TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred System: In the solar based battery charging system above, the controller sequentially indicates the at least one battery so that battery having highest remaining voltage level is charged first. The batteries are discharged while powering the device based on one or more of sequence of charging of the batteries, number of charge discharge cycles that each of the batteries has gone through, and remaining life of each of the batteries. The controller indicates the at least one battery for charging or discharging so that none of the batteries of the battery system becomes non-functional due to non-charging. The batteries are connected in parallel, further where one or more of batteries connected in parallel have batteries connected in series to form a battery bank. The device is a light emitting diode (LED) cluster (110). Preferably, the solar panel is configured to detect day and/or night to indicate powering of the device; or the solar panel is configured to detect day and/or night to indicate charging and discharging of the batteries. The controller is configured to enable rotation of the batteries of the battery system for charging by the solar panel and for discharging by the device. The solar panel charges the batteries through maximum power point tracking charging system. It is positioned exterior to the battery system, further where the solar panel is adjusted based on an angle dependent on latitude and direction of sun. The controller is configured to sense partial failure of the battery system and partial or complete failure of the device and communicate the sensed failure through one or more communicating mechanisms. The battery system is charged using one or more of an external power supply, other batteries, or other renewable power generation mechanisms. Preferred Method: The method further comprises selecting the at least one battery for charging or discharging so that none of the batteries of the battery system becomes non-functional or goes into deep-discharge due to non-charging. The controller sequentially indicates the at least one battery for charging so that battery having highest remaining voltage level is charged first.