For instance, if you want a durable battery with a long life, you won't be able to find something tiny and cheap. On the other hand, you might be able to find a small battery that can be used an extended life and supports continuous use, but it won't last forever. Here is a look at the pros and cons of what's available.

- Nickel-Cadmium - Nickel-Cadmium batteries have long life and high energy outputs. They can withstand extremes in temperature quite well. They have been the industry standard for a long time for things such as radios, medical equipment and power tools, but in recent years, Nickel Metal Hydrite types are preferred. One reason for this is that the cadmium in Nickel Cadmium is highly toxic. Another reason is that Nickel Cadmium batteries sometimes have what's called the "memory effect." Basically, when they are recharged, if they are not fully recharged correctly, they will wear themselves out quickly again and be worthless. Still, Nickel Cadmium batteries are high performance disposable power cells.

- Nickel-Metal Hydrite - These batteries make some improvements on the old Nickel Cadmium variety, and that is why they are replacing them as an industry standard, appearing most recently in laptop computers and cell phones. They do not have as long a life and are not rechargeable, but they have a higher energy output and are made entirely from non-toxic materials. They are also usually cheaper than Nickel Cadmium version, depending on the brand. These are the most recommended batteries for just about everything, with the exception of certain emergency devices which require a battery that has a longer life.

- Lithium Ion - These batteries are great for any kind of portable device because they have the same energy output and capacity as Nickel Cadmium and Nickel-Metal Hydrite power cells. Unlike the previous two, Lithium Ions are small and light. This can make a huge difference, especially with small portable electronics. The only problem with Lithium Ion batteries is that, although not toxic, they are flammable. This means that some care must be taken in the design of the device they are used in, and that they need to be disposed of carefully. Lithium Ion power cells are the fastest growing in the industry, and improvements are constantly being made. This appears to be the battery of the future.

To simplify a little, let's look at which types work best for which devices...

Zinc carbon/ zinc chloride - Clocks, small lights and toys.

Alkaline - Flashlights, small radios, bigger toys, cameras.

Silver oxide - Small calculators, cameras.

Zinc air - Pagers, hearing aids.

Nickel Cadmium - Power tools, heavy duty equipment, emergency lights.

Nickel-Metal Hydrite - Laptops, cell phones, hand-held video recorders.

Lithium Ion - same as Nickel-Metal Hydrite.

One more type of battery that should be mentioned is the "smart battery." A smart battery can be any kind of battery, but what makes it "smart" is the fact that it communicates with the electronic device to monitor its own performance and adjust accordingly. These are often used in laptops, medical equipment, and high-end portable electronic devices.

The world of batteries is complex and highly technical, but hopefully this short introduction will give you some ideas about which battery is best for your application.