Solar charging of batteries has recently become very popular. A solar cell's typical voltage is 0.7 V. Many panels have eight cells in series and are therefore capable of producing 5.6 V at most. This voltage is adequate for charging a single Li-ion battery, such as that used in cell phones, to 4.2 V with a buck or step-down charger. However, using the same panel to charge a multicell Li-ion battery like that used in laptop computers requires a boost or step-up charger. This paper identifies the key concerns in implementing such a modification and provides a design example that uses the Texas Instruments bq24650 solar battery charger.
TI, Texas Instruments, battery charger, solar