The E1 has a small 12v battery to run the instruments, lights etc. You can't connect a light bar to the Discover Dry Cell batteries. Individually, they are 6 volts, but there's eight of them in series to make 48 volts that runs the motor. In the battery compartment under the seat, you'll see the dry cell batteries, but also a smaller ATV-type 12v battery directly underneath where you sit to drive. There's a fuse and relay box down there too. I'd recommend not fiddling around in there unless you're absolutely sure what you're doing, as the 48v system could cause you a nasty injury if you short it by mistake.
On the UK version, there's a 12v accessory point in the dash along with all the control buttons. There's also a 12v supply to the registration plate light on the underside of the tilting load bed. Either of those should be safe to tap into for a light bar, and are only live when the ignition is on.