Hi! New to the forum and Odrive. I’m working on a robotics application that will require pretty high torque. I purchased the M8325s kit with s1 and I’m blown away with the quality and interface. I read that the motor at 40A continuous current can support 3.31 NM.
My motor design is similar to the MIT mini cheetah (QDD) but with a 1:25 gear ratio through a two stage planetary (1:5) gear drive (sso not really quasi at that ratio, but maybe quasi quasi). So far so good! I want to start pushing the design (25 * 3NM = 75NM), but I’ve realized that I’ll cap out on current. I’m currently using the 48V 600W (12.5A) Mean-Well power supply. Given that it will cap at about a quarter of the continuous current capability of the M8325s I’m guessing I’ll need to upgrade. Are there any recommendations for pushing the M8325s? What was used to test the 40A spec?
My ideas were: find a used go-kart, bike, or server battery?
Gang a few smaller power supplies together with Diode ORing circuits?
Would love thoughts! Thanks!
Glad to hear the ODrive is working out for you!
Note that power supply current != motor current: Things in Motion: How to select the right power source for a hobby BLDC (PMSM) motor. For instance, if your motor’s at zero speed, then 12.5A at 48V (600W) from the power supply corresponds to 130A at the motor! You can set an active bus current or power limit via the active power limit feature – so you can take full advantage of your supply’s power output no matter the operating point. Note also the 600W Mean-Well we supply is designed to peak at higher currents: https://www.meanwell.com/webapp/product/search.aspx?prod=LRS-600N2
The 40A limit on the M8325s is the maximum continuous current the motor can take in free air, however it can definitely go much higher in transients. Note though that at 48V, the S1 has about a 40A current limit, see here: ODrive S1 Datasheet — ODrive Documentation 0.6.10 documentation
One option would be to run the system at a lower voltage, anywhere under 34-36V or so will allow 80A continuous from the S1, at the expense of maximum motor speed (see here for a calculator/graph: ODrive Motors — ODrive Documentation 0.6.10 documentation).
