for charging phones, I use USB chargers connected to my trailer's 12V system. I also have a '400W' (really, 200W continuous) portable inverter that I plug into a powerpole socket that I installed on said trailer 12v system for charging things that need 120V.
my trailer has dual GC-2 golf cart batteries, which give me 210 amp*hours at 12V. assuming no more than 50% discharge, thats about 1200 watt*hours useful power. there's a 160 watt solar system on the roof so parked in the open on sunny days, I'm pretty sure I get at least 1000 watt*hours back into the system.