Patent ID: 7781902

Claim:
A generator set comprising: an internal combustion engine; a DC generator coupled to the engine and configured to produce direct current (“DC”) electricity; one or more battery cells configured to discharge stored DC electricity, the one or more battery cells operable to be recharged using DC electricity from the DC generator, wherein the one or more battery cells include a first group of battery cells and a second group of battery cells, wherein the first group of battery cells and the second group of battery cells are independently rechargeable, and wherein the first group of battery cells are configured to be relatively permanently integrated within the generator set and the second group of battery cells are configured to be removable from the generator set and compatible with a portable power tool; and an inverter electrically connected to the DC generator and to the one or more battery cells, the inverter configured to convert DC electricity produced by the DC generator and DC electricity discharged from the one or more battery cells to alternating current (“AC”) electricity, the AC electricity available for use by a load.