It is easy to charge your phone in the albergues. However, you should always keep it in sight. A solar charger is not needed. Instead you can take a power bank that you charge at the albergue. Being less expensive than your phone, it is less of a risk to leave unattended, although that is still not a good idea. Take a charger with at least two USB ports so you can share the outlet or charge both your phone and power bank at the same time. During the day, if your phone battery runs low, you can plug in your charged power bank.