A quick look at SolarFocus' Solar Mio Pro USB charger


Solar power for the zombie apocalypse
— 10:47 PM on August 8, 2013

Are you prepared for the zombie apocalypse? I know I am. Every year, my girl and I spend up to a full week engaged in a zombie preparedness drill. She thinks we're just camping, but I'm quietly honing our escape and survival plans. Densely populated areas can too easily become overrun with walkers, so we pile into a kayak and set out for a remote coastal island. The currents along the west coast of British Columbia are strong enough to keep undead swimmers at bay—I hope.

We only bring the essentials on these trips: food, shelter, clothing, and lots of wine. A Lobo would be too conspicuous, but a double-bladed kayak paddle is a decent substitute. The Star Wars kid has nothing on my sweet decapitation moves.

In recent years, smartphones and tablets have also come along for the ride. Unlike those who would prefer to keep the outdoors free of electronics, I think mobile devices are ideal companions in the wilderness . . . provided you don't let Angry Birds distract you from the real ones. GPS functionality makes portable computers great for mapping, and it's nice to be able to tote a massive library of books and comics in a single, easily portable device.

Battery life is an issue, of course. There are no wall sockets in the wild, and the grid will probably black out quickly if the undead rise. Portable power packs can provide a quick charge or two, but something sustainable is required for long-term survival. Right now, my solution is SolarFocus' Solar Mio Pro.

The Solar Mio Pro is basically a USB power pack with a solar-charging sidekick. I've been playing around with the thing for a few months, and it recently accompanied me on a week-long excursion off the west coast of Vancouver Island.

Making room for the Solar Mio Pro was easy. The battery measures only 3.1" x 3.4" x 0.6" and weighs a scant 0.2 lbs. The solar component tips the scales at 0.6 lbs and folds up to be just 8.7" x 3.3" x 1.4". The whole package is light enough for backpacking, and it's small enough to tuck easily into a bag. Heck, I can fit the entire thing into some of my jacket pockets.

When unfurled, the solar array covers 18.1" x 8.7" and ends up being just 0.2" thick. Six individual panels are set into a rugged fabric sheet that can be laid flat or curved to stand vertically. Small loops at the corners allow the array to be tied down or strung up, as well. You should have no problem positioning it for maximum exposure.

The solar array feels robust overall. In addition to being surrounded by tough fabric, the panels have a scratch-resistant polymer coating that allows them to flex. Don't get the Solar Mio Pro wet, though. SolarFocus warns against exposing the unit to "rain or moisture."

Staying dry is no easy task off the west coast of Vancouver Island, even during the height of summer. This year, our stretch of deserted island beaches was routinely socked in by a fog so wet the trees drizzled. A few drops fell from the clouds, too, and the solar array endured the light dusting with seemingly no ill effects. The battery was kept in a waterproof bag throughout, though. SolarFocus provides a bag large enough for the battery and associated power adapters, but the solar array won't fit whether it's folded or not.

Rainy days aren't ideal for basking in the sun's rays, so the Solar Mio Pro's aversion to water isn't a huge inconvenience. At least the solar panels are still capable of juicing the battery when the sun is obscured by fog and cloud. SolarFocus claims the power pack will typically charge in 8-10 hours with 60% cloud cover. Under direct sunlight, the charging time is listed as 4-6 hours. Those estimates generally match my experiences in the real world. I managed to charge the battery fully over the course of a day when the sun never burned brighter than a vague, hazy dot in the overcast.

Each solar panel uses three silicon photovoltaic layers to extract energy from red, green, and blue photons separately. The layers employ slightly different silicon alloys and optical gaps. At the bottom, a reflective oxide layer bounces the remaining photons back up, giving the solar cells a second crack at absorption. SolarFocus claims this design yields broad spectrum coverage and high output.

High output, in this case, is a maximum of 600 mA at 6V. You can't charge devices directly using the solar array, though. Instead, the solar array charges the power pack, which can then be used to fuel devices. This two-step process enables device charging after sundown. However, it also slows the process of transforming sunlight into usable energy for devices. Another limitation: the power pack can't charge devices while simultaneously being replenished by the solar array. At least you can skip the solar business and charge the Mio's battery directly from a PC's USB port.

Inside the power pack's plastic body sits a 3.7V lithium-polymer battery rated for 2650 mAh. 5V output is available at up to 1A, which is enough current to charge most smartphones and some tablets. The Nexus 7 and iPad 3 worked without issue. However, I couldn't get any of Asus' Transformer convertibles to charge from the power pack.

The Solar Mio Pro's output flows from a standard USB connector that can be combined with your own cabling or one of nearly a dozen included smartphone adapters. A standard Micro USB jack is among them, of course. There's also a clip-on charger that connects directly to 3.6-3.7V batteries. The charger has adjustable clips to accommodate +/- terminals up to 22 mm apart, and I had no problem attaching it to the battery from my waterproof camera. Too bad my DSLR's battery is incompatible.

With a relatively modest 10 Wh payload, the Solar Mio Pro won't fill a tablet. Our Nexus 7 went from completely dead to only 38% battery life after fully draining the Mio's power pack. For me, the limited capacity isn't a big hindrance. Smartphones and tablets are nice to have in the wild, but there's no reason to spend a lot of time using them. 38% on the Nexus 7 is good for a few hours of usage, at least.

For those who require moar power, SolarFocus makes beefier SolarSupra models with additional panels, bigger batteries, and an AC output options. They don't seem to be for sale online, though. Right now, you can grab the Solar Mio Pro for $125 on Amazon. That seems reasonable given the charger's capabilities and the generous collection of included adapters. PowerFilm's $75 USB+AA Solar Charger looks like an intriguing alternative, but its solar component is weaker, and its USB output current appears to be half that of the Mio. PowerFilm's cheapest solar product to officially support tablets is the $190 F15-600, which lacks a separate battery pack and provides direct 12V power.

Overall, the Solar Mio Pro's week on the rugged edge of the Pacific was a success. This solar charger has earned its spot next to the Leatherman, the duct tape, and all the other items I wouldn't escape into the wilderness—or from the zombie horde—without.

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