Greetings 
With your setup using 0.5w Solar Panel 55x70 and 2A Li-Po Battery, how long it will run ?
Am already setup some rain data logger, but im stuck with powering.
Using panasonic 6V 4Ah i guess impossible to full charge.
Later day, i tried using an old/used lipo batt (900mAh) from SE-W960 (only run 5 hour standby in my phone)
And after full charge, it was run about 3 days. Already log the date, time, temp, and batt every 2 seconds. (4.25v till 2.67v batt volt)
It is enough for me, but i need it to run for 3 month.
Will the 0.5 Watt or 1 Watt solar panel sufficient for this task ?
The final project will include an extensometer using optical encoder (from old hp printer)
Thank you for your valued time, and sorry for my bad english.