The LTC4015’s input undervoltage current loop or UVCL can be engaged to help keep the input voltage from decreasing beyond a minimum voltage when a resistive cable or power limited supply such as a solar panel is providing input power to the LTC4015. A maximum power point or MPPT algorithm using this control loop has been preprogrammed into the LTC4015 to maximize power extraction from solar panels and other resistive sources, enabling maximum charge current to the battery.