[BBray_T1296]

Originally Posted by Daniel_LaFleur

Just a word of caution: If you stall a CIM it pulls ~133A. If you stall a 6 CIM drive, it'll pull somewhere between 400-500% of the rated current for the main breaker (current being limited to the batteries internal resistance, I don't have that number in front of me right now). That will trip the main breaker in 1-6 seconds (as per the chart above). The 40A snap action breakers will be at ~ 250% of rated current and may take longer than the main breaker to pop (again I don't have the spec sheet in front of me) and that's not accounting for any other electrical load you have at that moment.

Basically, ensure your 6 CIM drivetrain is never in stall (make sure it's traction limited, not torque limited).

If each CIM were drawing 133A, a 6 CIM drive would pull 800 amps.
In addition to frying all 6 motor controllers, the plastic PDB would be molten as well. Your wires would be scalding to the touch, and there would be a large quantity of gaseous substance emitting from the robot. Basically, yes it is a bad thing, but no, it will practically never happen. This is really not something to worry about.

We ran a 6 CIM VexPro ballshifter running 3" wheels, and geared to 5.5fps and 15.5fps. In addition to bulldozing everyone we faced, we never blew a breaker once. That being said, we did have a "ramp up function" in the code. Basically, if you jammed the joystick into full forward, the code would automatically and linearly increase the PWM "throttle" very quickly (read: like 1/2 second) from 0 to 100%. Even when throwing the robot from full forward into full reverse, we never had a breaker-blowing situation. The acceleration time is negligible compared to instant-100% because the ramp up is so quick and you have the comfort of knowing whatever you could possibly do to that joystick will not disable the drivetrain. The ramp up has the advantage of suppressing the instantaneous current draw into a slightly longer duration but lower peak draw.