I have 2 identical DC motors rated at 12 volts each. I also have a 12-volt power supply. If I put these in parallel, would the motors draw their required current, or is it limited to the current drawn from one motor? I.e. if both motors draw 0.1 amps each, will there be a total of 0.2 amps drawn from the power supply if the motors are in parallel, or will the total current be limited to 0.1 amps because 'amps are shared in a parallel circuit'? Or, perhaps, would it be best to power the 2 motors in series with a 24-volt power supply?

The power supply will easily be able to handle the currents that the motors draw - it is only a small scale application.

I don't feel like much context is needed for this question, but please ask if necessary.

Many thanks in advance!


A parallel configuration is best, because then the current of one does not affect the other motor. The current will be doubled so you'll need a power supply that can handle twice the current than that of one motor. If one motor draws 0.1A then two in parallel will draw 0.2A

Or, perhaps, would it be best to power the 2 motors in series with a 24-volt power supply?

Not a good idea.

  • \$\begingroup\$ Thanks for this. I think I confused myself as I have had this configuration before, but with batteries instead of a power supply. When another motor was introduced to the circuit in parallel to the other motor, the motors operated at a lower RPM. I assume this is because the extra current drawn from the secondary motor creates more internal resistance for the batteries, thus reducing the voltage supplied to each motor? \$\endgroup\$ – Callum Sep 20 '19 at 18:16
  • \$\begingroup\$ This happens if the supply has internal resistance, batteries can have a higher internal resistance in the ohms range than a power supply connected to the wall, so it would cause a voltage drop when more current is added to the batteries (the supply). The battery voltage also drops when more current is added. Another problem is if you have a long cable this could also cause more resistance and voltage drop. \$\endgroup\$ – Voltage Spike Sep 20 '19 at 18:20
  • \$\begingroup\$ @Callum, it doesn't necessarily create more internal resistance, but the internal resistance will drop more voltage when you connect the battery to a higher current load, so the battery output voltage will be lower when you add more motors. \$\endgroup\$ – The Photon Sep 20 '19 at 18:20

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