A Phone Good to 2027 on One Charge How long the battery lasts in a phone when you aren't using it is called standby time, and is usually measured in days or, in the case of a battery life champ like the Droid RAZR Maxx, about two weeks. But the $70 SpareOne emergency phone from Xpal Power, which uses a standard AA lithium battery, claims a standby time of up to 15 years. Although the phone is a lightweight plastic, it doesn't feel cheap. It's a really pleasing little design, with a curvy two-tone case and a window front and back that lets you see the battery. The phone has only the barest of features. No text, no Web, just phone calls and a dedicated 911 button. Indicators, like if you have a network connection, are provided by blinking colored lights. It saves a lot of power, but you'll have to memorize what the color combinations mean. The phone doesn't even come with a SIM card, which you will need before you can use it, although you can make a 911 call using the emergency button even without the SIM card. The phone is built for a GSM network, which means that in the United States it will work with T-Mobile, AT&T or companies that resell those networks. SIM cards are cheap. I see them online for less than $10 -- or even free -- but you still have to buy service. For my emergency phone, I spent $100 for 1,000 T-Mobile minutes, which are good for one year. I top it off annually, which extends my remaining minutes for another year. So after the first year, I can maintain coverage for about $10 a year. Calls on the SpareOne weren't crystal clear, but they were certainly good enough for roadside assistance to hear where to send the truck. As for the claim of 15 years standby time, I'll let you know in 2027.