That will almost certainly need a much bigger panel. If a phone is a 3W constant load, that's 2232Wh in a month, except in summer there is no way a nominally 20W cheap PV panel will keep up with that from October to March at latitude 54. Combination of short daylight hours and overcast weather so rarely any direct sunlight.
The 20W rating is at what is called standard test conditions, basically equivalent to direct sunlight in the Arizona desert.
You'd probably want at least a nominal 180W panel and a basic 25 Euro PWM PV charge controller.
The 20W rating is at what is called standard test conditions, basically equivalent to direct sunlight in the Arizona desert.
You'd probably want at least a nominal 180W panel and a basic 25 Euro PWM PV charge controller.