Most electronic devices such as cell phones, PDAs, and digital cameras use one or more rechargeable batteries to supply the unit with power. The benefits of rechargeable batteries are clear. You don't have to replace the battery when it is out of power, saving the expense of new batteries over the long-term.

However, not all rechargeable batteries are the same. Knowing the kind of battery and how you're supposed to use it over the life of the battery can significantly increase its overall life and performance. 

Different Kinds of Rechargeable Batteries

The common types of rechargeable batteries are Ni-Cd, Ni-MH, and Li-ion. To find out what kind of battery your device uses, look for a sticker somewhere on the battery. 

Nickel Cadmium (Ni-Cd)


Nickel Cadmium batteries are the most common, and least expensive kind of rechargeable battery. Ni-Cd batteries have been around for more than 50 years. Ni-Cd batteries work well in high current drain devices like portable radios and motorized devices.

Ni-Cd batteries are subject to a phenomenon known as "memory", which means that the battery will adapt to carry the capacity most commonly used. The memory effect is very common in cordless phones. Often, cordless phone owners usually always place a phone back on the charging cradle after finishing a phone call. So, a cordless phone user usually never uses all of the charge remaining prior to recharging the phone. Over time, the battery will slowly reduce its capacity to match how much of a charge is normally used. After much of this, the battery's possible charge capacity could be a fraction of what it once was.

To ensure you get the most life out of a Ni-Cd battery: 

• Use the device until the battery is completely exhausted at least once a month before recharging. This will ensure that the battery always can charge to its full capacity each and every time.
• Always allow the battery to fully charge without interruption, especially the first time. Frequent interruptions during the charging cycle can cause the memory to build faster.
• Fully charge the battery prior to storage.
• Do not leave the battery on the charger for more than two days.
  

If used properly, Ni-Cd is a durable battery that can be cycled more times than any other rechargeable type. However, since the battery contains toxic metals, be sure to recycle it at the end of its life. 

Nickel Metal-Hydride (Ni-MH)


Nickel Metal-Hydride batteries are another common rechargeable battery type, and have been in service since the mid 1980's. The amount of power held in this kind of battery can be roughly two to three times higher than Ni-Cd

batteries. Ni-MH batteries have a significant advantage over Ni-Cd batteries because they don't suffer as much from a memory effect, unless they are charged at an extremely slow rate or not cycled occasionally. This means that Ni-MH batteries can be recharged at just about any time, without loss of overall capacity. Most Ni-MH batteries can be recharged 500 to 1000 times before the end of the battery's life. To ensure the best performance using Ni-MH batteries: 
• Be sure to use a charger specifically designed to charge them. Ni-MH is charged differently than Ni-Cd batteries. Using a charger for only Ni-Cd batteries will ruin the battery.
• Do not charge Ni-MH batteries in an extremely cold or hot environment since it can damage the battery.
• Overcharging a Ni-MH battery can significantly reduce its useable life.
• To maintain the battery, try to use at least 80% of capacity prior to recharge every three months.
• Do not slowly charge a Ni-MH battery which can cause a memory effect to occur.
• Do not leave a Ni-MH battery on a charger for more than two days.
  

Lithium Ion (Li-ion)


Lithium Ion batteries are intended for use in high current drain devices like laptops and cell phones. Lithium batteries can hold more power than any other rechargeable type. They also do not have a memory effect, so frequent discharges are not required.

However, Li-ion batteries do have their downside. Lithium batteries wear with age, so the expected service life is based mostly on age instead of cycles. As the battery gets older, the overall capacity will diminish whether you use it or not. Lithium batteries react to recharge cycles differently than nickel based batteries, so you should avoid completely discharging a Lithium battery.

There is not a lot you can do to ensure a longer life with a Lithium battery, considering they wear with age rather than use. However, you can ensure the best performance while operational by: 

• Keeping the battery charged rather than let it lose its charge.
• Keeping the battery cool, so don't store the battery in a hot car or near a heat source.
• Charging the battery to around 40% for long term storage.
• Avoiding full recharges, when possible.
• Batteries with a fuel guage should be allowed to completely discharge every month to reset the guage. If not, the fuel guage will become less accurate over time.
  

Proper use and care of your rechargeable batteries not only gives you better performance, but can also extend the life of your batteries. Remember, many rechargeable batteries use toxic materials, so be kind to nature and dispose or recylce them properly when they are no longer usable.