 2.9-3.75 A.
I also have an old laptop charger that outputs 19.5 V and is rated for 3.33 A. I'm wondering if there's any reasonable way I could use this charger and a resistor or something to power this motor at 12 V (or even less volts if that will reduce the current to an acceptable level for the charger).
From what I can figure, to use this charger to power the motor at 12 V and 3.75 A (I know it might even pull more amps on startup), I would need a 2 Ohm resistor:
- (19.5-12)/3.75 = 2
But then I think that would require the resistor to be rated for almost 30 W:
- (19.5-12)*3.75 = 28.125
So, is there a reasonable way to power the motor using the charger, and are my calculations correct?