[techhelpbb]

If simulating the power supply of the battery is a concern with a power supply please keep in mind that you'd have to simulate the battery's internal resistance characteristics.

Even if you could get a power supply that could withstand the surge currents that battery is cable of (I have some really big power supplies and battery chargers with high current engine start functions) chances are high that the output of the power supply will have different impedance than the battery meaning that the motors under various conditions might behave differently.

On a slightly different note if the issue is just constantly swapping batteries and since you don't mind the cord perhaps you could rig up a charger for the battery with a switch / relay / contactor / MOSFET to disconnect and reconnect the charger more quickly or automatically in between using the robot.

Then the battery is no different than during competition, but the charging of that battery will be more consistent. Unfortunately then you're tethered to the wall socket.