# Max limit of motors running at the same time

Has anyone tested or knows how many motors can be run at one time, assuming the motors all draw 1 amp, and using power expander?

If I remember correctly, the PTC in cortex is only 4A.
There are 2 PTCs in a cortex, and another PTC in power expander.

So that means total of 12A or 12 motors running at 1A each.

But of course this is a really simplistic calculation… without taking into account of spike currents, etc…

So it only applies to non-heavy loads?

All motors will have a surge or spike of current drawn when it starts turning… even if it is at no load.

Are you looking at what speed or power setting you should be using?
Then i would suggest that you look at the power curve of the motors.

Vamfun did quite a fair bit on this and has lots of resources on it too.

Our team is just wondering how many motors max should we be running at a time. So as long as we don’t start all of them at the same time, it should be fine?

You can start all 12 motors together.
Just make sure your power distribution is ok and you are not asking too much from each motors.

Most teams in NBN had ~10 motors running at some what high loads during skills or pre loads, so we know that much. Our team pushed it to 11 motors.

Many people “pushed it” to 12 motors.

Last year, our robot was fine having the 4-motor flywheel and 2-motor intake running while we were driving (4 more motors).

So like others have said, it should be fine, especially if you distribute the motors on different sides of the Cortex (ports 1-5 and 6-10) if you have mechanisms that would require some motors to need more current (i.e., they’re under more stress).

I agree with even however you will probably need to use a power expander to even out the load. The cortex has a rather whimpy power distribution setup [with equally whimpy motors]. What we did was throw half the drive motors on 1-5 and 6-10 and the other half on the power expander. You’ll have to think through what motors are drawing the most current, but with three places to split the power distribution into. I have not ran into any problems yet.