Personally I think its a bad combination....
the flashlight is still a flashlight [batteries, etc] only with a solar panel
LED = moderate voltage / low amperage
Batteries = [depending on type] output: high voltage, high amperage / input [charging requirements] Constand current, high voltage
Solar panel [PV] = high voltage / low amperage
In order to effectively charge the cells [ideal advantage] there would be a large area covered with the PV cells and ideal charging would require the specs set at one sun conditions throughout the charging process.
Since the batteries will require a stable current, there might be a resistor in there witch will lower the efficiency of the cells...
Correct me on this....if i needed a correction
From flashlightreviews.com, the solar flashlights dont convince me as an Ideal illumination / survival tool....
If you dont want to use batteries....
then buy
this
Info
Brochure .pdf