Torque vs. weight vs. battery life — the honest trade-offs behind picking a motor for the ring.
A sumo bot is a torque problem wearing a robot costume. The league rules cap the weight, so every gram you spend on motors is a gram you cannot spend on chassis, wheels or battery.
N20 gear motors with a high reduction give the push you need, but they draw more current under stall — which is exactly when you need them. Choose a motor driver that can handle that stall current with margin, or the first serious push will kill your board.
Battery is the quiet third wheel. A LiPo that can deliver the stall current without voltage sag keeps your driver and control loop honest in the last ten seconds of a match.
The honest process: pick the motor that clears the weight class first, then let the driver and battery follow the stall current.