It's really a wall charger that can also slowly recharge batteries with the photovoltaic cells. It's nice that this item is a wall charges because you can get a good complete first charge for new NiMh batteries before charging with solar. (It's also good if you are short on time and can charge them from the outlet in much less time than only solar charging.)
The downside to this product is that the batteries take a really long time to charge on solar power alone. There is no meter showing the strength of the current provided by the solar cells and there is no information in the product manual to give any idea as to how long it would take to recharge batteries using solar power only. (Charging from an outlet takes 4-6 hours.)
I estimate that 2 to 3 days of good sun was enough to charge 2 high capacity AAA batteries. (900 mah) Since high capacity AA batteries have a much higher mah of 2300, it would take a very long time to fully charge the four AA batteries with solar power. (I'm guessing over a week) Although a full charge will take a long time, you can always use the solar charger for a partial recharge of your batteries.
The other drawback of this device is that the battery compartment is not enclosed, making the device more vulnerable to moisture. Since you get much more current from the solar cells when they are outside, you have to be really careful about moisture from weather. (You probably want to put the charger in a clear plastic bag.)
Overall I think this is a cool gadget, but if you are looking to charge batteries with solar power alone, other chargers can do the job better.
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