PRODUCT REVIEW
Backup Batteries Give Your iPhone Extra Juice

That makes this an apt time to take a fresh look at an increasingly important part of our gadget portfolio, those portable charging devices that provide a shot of juice in a pinch.

Backup Power

Do you know someone seemingly at the edge of disaster because of a misplaced phone charger? Or maybe, after a nap with the music on during a lengthy plane ride, you find you don't have enough power to call the office ?

The iPhone 3G magnifies such issues. The WiFi connection, the faster network speeds and GPS (Global Positioning System) features all strain the battery. So for the last week, I've been using a few portable chargers to keep the iPhone and some other gadgets ready to go.

These devices are not intended to replace a proper charger. Rather, they should be viewed as an auxiliary power source for when the battery runs low and business needs to get done.

AAA Refresh

"It provides a supplemental charge," Ken Klarfeld, iPowerRush president, said of his portable charging device, one of the first targeting the iPhone 3G. "You're on a plane, watching a movie and your iPhone goes dead? What do you do?"

With the iPowerRush, you should be fine -- as long as the six AAA batteries it needs work.

In my tests, it provided what Klarfeld noted, a supplemental charge. The iPhone battery was nearly dead when I plugged the iPowerRush into the iPhone. About 45 minutes later, I had enough power to make it home, a 30-minute commute, playing with the iPhone all the way.

Once home, I plugged the iPhone into its charger. It should be noted that Apple's (Nasdaq: AAPL) new iPhone charger is about the size of a marshmallow, making it a portable power source. But it still needs to be plugged into a wall socket.

The iPowerRush, sold online for US$30 empties those six AAA pretty quickly, so it could become pricey if you use it too much. Even with fresh batteries, the device will not provide a full charge to the iPhone.

You can use rechargeable batteries -- remember to recharge those -- as well.

Hot Tip

Another approach is a portable charger with multiple connectors, or "tips." These tips are made for iPods, various mobile phones, digital mobile phones and countless other gadgets.

One of my favorites is the Powerstick, a $70 device that includes nine tips. I've used them for many of my own gadgets, as well as those I review. It always works -- and sure enough one of the tips it ships with worked with the iPhone 3G.

Again, the iPhone was nearly empty when I connected the Powerstick. It didn't fully charge the device, but it provided a longer charge than the iPowerRush.

You recharge the Powerstick via USB (Universal Serial Bus), so when it's empty, you simply plug it into a computer's USB port. A recharge takes about 30 minutes.

A Little Unreliable

But not all devices that claim to work with the iPhone will. The packaging on the Lenmar PowerPort Mini says it works with iPhones, but it wouldn't charge my iPhone 3G. It did charge an iPod nano and it claims to works with BlackBerries, but I didn't test that.

The PowerPort Mini is a cleverly designed device, small and affordable (several online retailers offer it for about $22). Like the Powerstick, it charges itself via USB and it fully charged an empty nano with juice to spare.

But I'm leery of this device, and it is not recommended. There were times it wouldn't work at all, even on that same nano. There's no point in buying an unreliable backup.

The Power of Portability

Finally, Duracell has refreshed its line of battery-based portable chargers. It sells two versions of My Pocket Charger, one for iPods (not iPhones) and for mobile phones made by Research In Motion (Nasdaq: RIMM) and Motorola (NYSE: MOT) .

It comes with two AA batteries, and an online price check found both versions starting around $15. It did fully charge an empty nano, but it does not work with rechargeable batteries.

Again, these portable chargers are great for a power pinch. I also think they are ideal gifts for road warriors, particular the Powerstick. It's the most expensive, yet the most reliable and flexible.

But due to the iPhone 3G's rapid popularity and even faster battery drainage, expect to see more power options quickly.