The required voltage is 3V DC, need two 1.5V batteries in series as Mark stated. A simple two-cell plastic holder works fine, I recommend using D cells for longer run time. If the clock will not wind on 3V there are a number of potential problems such as burned contacts, an open circuit somewhere in the solenoid coils or elsewhere, etc. You will need a reasonably good volt-ohm meter to analyze where the problems are. There are several members who should be able to help get you started checking it out, hopefully they will be along soon.