Battery Guide Rechargeable Batteries River2u.com
Types of Batteries
Ordinary batteries produce energy from a chemical reaction. Rechargeable batteries work on the same principle, but unlike ordinary batteries, the chemical reaction can be run in both directions so that they can repeatedly store electrical energy during charging and deliver it while discharging. Not all rechargeable batteries are alike, however, so when shopping for a rechargeable battery, consider these common alternatives:
  • Nickel cadmium (NiCad) batteries were the first rechargeable batteries. They come in all of the common sizes of ordinary batteries and have the lowest purchase price. Generally, you may charge and discharge a NiCad battery hundreds or even thousands of times, but these batteries have a tendency if not fully discharged to become unable to hold their original charge. The partially depleted capacity becomes their full capacity in a phenomenon known as memory, but they can recover if fully discharged and recharged a couple of times. They tend to lose power even when not in use and so fully discharge in a month or so, depending on the battery. Nevertheless, the total cost of ownership for NiCad batteries can be dramatically lower than ordinary batteries for demanding applications like digital cameras.
  • Nickel metal hydride (NiMH) batteries do not suffer the memory problems of nickel cadmium and are generally lighter for the same amount of power. Like NiCad, NiMH batteries come in all of the standard sizes and have a similar, though improved, shortcoming in shelf life. NiMH batteries may not be a suitable substitute for NiCad in high drain products like power tools, but in every other application, they will generally perform better at a somewhat higher price.
  • Lithium ion batteries improve upon nickel metal hydride with even more power in a lighter package and will hold their charge for months without appreciable loss. Lithium ion batteries power top of the line notebook personal computers. Their current disadvantages are their higher price and their limited use (they are not available in ordinary sizes because of the complexities that require that they be recharged in specially designed chargers).
No matter which technology you choose, a rechargeable battery eventually loses its ability to take and then deliver a full charge. Once the capacity begins falling significantly, it is time to replace it.

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