What's 'in' a battery is energy, which is watt hours (there are other units). A battery's volts x amps x time gives the energy in a battery. A good alkaline D cell can supply more that 1 ampere hour at 1.5 volts or or 1.5 watt-hours of energy. Source(s): physicist/ electrical engineer. squeezie_1999 · 5 years ago.