A light atop the bag glows red to show electrical activity. It glowed even indoors, but take it outside for charging. The bag's three stiff, monocrystalline solar cells are supposed to pack more power into a smaller area as the amorphous, thin-film cells in the competing Reware Juice Bags. Yet Voltaic's cells feel flexible enough for natural movement when wearing the backpack, not nearly as rigid as they might appear. Voltaic also says its solar components withstand bending and heavy loads, while resisting tears from sharp objects. The cells are supposed to last 25 years and should also "self-heal" in the sun. If badly damaged, you can replace each 4-ounce cell for $30.
Taking advantage of the Voltaic Backpack's features isn't as easy as plugging in your devices and heading outside. You'll need to get to know some of its 16 parts. These include the battery with power out cable, five adapters, a car charger and socket, and an AC charger to power the battery from a wall outlet. Dealing with the many components is likely to turn off some users, but that's also true of other off-grid chargers, like the Solio and wind-powered HYmini.
At least Voltaic's adapters are thoughtfully labeled "Nokia," "Mini USB, "Samsung," and so forth. We dedicated one pocket to the many easy-to-lose parts, and left those we didn't need at home. Should you drop a piece off the edge of a cliff, replacements cost between $4 and $20 each at Voltaic's Web site.
We found that the solar panels took between 8 to 10 hours to charge the battery, as advertised. We charged a BlackBerry and several iPods each within about 5 hours, also as the company promised. Voltaic's rival, Reware, advertises shorter charging times for its bags, but they don't include batteries for storing power on the go.
On a cloudy day, you can hook up the Voltaic battery directly to the included AC charger or car charger. There are three voltage settings on the lithium ion battery, which is supposed to act as a surge protector to prevent "frying" devices plugged in at the wrong setting. To test that, we gulped, plugged in various devices at the wrong voltage, and nothing happened.
Service and support
We like the Voltaic Backpack's concise instruction booklet, which is small enough to keep in the bag for easy reference. We leaned heavily on it to get to know the bag's many moving parts, pockets, and power requirements. Still, we'd like step-by-step instructions for getting started, since we were initially overwhelmed by all the attachments. The battery alone has six features whose purposes won't be self-evident to most users. Free tech support is great, with a live person available via e-mail and a toll-free telephone number. A year-long warranty covers defects.
The Voltaic solar backpack isn't meant to replace indoor electrical outlets for keeping everyday gadgets fired up, but you could come to rely on its durability, comfort, and power on hiking, camping, or cycling trips. If ever lost in the woods, you'll appreciate the security of plugging in a GPS device or satellite phone.
If you were already planning to spend several hundred dollars on a backpack, then Voltaic's power features are an added value that make the purchase of a separate off-grid gadget charger, like the Solio or the , unnecessary.