While it may not be breaking news, Windows phones can suck a battery dry with heavy use. Travel chargers and extended batteries help. But what happens when you're away from a car or wall outlet and you see the "battery low" warning pop up on your screen? For some, Motorola may have the answer with their P790 Portable Charger.

The compact charger is a 1700mAh battery that can be used to recharge your Windows phone or be used as an external power source. It's not for all devices, so ease on past the break to read more about the P790.

Design

The P790 measures 2.9 inches long, 2 inches wide and 0.9 inches think. It weighs no more than your average Windows phone battery at 2.8 ounces. It reminds me of a beefy pager, compact enough for a pocket and won't take up much room in a briefcase, backpack or purse.

The design is simple. A female miniUSB port is on one end and a expendable male miniUSB port is on the other. A slide is on top of the charger to extend/retract the mini-usb end. A LED light is also on the top to show charging status/level.

Compatibility

While the Motorola P790 was designed for Motorola products, it is compatible with other devices that use a miniUSB connector. Motorola dubs these connectors miniUSB, but they are crimped slightly on the sides giving them a unique enough design to cause compatibility issues. While I could attach the P790 to my AT&T Tilt2, I couldn't charge the P790 with my HTC charger because the crimps.

I also found that you can use a miniUSB to microUSB adapter to fit the P790 to phones such as the Motorola Q and Treo Pro.

Performance

Motorola reports the P790 to provide an additional 300 to 400 minutes of talk time to devices such as the Motorola RAZR. While Motorola doesn't offer any stats on how the P790 impacts other phones, unless your using a battery smaller than 1700mAh, it should at least double your performance.

The P790 also is compatible with some Motorola Bluetooth headsets. These batteries are considerably smaller than a phone's battery, so the P790 should easily double, triple or quadruple a BT headsets battery life. Motorola claims it could provide more than ten full charges to a BT headset.

Overall Impression

The Motorola P790 portable charger is an attractive, sharp-looking device, but it's limited to Windows Phones with miniUSB ports. Phones with proprietary ports (e.g. Samsung) won't be compatible with the P790.

It's compact, light weight and does provide a considerable amount of juice to your battery. I can see it coming in handy for camping trips, long plane/train rides, or other situations where outlet power sources are not available.

At $19.95 the P790 is modestly priced, but I'd be inclined to look at the Cellet Emergency Charger first if you need an emergency or extended battery source. While the P790 worked fine with my Tilt2, it is designed for Motorola products. My HTC charger was of no use in charging the P790 and, luckily, I had a Motorola charger to use. The Cellet is alkaline battery based and might help you avoid any compatibility issues.