A camera having a photovoltaic cell such as a solar cell is provided. A power supply circuit of a camera comprises a solar battery, a second battery and a switch. If the second battery is a secondary battery, the switch is closed to connect the solar and second batteries in parallel. Otherwise, the switch...http://www.google.com/patents/US4494854?utm_source=gb-gplus-sharePatent US4494854 - Energy saving camera
