I have tried to develop a charger for a lithium battery (3.6v) circuit diagram attached, its rough and not to scale. The idea is the battery is charged using PWM (from a PIC) when the solar panel is generating between 1-4volts. The output of the solar panel is fed into a voltage tripler to supply the lithium with voltages between 4v to 18v. The solar panel is also fed to a PIC which adjust the PWM to achieve an average volatge of 4v across the battery. If the voltage exceeds 4v or drops under 1v the charging ceases.
I will also use a some thermal device to send info to the PIC so when the battery pack heats up hence battery overcharging the charging stops.
Do you guys think this will work? Im not to sure sending burts of high voltage to the lithium and not too sure about the reliability of the thermal device to detect overcharging