Powering 12V High-Power (HP) 25D mm Gearmotor

Hi All,

So I am very new to this electronics hobby and trying to build a coffee grinder. I bought the [12V High-Power (HP) 25D mm Gearmotor] and connected it to a portable hand grinder. I have the motor hooked up to a variable power source so I can push 12V no problem but when I pour in a single coffee bean, the motor stalls and the current reads about 0.5A. I am sure I am misunderstanding this but I thought the stall current on the motor spec (https://www.pololu.com/category/186/12v-high-power-hp-25d-mm-gearmotors) was 5.7 Amps. With no load, it runs at about 0.17Amps. I measured the torque needed to grind the coffee to be 160oz-in so the specd torque should be enough and the power source can supply up to 24V/4 Amps so I should be good on power supply. My only thoughts are maybe the thin 22 AWG wire is too thin to support that current.

Any other thoughts on why I am stalling out when the motor should be almost double to torque needed? (240 oz-in speed vs 160 oz-in needed)

Any input is much appreciated!


Based on the stall torque you provided, it sounds like you might be using our 75:1 Metal Gearmotor 25Dx54L mm HP 12V. However, many of our 25D gearmotors appear identical. so can you confirm what product you have and post its product number or a link to it? If you happen to still have your packaging the motor came in you could check the label, or if you ordered from us you can login to your account on our website and check your order history.

Can you also tell me how you are measuring your motor’s current draw? Posting some pictures and a video of your setup in action would also be helpful. The forum does not allow users to post very large videos, but it does work well with videos linked from other sites (like YouTube or Vimeo). If you entirely remove the motor from your setup and try to power it, does anything about its behavior change (e.g. free-run current or speed)?

By the way, if your motor’s extrapolated stall torque is 240oz•in, then I expect regular 160oz•in loads to overload it and greatly decrease its lifetimes or even cause immediate damage. The recommendation we include on the product pages for our brushed DC metal gearmotors is to operate at or below 25% of stall current (which corresponds to 25% of stall torque when running at the nominal voltage).

- Patrick