The first generation of rechargeable devices plugged directly into a wall outlet. More recent rechargeable devices are made to plug into a computer's USB port, and has already been adapted to the smaller micro USB ports.

Manufacturers have moved into this market in a big way, and online sources are already full of fast, portable 12 volt chargers capable of charging double-AA and triple-AAA batteries. Some 12v units can charge up to 4 batteries at a time and deliver a rapid charge in two or three hours.

However, this was only the beginning. As we seek alternative sources of cheap energy, attention is turning to the sun. Early issues with solar powered chargers have now been largely resolved, making them smart choices for small applications.

Solar AA Battery Charger

One solar cell can only generate a small amount of electricity, but this has been addressed by using multiple cells to generate electricity for a fast charge. A solar panel can be linked to others in configurations ranging from smaller arrays of 6, 8 and 10 panels up to much larger groupings.

Another objection to solar power is that when the sun is gone, so is the power. The answer is to use the sun to charge a battery, then use this as a charger for other things. To fill this need, a generation of quick, rechargeable batteries has emerged.

Old-style alkaline cells seemed adequate in a less environmentally conscious time, but have fallen into disfavor because they contain potassium hydroxide, a hazardous chemical that leaks over time. While alkaline AA and AAA batteries are still widely used, alternatives are emerging.

The lead-acid cell is used for car applications, but has a poor environmental record and low energy-to-weight ratio. However, even this kind of cell can benefit from new technology, and many auto owners now have an emergency travel charger in the car to give their battery a jump. For those who don't mind the exertion, there's always the hand crank charger.

The lithium ion battery or LIB works by the movement of lithium ions between positive and negative electrodes. Overcharging can damage an LIB and decrease its storage capacity, a problem addressed by intelligent systems that stop charging when the cell reaches its limit. Some systems are programmable and universal, i.e. capable of charging all battery types.

Industry first gave us nickel-cadmium (NiCd) cells, then nickel-metal hydride cells. The latter, known as Ni-Mh cells, can double or triple the capacity of NiCd cells. Early NiMh cells sometimes lost large amounts of power even when not in use, an issue eliminated by the introduction of low self-discharge NiMh batteries.