I’ve been carrying the original Solio Classic on big walls for many years. I’d hang it from a belay bolt, make sure its three solar pedals faced the sun directly, and, in a few hours voilà! I had power to recharge that crusty old iPod when needed.

Then I got an iPhone and the Classic didn’t produce the right amount of power and I had to –gasp! – climb big walls without endless tuneage.

Enter the Classic 2 ($100). It’s slimmer than the original model, has broader sun pedals (measuring 5.8in x 2.8in. x 1.4in – 10.1 oz.) and its 3.7V 3200mAh lithium-ion battery has twice the capacity of the previous model. Solio’s website claims “a full day of sun provides three full charges for portable electronic devices, and “one hour of direct sunlight provides one hour of use.” I haven’t been able to get that much power out of my charges – because I haven’t spent the whole day in the sun — but I have been able to partially charge two iPhones after a morning and early afternoon of lounging on top of El Cap. (Note: the Classic 2 was completely uncharged before I placed it in the sun.)

Alternately, I charge the Classic 2 using an AC outlet by fastening the provided USB cable to my iPhone AC jack. The 1 amp output means it charges smartphones at the same rate as a wall charger.

It takes 6 hours to fully charge the Classic 2 by way of AC or USB. It holds a charge for up to one year. The Classic 2 can be recharged for approximately three years before the battery no longer holds a charge.

Another handy perk of the Classic 2 is that it provides power on the go. I carry it on long bike rides to keep my phone charged while running the battery-taxing GPS app called MapMyRide. Sometimes I’m in a rush to get out the door and can’t wait for my phone to fully recharge. In those cases, I just pack the Classic 2, plug it into the phone via the iPhone’s provided USB cable and keep them both in the front pocket of my shorts.

If you stick a pencil through the hole in the middle of the Classic 2 then you can position it directly to the sun. Instead of doing this, I just lean it against a shoe, sweatshirt, or rock but come to think of it the pencil is probably a better idea. The website says: “Simply point the Classic 2 towards the sun and rotate it until the pencil no longer casts a shadow. Adjust the position of the Classic 2 each time the pencil casts a shadow for maximum solar capture efficiency.” Reading directions, what a novel idea.

To turn it on, i.e., to charge your smartphone, you must click the clear button on the backside of the Classic 2. Once on, it starts blinking indicating its charging the device, but sometimes I can’t get it to stop charging. I’ve depressed the button like the directions say, but it doesn’t always turn off.

I carry the Classic 2 with me almost constantly, it provides backup power when needed and can be charged in a variety of ways.

Specs from solio.com below:

1 full Classic 2 battery provides the following power:

15 hours of Talk Time or 675 hours Standby Time based on iPhone 4

15 hours of Talk Time or 616 hours Standby Time based on Motorola Droid

11 hours of Talk Time or 3103 hours of Standby Time based on HTC EVO

137 hours of music or 24 hours of video based on iPod Touch 4th Gen

8 hours of operation based on Garmin Nuvi 850

$100, store.solio.com