[MrForbes]

You could run the whole system with a small 12v battery, but don't expect to be able to run any motors that are under much physical load. Look at the motor specs in the Tips and Good Practices manual, they give the no-load current draw. Figure out how much current it will take to power those motors, and read up on how battery specifications work. You should be able to figure out about how long you can run some motors with different size batteries (assuming the motors are not mechanically connected to anything, they just spin freely). Perhaps a 12v nicad battery pack would do what you want, with less weight/inconvenience. Just make sure to use the appropriate charger for it.