I'm working on a project where I need a high torque stepper motor. The stepper motor being used is rated at 12 - 24 volts and when I used a 12 volt battery supply composed of 8 AA batteries it appeared to work fine.

Because I wanted higher torque I set the pot on the Easy Driver to 0.5 amps which is within what was recommended for the motor, and used a Lithium Ion battery originally being used for a power drill rated at 18V and 1.5Ah.

When I connected the battery to the easy driver the motor got very hot and would shake when I tried to turn it but not turn. Now the motor will not work with the 8 AA batteries either. Heres a link to the motor US Ship OSM 5:1 Planetary Gearbox Nema 8 Stepper Motor Samll Size High Torque.


What did I do wrong and how can I fix it?

P.S. I am using a photon as the micro controller and the motor is being controlled using the Blynk app I eliminated the chance of it having to do with the photon or Blynk App.

I found out that the battery I'm using is the Makita BL1815 and it is really composed of 2 batteries which are both rated at 15C. I am not sure if C-rating adds or stays the same when you are using two batteries. When I measure the Voltage on the test points I get 4.27V and when using a formula to find current for the Easy Driver I get 0.480A.

  • In what way is this related to the Arduino?
    – Nick Gammon
    Feb 17, 2016 at 6:40
  • An rating of 1.5Ah says nothing about the maximal output current of the battery. 1.5Ah states that it could (theoretically) deliver 1.5A over the course of one hour. You might want to re-check your battery pack specs. Since some may have a maximal discharge current rated well below that 1.5A. It's noted by the E-value, 1E would be 1.5A maximal discharge current in this case. (Probably not the problem here, but it's something)
    – aaa
    Feb 17, 2016 at 14:07
  • @Paul I couldn't find an E-value but I think that you meant C-rating because this is all I could find and it seems to be the same thing as what you're saying an E-value is.
    – lepton10
    Feb 17, 2016 at 15:39
  • C is charge rating, E should be discharge rating. I'm not quite sure if it's documented as so, or that they are generally the same value.
    – aaa
    Feb 17, 2016 at 16:48
  • The ratings of the battery are a longshot anyway. Probably not related to your problem, those accu-packs for makita are basically made for this. And the engine is the one heating up.
    – aaa
    Feb 17, 2016 at 17:29

1 Answer 1


How did you set the amps on the http://www.schmalzhaus.com/EasyDriver/ to 0.5A? What was the voltage at the test point? The EasyDriver v4.5 schematic says the formula for coil current is A = V/6. So rearranging, V=A*6, and to get 0.5A, the voltage should be 0.5*6=3V at the motor driver's test point.

The linked motor spec is 0.6A max per coil, and if things went wrong, you could have overloaded a motor. The 18V battery could have easily provided 1.8 amps to the 10ohm coil in the motor for a bit, before 3x the rated current of the coils would burn it out, or the easydriver went into thermal shutdown or something.

The easydriver looks like it would be capable of controlling the current adequately, but if misconfigured, could easily overcurrent the motor.

  • When I measure the voltage I get 4.27V. I used the potentiometer on the Easy Driver to adjust the current, and when using a formula I found online to find the current of the Easy Driver I get 0.480A
    – lepton10
    Feb 17, 2016 at 17:49
  • Try switching back to the situation that did work. To check if something got broken while trying to connect the other battery
    – aaa
    Feb 17, 2016 at 19:24
  • 1
    The schematic for the easyDriver v4.5 ( github.com/sparkfun/Easy_Driver/raw/master/Hardware/… ) says the formula is A=V/6 or 4.27/6=0.712A
    – Dave X
    Feb 17, 2016 at 19:46
  • Ahhh I see I think that I used a formula for a previous Easy Driver I'll try this out once a get a new stepper motor and see if this solves the issue. Thank you
    – lepton10
    Feb 17, 2016 at 20:37

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