A rechargeable Nickel Cadmium (NiCad) or Nickel Metal Hydride (NiMH) of the appropriate size can be used. However, rechargeable Lithium-ion (Li-ion) batteries cannot be used.  The battery voltage of a Lithium-ion battery is too high and can cause damage to the light.  This applies ONLY to products that are NOT Intrinsically Safe Certified.