Solar power chargers are steadily beginning to occupy the shelves of most retailers. While that doesn't mean classical recharger units are gone, it is still a proof that more and more people are using these devices and they are becoming aware of the fact that trying to save the planet is a must.
And even if that wasn't their purpose, they would still have a lot to gain over solar chargers. Thus, solar powered chargers can work continuously as long as the sun is shinning, while the energy being produced is "clean" and doesn't cost anything.
Recently, solar chargers have started to penetrate some non-standard market segments. While at their beginnings, solar charging units were specifically designed to charge standard batteries, now you can get several not-standard chargers capable of loading some of the weirdest batteries that ever existed.
Take the SolarAid BTE Hearing Aid Battery Recharger produced by Godisa and presented since the first half of 2007 for example. If you get past the intricate naming (and you have to, since it is a bit too long) this is a classical recharger making good use of solar power. However, besides the AA batteries, it can also work with several non-standard batteries used mainly to power up hearing devices.
According to the manufacturer, the device can charge two AA batteries and 2 size 675 or size 13 button cell rechargeable batteries simultaneously. That's pretty good performance, but actually it's not the wattage that matters. The fact that it's weather resistant and can recharge a lot of hearing devices gives it the upper hand since there aren't many rechargers capable of doing that.
Unfortunately the producer doesn't say anything about the price or availability so buying this device will be almost impossible unless you're living in Botswana, where Godisa has an operational center.