A solar power system comprising a solar panel, a load, and a battery pack group. The load comprising an electric motor operatively coupled with a propeller. The battery pack group comprises one or more voltage controllable battery packs, each of said one or more voltage controllable battery packs comprising a plurality of battery cells. The voltage controllable battery packs having a rigid printed circuit board electrically coupled with the plurality of battery cells, the rigid printed circuit board including an interconnect connector to electrically couple with a corresponding interconnect connector of a second voltage controllable battery pack.