Quote Originally Posted by craig_colliass
I have used the sabertooth 25A controller on a 4 drill motor setup in Tron, it did all kinds of weird stuff so I never used that setup in the arena. The sabertooth is now in Seraphim and works very well that€™s with 2 12v Como drill motors running at 14.4v this is to be increased to 16.8v soon.
In Tron which has 4 9.6V drill motors running at 14.4V I now use a Sidwinder this grabs the motors by the scruff of the neck and throws Tron around the arena with no fuss at all. I agree with the rule with 4 drill motors in a feather the bigger the speed controller the better.
GENERALISATION.

A featherweight bot geared for 8 mph with 18v drill motors could ...under normal fighting conditions... pull 24 amps total....[ 4 motors = 6 amps each 2 motors = 12 amps each ]
with 12v motors 32 amps total
with 9.6v motors 44 amps total

gearing for 4 mph will halve the amps required......gear for 12mph and you would increase the amps required by 50%.

Speed Controllers with built in current limiters could / will current limit continiously if your bot is overgeared.

Note that stall amps per motor can be also excessive.

http://www.mabuchi-motor.co.jp/cgi-bin/search/e_use.cgi