I prefer paper maps. You can toss them or mail them home when you're done with a section. On certain tours I've printed off all of my maps beforehand and mailed them to points along the way so I was only carrying so many at a time. If you skip a point where you mailed them find a library and print off new ones for your new section. As Jamawani said, they always work, never have to worry about a signal or charge them.
As for electronics; Buy a cheap external portable battery backup. I bought a $30 one off of Overstock.com to recharged my iPhone 6 while on tour. I would get 4 or 5 full charges out of it before it needed to be recharged. You can charge your phone while charging the external battery too. With MapMyRide running in the background and all other applications closed I would get 2 days out of my phone before needing to charge it. This included using it to take photos. Otherwise, you can always charge at campgrounds, cafes etc!