# Doubt in choosing the right DC motor?

Take this motor as an example - https://www.robotshop.com/en/12v-100rpm-583-oz-in-brushed-dc-motor.html

it has torque of 42kg.cm

I know all the calculation to find the payload of dc motor from here - https://www.quora.com/How-do-I-calculate-how-much-weight-can-DC-motor-carry

My main concern is the output power. Power formula is:-

power = voltage x Stall Current = 12 x 2A = 24W

But the specification says that the power is 5W. Which value should I use in my calculation?

• Do the same calculation with the rated values. What do you get? – Majenko Dec 25 '18 at 15:30
• then the value is too low, I want to make a mobile robot whose weight is 5kg. I want to use 2 dc motor for this project. – Sultan Morbiwala Dec 25 '18 at 15:58
• The stall current tells that the driver should be able to give that current or else the driver will get damaged. The 24W is only a calculation. I assume that the maximum mechanical power will be a few watts less. The 5W power is probably an average for normal operation. Perhaps the motor and gears are not designed to operate a long time near the stall current. Perhaps the motor gets too hot if used for a long time with more than 5W. – Jot Dec 25 '18 at 17:17

With a current rating of `0.68 A` at `12 V` you get the normal power requirement of `8.6 W` for a `7Kg.cm` torque.
If, for any reason, you stall the motor, your driver must be capable to output `2.2 A` or `26.5 W` to avoid a permanent damage.