Whenever I’m traveling, particularly outside the US, I have range anxiety on my cellphone. Not only is it my communications (and my important poster-of-pictures-of-food-and-cocktails), it’s more importantly my navigation and often the way I summon transportation. In some countries, I can ask my way using schoolboy French or German, but my travels necessarily direct me to Romania on occasion – and I speak none of that (yet – yes, I know, I should learn it). There are a LOT of fake-advertised-capacity battery packs on eBay and Amazon, but I’ve used the KMashi 15000mAh battery packs and love them – they typically last me 15 months or so, and they’re sturdy, reliable and seem to match their advertised capacity pretty closely.
However, even the best battery pack isn’t an all day charge extravaganza, and I often leave my hotel early and walk around all day and well into the evening. Also, when I’m in places like Puerto Rico, I spend a goodly amount of time on the beach, where a solar charger would seem to be ideal to charge my media player and external speaker, if nothing else. While there are a lot of “solar charging USB power banks” on eBay, they all have tiny solar panels because they’re pocket sized – and most of the ones I’ve seen reviewed were terrible misadvertised shanzai products that didn’t even come close to their rated battery capacity. (Here’s one good review of a few – there are a bunch of other videos on YouTube of more or less professionalism). Even if they’re advertised honestly, however, these are really just for emergency situations like “I’m camping in the woods and my phone is dead and this is the only power source I have and I can afford to wait a whole day in order to make one emergency phone call”.
Thus, I recently purchased this “10W” solar charger, mainly for experimental purposes. It has two nominally 2A USB type-A receptacles, and it folds up nicely into a paperback-sized package. For $20, it wasn’t much of an investment – and I can say that it actually works pretty well. In late afternoon direct sun, it delivered about 350mA which is unexciting, but in intermittently overcast conditions around midday, it delivered close to 1A (980mA or so) to the old iPhone 4S I use as a media player. This is enough to charge the phone about 25% over the course of a lunch hour. It occurs to me that in fact the iPhone 4S shipped with a 1A charge adapter, so the phone itself may never want to draw more than this amount, but honestly at the price, I was expecting not even to get close to 5W. I did however learn two things about these solar chargers. These discoveries are a little non-obvious and I haven’t seen them mentioned much, if at all, in other reviews.
The first note is that phones and similar devices are designed to be charged by a wall adapter of fixed current delivery capability and fairly restricted output voltage range. That adapter will output something close-ish to 5V for all of its rated current range, and then either go into shutdown or significantly drop its output voltage if the current capacity is exceeded. Particularly if there are clouds or other intermittent solar obstructions, solar chargers don’t work like this. So you may find that your phone negotiates what it believes to be a safe charging current when the panel is fully insolated, but if a shadow falls across it the panel’s output will sag and the phone will stop charging – depending on the phone’s software, it may or may not resume charging, or it may drop to a lower charge current setting and stick there even once the solar panel gets back to full power. This behavior can be sort of sidestepped by using the panel to charge a (less smart) external battery pack, and then using the pack to charge your phone, though of course you incur more efficiency losses there.
The second note is that many of these panels have what looks like a clear vinyl cover over the solar array. It remains to be seen how long this layer will stand up to so much direct sunlight. I expect both yellowing and brittleness to be a problem, likely within fairly short order. This is something I won’t have actual data on for a while, but it’s something to consider – the lifespan of this item, if used frequently, could easily be a year or less.
Overall however this does seem like a worthy travel companion – it’s light, and it gives you “free” energy. Particularly for charging smaller items like watches, GPSes and rechargeable flashlights (maybe camera batteries too), it is well worth the small monetary outlay.