Powering a stepper motor 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.
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.