Quote:
Originally Posted by Michael Hill
Well....stall current is kinda stall current. The stall current per motor for 4 motors is slightly different than the stall current for 6 motors. Stall current for a 6 CIM system is about 75 Amps/motor and the stall current for a 4 CIM system is about 87.5 Amps/motor. This is because when you add more CIMs, the motor voltage will decrease. This voltage can drop to about 7.5-8 volts when stalling. The stall current cited in the CIM motor documentation (~131 Amps) is assuming the voltage is a constant 12 volts (not what we see in robots). It is correct that friction is what limits the stall current. Also, note that there's a difference between the static friction and kinetic coefficient of friction. In fact, you can even have just as much pushing power with a 4 CIM drive as a 6 CIM drive (if geared properly).
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I am aware that the voltage can drop down to 8 volts for brief instants in time, but does it stay down this low for extended periods during a pushing match? I will have to remember to check the driver station data logs next time I have access to the driving laptop.
I had always thought that, for things like pushing matches, voltage briefly dropped down to ~8 volts but then jumped back up to some value around 12. The battery should be applying a relatively constant voltage, so I don't see why the voltage would remain notably lower for any extended period of time.
So yes, the stall current might be ~90 amps for short periods of time, but I am thinking that the stall current is much closer to 130 amps for most of the time in a pushing match.