The following article is not complete, only I don't have time to finish it properly. However there may be useful information in it, in the present form, so publish it. I may finish it someday...

When I first saw it I knew that I will have one. During our usual summer trips one of the bost severe problem is providing power for our elecronic devices. As we usually sleep in forests or wherever we stop, charging is impossible. During the day we rarely stop at inhabited places, so asking someone to charge the devices is out of question too. What we can do is carry a lot of (rechargable) batteries, what is a lot of plus weigth that we do not want to carry.
Then I saw this charger, and bougth it almost immediately. The nominal charging current is 150 mA for a pair of batteries. That is quite impressing for a lightweigth device like this. Most of the NiMH/NiCd battery chargers do not have an output higher than 200-250 mA.
This means that a pair of 850 mAh batteries (like those bundled with the charger, type AAA) can be recharged in less then 8 hours. (the usual formula for this calculation is 1.4*Capacity/Charge current, 1.4*850mAh/150mA=7.93 h for the aforementioned batteries). That usually means a sunny day's most intensive hours.
Surprisingly after some measurements the charging current proved to be more than stated, and reached 165 mA. Not a big gain, but at least we are not cheated by the marketing department. Of course thes currents apply to optimal conditions: direct sunshine, sun is high on ?zenith?, the plane of the solar panelis ?perpendicular? to the incoming rays. In cloudy weather or with the sun near the horizon the current decreases or even stops charging.
Near the batteryes a LED indicates charging, the brighter it is, the more current flows.
And this is the end of the list of the features. Or there is one more I have to mentio: this year I saw one that had an AC adapter bundled,which is a good idea regarding you don't have to carry another charger for the cloudy days. Not a complicated device, no sophisticated charging methods (it may be a problem, see later). The advantage is its weigth. It weighs only a few gramms. And it is durable! My 20+ kg backpack accidentally fell on it, and bent the panel. As the panel is a flexible thin plastic with 3 stripes of ?policrystalline? solar panels it suffered some damage, but not in its function. It is still working as it should.

For me this charger has been a blessing, it helped me to make thousands of photos. I could fit it on my backpack easily with a piece of rope. Always facing the sun.

Are there disadvantages? Of course there are. Let's start with the one concerning the batteries lifetime.
Preferred charging method of NiMH/NiCd batteries is using constant current. With solar power only one thing is sure: you probably won't have enough sunshine hour providing constant current. There may be clouds, or simply you need more days to fully charge a high capacity battery. In this case you violently brake the law of charging. Early batteries had the so called "memory effect" which caused premature decrease in capacity. If your battery is of this kind, you can kill them in to time using the solar charger. Luckily these days the batteries have no memory effect, especially the most recent types (slowly self-discharging, but lower capacity,a.k.a. Ready2use,etc.) At least the batteries I used have not been damaged.
The other issue is the end of the charging. Advanced chargers monitor while charging, and terminate when the battery is full (usually deltaV method, voltage reaches a maximum, then starts decreasing). Using simple chargers the user has to terminate after the desired period.
It is not possible to determine the charge with this charger. The voltage is not measured, the current is not constant,thus the required time is unknown. The most safe method is using two pairs of batteries (which surely don't have memory effect), and change them regularly. The changing period  should be chosen shorter than the time needed for fully charging under optimal conditions. This prevents overcharging and wasting the precious electricity.

The last disadvantage is in connection with the material of the charger. The panel is soft as said before, which is not advantageous in every consideration. It gets scratched easily which means, the surface transparency decreases, and fewer photons can reach the useful parts.

The last questionable property applies to all of the compact solar chargers: the heat. The sunshine will generate a lot of heat on the chargers, and the objects around. Naturally that will cause the battery's temperature to rise. And batteries of everyday's usage are sensitive to heat in general. Li based batteries the most, but NiMH-s also.

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