There are several ways of providing backup power.. I have added batteries to my uninterruptable power supply. I've wired them in parallel, and I put switches on each battery. When the batteries need to be charged, I allow the one built into the UPS to charge first, then I flip a switch to charge the next battery. I keep doing this until all the batteries are charged. My system remained operational for over a day and a half. However, like another poster suggested, there is more than one way to provide for power in a prolonged emergency. Routers, modems, VOIP phones, many FXO's, and laptop computers are low voltage devices that can be powered by the sun and wind without too high of a cost or installation effort. For cell phone, one can pick up solar powered cell phone chargers very cheaply.