DIY Solar Shack
Solar Panel Sizing
You need to know: how much energy needs replacing in the battery battery voltage solar output in your area
How do you know how much is left in a battery?
How to estimate remaining battery capacity
It's All In The Voltage
If solar panel more than 5 watts use a charge controller
MPPT controllers are 30% more efficient than PWM
Irradiance varies by location, average value is 4 peak-sun-hours/day
Measure battery volts to find Depth of Discharge
Solar panel power depends on the sun's energy in peak-sun-hours/day - this is irradiance
ALWAYS use a controller!