A backpack is handy for carrying things around but how about one that can also charge your smartphone?

That's the promise of Powerbag, a backpack equipped with a built-in battery that is one of the thousands of new products going on display at the Consumer Electronics Show (CES) which opens in Las Vegas on Tuesday.

"It will charge all smartphones. It will charge all tablets, all e-readers, Bluetooth devices," Dan Kurzon, vice president of sales for Powerbag, said at a preview event for exhibitors at the annual high-tech gadget extravaganza.

"Let's say I have a bunch of devices," Kurzon said. "I have an iPhone, an iPad, a BlackBerry.

"I get to my hotel, I load up the bag with all those different devices and I plug it into the wall," he said. "It's going to charge up those devices and it's going to charge up the battery on the bag."

Powerbag began selling the battery-equipped bags in October and offers several different styles, from a standard backpack to a messenger bag with a single shoulder strap to a rolling briefcase.

Up to four mobile devices can be charged at once using the bags which feature 3000 mAh, 6000 mAh or 9000 mAh batteries depending on the style.

Powerbags, which are made by RFA Brands, start at $140 with the most expensive retailing for $250.