NEW YORK ( TheStreet) -- When it comes to small-business mobile devices, one word says it all: Charge!For all the productivity fruit smartphones such as the Apple ( AAPL) iPhone 4, Motorola ( MOT) Droid X and Blackberry ( RIMM) Torch 9800 yield, the little worm called battery life is happily eating away at those gains. Why? Four-inch screens, phat 1 gigabyte processors and power-thirsty 3G/4G cellular networks all need electrons, and lots of 'em. So these wonder units are lucky to last through a day of real work. Some, such as the HTC EVO from Sprint ( S), can go flat after just a few hours. True to free-market form, third-party vendors have taken notice of the thirst for portable power. And a whole generation of battery backup tools have started to school in the cellular waters. Here is the skinny on what you need to know for portable battery backups as you gear up for last-gasp, end-of-summer travel. Solio Mono ($60) Call me a sucker for solar, but there is no better feeling than making money completely free of the miserable disgrace that is our domestic power grid. And Better Energy Systems' Solio Mono charger is the current best solar step. Charge the internal battery via a wall socket, USB connector or built-in solar panel. This panel is smallish, so it can take several hours for a decent phone to fully charge. But the Mono stores juice for a year, so you can load it and forget it. Love that. Duracell Instant USB Charger ($35) For basic wall-charged backup, it is tough to beat what Duracell is doing in portable power units. Simply connect this sucker into any USB port, either via a PC or wall outlet adaptor, and it can store 1,135 milliamps -- enough to keep your average Motorola Droid running for about 12 hours. That is devilishly handy.