Calculating stall current ish

I am trying to figure out how to calculate the stall current of my drive motor. I have tried using my multi meter but it only goes up to 10 amps. I did see almost 13a before the fuse blew though. The motor itself is from a power wheels and says it has a continuous current of 13a, and I believe the rmps where either 2000 or 1500 there is not much info on the motor itself, I measured the resistance of the motor by putting the muliti meter between the + and - and got 1.1 ohms.

   I have just purchased a 24v23 and want to make sure that the stall current isn't going to be an issue. The project it is going in to is a R/C wagon that my kids can ride in, on the high side it might have to move 150lbs up hill. I also plan on putting heat sinks and fans on the boards as well.


I was told by a teacher that if I took the lowest total resistance of the motor (I just read the ohms across the motor leads and slowly incremented the motor) I could divide the Vin by that value and get a worst case scenario. I read the lowest @ .7 ohms or 700mohms my Vin is 12 v which puts it at about 17A so the 24v23 is well above these rating but what I am more worried about is the motor kick when it is first turned on is there a way to combat this by maybe using a M.O.V. (metal oxide varistor, )or some sort of current limiter of sorts I am worried about burning up the board I know they aren’t much money but when you have to kids the wife is not going to be happy if I burn it up in the first week. Anyone have suggestions, comments, anything would be helpful.


Measuring the resistance of the motor is a good first approximation. However, in general it is difficult to measure small resistances accurately. A better way is to measure the amount of current that is drawn at some voltage and compute the resistance. Try stalling the motor at some small voltage and measure both the current that it draws and the voltage drop across the motor (this might be less than your unloaded supply voltage if the current draw causes the supply voltage to drop). With those values you can compute the resistance using Ohm’s law, and then use this in turn to calculate the stall current at higher voltages.

With the load you described, and the readings you have to date, I suspect the stall current of your motor will be more than what the 24V23 can handle.