Deciding whether a solar charger is going to be enough to keep your IT going without the backup of a wall socket or USB port is about as tricky as predicting the weather, in fact both are inextricably linked. Harder still is finding a solar charger at a low weight that stands a chance of keeping the power flowing to your devices.
We’ve used very small charging devices on treks in the past and the performance is often much poorer that you expect – so were reporting here on how one mid range, mid weight product performed on the Tour of Mont Blanc.
What we know about solar chargers..
We know that you can get a large solar panel that will directly charge your device when exposed to full sunlight, but these are heavy and only work in full sun.
Solar chargers at a more reasonable weight for a backpacker generally come with two components parts to the unit, there’s a battery and a solar panel. The solar panel trickle charges the battery because it doesn’t develop enough power to charge your device (such as a phone) directly.
After many hours trickle charging the battery can then be used to charge your phone – or whatever. For the rest of this article I’m going to say ‘phone’ – but that could mean any device.
The advantage of the battery/solar panel combination is that you can charge the battery up from the mains before you go away. That means you have access to power whether the sun shines or not. In the case of the Freeloader ISIS you have two full charges of your phone before the battery runs out – we tested this and you’ll see from the data below, that it seems accurate.
Immediate likes about this product were the respectably low weight and two full charges available to me even without the reliance on solar power. I also liked the rubber holder which has a ‘belt loop’ so you can attach it to various straps on your rucksack. The unit has a USB output but also has two phone plugs, a Samsung-esque D plug and an Iphone phone plug, handily permanently attached to the unit. My camera also uses the Samsung plug – which would allow me to charge the camera also, should that be necessary.
CAMERA – just a point though, the most weight effective way I have found of keeping my camera charged on a long trek is to pack an extra battery – fully charged. The spare battery for my Sony RX100 weighs 21grams and it takes the pressure off my solar charger. Over two weeks I took 380 photographs, reviewed them at the end of most days and I didn’t have to change the battery until day 12.
Back to the Freeloader ISIS; the main purpose of which was to keep my phone going. I have a Samsung A3 and my pal has an IPhone 5s. The first tip is to turn it off when you’re not using it! Sounds obvious but I’ve eeked a single charge out for a fortnight with this technique and infrequent use.
The first time we used the ISIS was on day three to re-charge our phones. The Samsung was on 60% and the Iphone was on 55%. We brought them both to 95% in about 90 minutes. Second Tip; stop the charging before 100% because once the phone is fully charged the battery will continue to discharge into it for little benefit.
A few days later the ISIS unit re-charged our phones from around 55% to 92% in just over an hour. It was still charging but we stopped it and decided to try to re-charge the battery from sunlight the next day. Our conclusion so far was that you could indeed get two full charges from a fully charged battery – as Freeloader claim.
Solar Charging Cycle
The ISIS unit has a display to indicate its state of charge – there are four ‘blocks’, at the beginning of this test there was one block displayed. The very first day was beautiful and clear – full sun – the ISIS unit was mounted to the pack face up to the sun – perfect charging conditions. After eight hours the display showed two blocks.
The next day was a mixture – a lot of walking in woods, some cloud, only 6 hours – still only two blocks.
Next day was full sun for about 7 hours – got up to three blocks by the end of the day.
Next day was cloudy – didn’t move beyond three blocks. Needed to charge Samsung phone – charged from 40% to 96% - display showing a single block again.
Next day full sun but didn’t get above one block. Next day lots of walking in woods, charger now the wrong side of pack for full sun, but got to 2 blocks. Next day very mixed, cloudy most of the day. Still on 2 blocks by the end of the day.
Charged Samsung from 16% to 70%.
ConclusionIn full sun you can probably rely on half a charge per day for your phone, but this is drastically reduced if there’s no sun, you’re walking in woods or the unit isn’t ‘face to the sun’ all the time because you’re walking