I needed a flashlight, and like so many people, I bought some of those cool LED flashlights. I grabbed one out of my drawer, and the three AAA batteries were dead. I went to buy some AAA alkaline batteries and was shocked when I saw the price. I saw 4 NIMH rechargeable AAA's with a charger,that can be used 500 times and bought that instead.
The cost of ownership of a well maintained rechargeable NIMH AAA is many times less than the throwaway kind, and it reduces the amount of energy required to make the one use batteries and to dispose of the spent ones.
The only thing I did not like about the NIMH was the wall wart charger that will inevitably be forgotten and stay plugged in between the charges, so it becomes part of the background load of the electrical grid.My charger and millions more are just wasting valuable energy.
I looked at my cute 3.2V 85MA solar cells, and decided that a solar charger makes much more sense. The flashlights will run for quite a few hours on a full charge. The 800 MAH duracell NIMH cells can take the 40-85 MA from the panels for many hours and only get slightly warm,and they will be topped off and ready to use when you need it.
A piece of PVC sign board, some hotmelt, A diode for isolation, and some strips of brass and steel, and you have a solar NIMH charger for the three cell battery packs that are used in many of the flashlights. One pack is used while the other sits in a sunny window getting charged with the greenest energy we will ever have.The two panels are put in series with the diode, and the positive and negative solar leads are soldered right to the brass terminals.
No regulator should be required at the
C/10-C/20 rate that the panels max out at.That is only 1/2 watt, which the pack can easily dissipate. I will do some long term test to see how the cells hold up to a several day charge which will hold them at the full charge point.