Top positive review
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More realistic than integrated units if you live in the UK
on 1 June 2013
**BE AWARE** This device has no voltage regulator and can produce over 6 volts in bright sunlight. If you find your device will not charge it may be due to the device protecting itself from possible damage. See edit 1 at the bottom for more detail.
I bought this for two reasons. Firstly to recharge the battery bank I already own (different manufacturer). I live in the north of England so most integrated solar chargers simply aren't going to cut it due to the small size of their solar panels. Larger panels don't just generate more power, hopefully they will make more of the limited sun light available here. Secondly I wanted to be able to directly charge my devices as this is more efficient. When using the battery bank I'm only getting about 40% transfer efficiency. In other words the 5600mAh unit only charges my 1460mAh phone battery about one and a half times, equivalent to around 2200mAh. It's obviously therefore a lot better to directly charge your devices as it takes two and a half times as long to do so via an intermediate battery.
I have 5 devices which I tested on the 31st of May 2013, the hottest day of the year so far (17 degrees C!) with generally clear skies. Here are my findings:
Nook Simple Touch eReader. This works really well and will charge even with hazy sunlight. It charges at about mains charger speed.
Sony Xperia Miro. My main phone. This proved temperamental and would only start to charge with strong direct sunlight. It still managed to charge from 68% to 95% in around an hour so it will be viable if you are planning a trip to more sunny climbs. I was unable to get it to charge after about 5pm even though the sun was strong enough to make the panel quite warm to the touch. See edit 1 below for follow up comments.
Nokia N96. This entered charging mode more readily than the Sony. I couldn't really tell how fast it was charging though, as the battery indicator doesn't give a percentage reading.
Apple iPod Nano (5th gen). This wouldn't charge even when there was enough light to charge the Miro. This may not bode well for iPhone users.
Battery Bank. This readily enters charging mode even with fairly modest light. As a test, I fully charged it from the mains before using it to charge my Miro by about 10%. I then used the solar panel to recharge it. This took over an hour but it finally got back to fully charged (all indicator lights on constantly).
Edit 1: I have been experimenting with charging my Miro phone as this is the most important device for me. I eventually discovered that partially covering the panel would cause the Miro to start charging. I checked the output using a meter and found that it was producing 6.06 volts rather than the normal 5 volts you get from a USB port. This must have been tripping the phone's over voltage protection. As an experiment I connected a cheap (under £5) solar charger I had bought on eBay some time ago (which has a dud battery) in series with the panel. The panel connected to the charging port and the output connected to the phone. It has a built in VOLTAGE REGULATOR that stops over loading the phones input. It worked like a charm and will now charge my phone under a wide range of lighting. As these things cost a few pennies, I've knocked a star off my rating because of this omission.
Edit 2: Just a follow up to my original review. I was able to power my Miro phone entirely on solar power for over 4 months last summer, June - October. The second week in October finally forced me to revert to mains charging. A full charge takes 3-4 hours on a sunny day. The longer times were later in the year when the sun being lower in the sky has lower ultraviolet content. I eventually started to use my battery bank in "pass through" mode. This allows it to act as a regulator to the solar panel, prioritizing the phone and only charging itself once the phone is fully charged. Not all battery banks can operate like this, so check before you buy.