The LTC4070 allows simple charging of Li-Ion/Polymer batteries from very low current, intermittent or continuous charging sources. The 450nA to 50mA operating current makes charging possible from previously unusable sources. With the addition of an external pass device, shunt current may be boosted to 500mA. Stacked cell high voltage battery packs are inherently balanced with shunt charging. With its low operating current, the LTC4070 is well suited to charge thin film batteries in energy harvesting applications where charging sources may be intermittent or very low power. The unique architecture of the LTC4070 allows for an extremely simple battery charger solution; requiring just one external resistor.