Rating: 4 / 5
Capacity: 4 AA's in 10 hrs, 2AA's in 5 hrs.
Weight: 4.5 oz.
Batteries Charged: up to four AA/AAA NIMH, the AAA's require the use of AAA adapters. Two are supplied with the unit.
Price: $99 (discounts available at some EBay stores)
Not everyone has a need for a power generating station on the trail, but the growing number of personal electrical devices will pique the interest of at least some long distance hikers who want to keep their phone, PDA, iPods, camera and headlamp batteries topped off.
After looking at several solar chargers, I chose the Silva for it's light weight and solar cell type. It's a flexible polymer solar panel which makes it less susceptible to damage from dropping or other abuse it's likely to encounter when strapped to a backpack. It has a built-in charge controller with LED status indicators.
The weight figure may need adjusting depending on your needs especially if your appliances don't use NIMH batteries. For example, only my headlamp uses NIMH's, every thing else requires 5 volts from a USB connector so I had to add two AA cells (2 oz.) to power a USB compatible charger (1.25 oz.) Even so, it's the lightest complete solution I could find.
How well does it perform? I'm just back from hiking the Cranberry 50 Loop in the Adirondacks where my photo and video production drew my camera battery down to 25% charge every day. I was able to glean enough power on this heavily shaded trail to fully or nearly fully charge the camera battery daily.
There was no phone service. Had I needed to charge my phone, I might have needed to curtail my picture taking. There was so little light in that temperate rain forest that most of the charging was during meals and breaks when I was able to place my pack in a pool of sunlight. On other hikes in less shady conditions, charging was faster even when there was an overcast.
I'm generally satisfied with with this charger. It's light and easy to use, and with care, can supply my electrical needs. Even when it can't do the whole job, I can at least count on it to give me enough talk time to get out an emergency phone call.
I down rated it to a four because the battery holder broke shortly after I started using it. I didn't bother sending it in for repair, opting to fix it myself. Anyway, I don't blame Silva too much. They don't make the holder, it's one of those ubiquitous OEM plastic AA battery holders.