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LTC3105/LTC4071 2-Cell Solar Panel Li-Ion Battery Charger

2-Cell Solar Panel Li-Ion Battery Charger

This circuit shows a compact solar-powered battery charger using a LTC3105 as a boost converter and a LTC4071 as Li-Ion shunt charger. A 2-cell 400mW solar panel provides the input power to the LTC3105 to produce over 60mA of charge current in full sunlight. Maximum power point control prevents the solar panel voltage from dropping below the 750mV maximum power point. The LTC4071 shunt charger limits the voltage across the battery to 4.2V. To prevent battery damage from overdischarge, the low battery disconnect feature disconnects the battery from the load if the battery drops below 2.7V.