I got a Sunpro voltmeter from my local auto supply store and a six position rotary switch from radio shack and intalled them in the cutouts under the seat of my xm-3000. The meter happens to be a perfect fit over the cutout. Once I get it wired up I'll be able to check the voltage on each battery individually just by a turn of the dial. The voltmeter even lights up so I can read it in the dark. The batteries are numbered in the order they are wired with the battery closest to the front of the scooter being number one. The sixth position of the switch leaves the meter disconnected from all the batteries and turns the light off. Pretty neat, huh? The switch will be wired to the batteries through a connector so the seat compartment won't be tied to the batteries. I moved the circuit breaker out from inside the compartment for the same reason. I have it taped to the side of a battery for now until I rig a mounting bracket for it.