I’m trying to use rechargeable lithium batteries everywhere I can these days, and I’ve found uses for them in flashlights, motion sensors, radios, portable power sources, wireless keyboards and mice. The trick to using these 4.2-volt batteries in say a 3 or 6 volt application is to make up a dummy battery with a diode connected to the plus and minus ends. The diode provides a voltage drop of just over one volt.
The most common cylindrical lithium battery is the 18500 type, although they can be obtained in AA and AAA sizes.
Using a lithium batteries this way is much better than NiMh batteries as they tend to lose their power over time and their maximum voltage is only about 1.3 volts. I don’t like to use standard alkaline batteries as they often leak and the cost can be rather expensive as well as they have to be recycled. Even though lithium batteries have to be recycled, they last so much longer.
My source of lithium batteries is often the local computer swap meet. I’ve found that I can usually buy a laptop battery pack quite inexpensively, pull it apart and use the batteries individually or combined in some way. Buying batteries this way can be risky, as you could end up with a lot of exhausted batteries. I’ve been fortunate so far in that I’ve managed to extract just over 50% of good batteries this way.
Gerald the Gorilla