It would be difficult for the Energi to have a more minimalist design. It consists of just two parts: a gray-and-silver oblong battery holder and a short power connector. Energizer sells adapters for most Samsung, Sprint, Motorola, and Nokia handsets, while a USB version is available as well. Energizer claims that 80 percent of cell phone brands are supported, but we weren't able to find a connector for a Sony Ericsson.
To use the charger, you first must put the supplied lithium AA batteries into the holder. The cover is a bit tricky to pry off, but it's solidly constructed. Once the batteries are in place, insert the cord into the holder and plug the adapter into the phone. In our tests, within seconds, the blue light on the holder started flashing and our Samsung SGH-D357 started receiving a charge. When we started the test, the SGH-D357's was about 25 percent depleted, but it was fully charged after about 30 minutes.
The Energi is optimized to run on lithium batteries. You can use alkaline batteries as well, but they'll give only enough charge to make a few calls, or so Energizer says. Though we realize lithium batteries provide more power than alkaline, they also can be more expensive and harder to find. The Energi works with rechargeable batteries, too, but the idea of recharging batteries to recharge your cell phone just seems a bit silly.
Energizer hasn't published firm statistics on exactly how many charges a pair of lithium batteries are good for. Yet it does promise that the more complicated the phone, the fewer charges you'll get from the device. As a result, a smart phone will get no more than two full charges, while a basic phone can use the same lithium batteries several times. The length of time to charge a phone also varies, but it should be on a par with how long it takes to power a phone from a standard wall charger.