Abstract: A portable solar battery charger comprises a photovoltaic array, a power regulator, a controller, and a battery. In one embodiment, the controller is configured to increase the charging current provided by the power regulator to the battery over time using discrete current levels. A comparator can compare the voltage of the photovoltaic array to a threshold, and provide the result to the controller. The controller can be configured to decrease the current to a previously selected level when the comparator indicates the voltage of the photovoltaic array is below a threshold, thereby improving the efficiency of the current delivery to the battery.

Abstract: Systems and methods are disclosed for current loss compensation in multi-junction photovoltaic cells. The use of direct electrical contact with the interconnect layers in a multi-junction PV cell can improve cell efficiency over variable lighting conditions. Electrical contact with some or all of the interconnect layers can advantageously permit disconnection of subcells operating at low current or voltage. The result is multi-junction PV cells that can adapt to variable lighting conditions and compensate for a decrease in current in certain subcells, thereby advantageously improving a multi-junction PV cell's total output current.