# Recommended current for 12V stepper motor

Hi
I have one of these stepper motors.

And I was wondering what the max current it could draw would be? I’m looking for a 12V battery to supply power to two of these, but I’m not sure what current it should be able to supply. If I knew the maximum absolute max current these could draw, sometimes called the “stall” current I think, then I would know what the battery would need to be able to provide.
Or even just what kind of current was supplied when it was being tested with the 9V and 12V that is described in its store page.
Or possibly even the resistance of the motor, though that would be more difficult.
Anyway if there’s anything I should know, or that you can clarify please let me know, I assume most of the 12V batteries for this kind of use would be suitable, but I’d prefer to be certain before purchasing one.
Thanks

Hi Bowen,

Unfortunately, it doesn’t look like Adafruit has provided that information for this product. Rest assured that it won’t be an enormous amount of current, however, the best option would be to set it up with a 9V power supply and measure the current draw using a multimeter under different conditions.

Hi Bowen,

Perhaps the easiest way to determine the max current of a motor is to measure the resistance of a coil with a multimeter then follow up with some maths (Ohms law):

V = IR

therefore:

I = V/R

(I = amps). You know that this motor is rated for 12VDC, so you can swap V for 12. Go ahead and swap R for the resistance of a motor winding. With the above formula, you have landed yourself the max current draw of a motor winding and you can then workout the other. Bear in mind a stepper motor typically has 2 active coils at all times, so multiply your result by 2.

If for example the resistance of a single coil was 10 ohms. 12 / 10 = 1.2 amps. Given two coils are powered at all times (typically), 1.2 x 2 = 2.4 amps.

It’s worth noting that this isn’t always the case. Some motors expect current control to be done externally and they will actually burn out if not managed properly. These and most hobbyist DC motors are fine to use the above method though - they will draw max current on stall, and everywhere in between the internal inductance will increase the resistance (reducing the current draw).

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Thanks for replying, I’ll try that