CARE OF CORDLESS PHONE AND CELL PHONE BATTERIES
Tuesday, February 17th, 2009
Proper care of cordless phone and cell phone batteries will greatly enhance their usefulness and longevity to you, the consumer. Some very practical tips regarding these battery types are discussed below.
First, cordless phone batteries found in the home are of two similar but different chemistry…NiCd (nickel cadmium) and NiMh (nickel metal hydride). Cell phone batteries are almost always use the Lithium-ion battery. Here are the advantages and limitations of these chemistries:
Advantages of NiCd Batteries*
- Fast and simple charge, even after prolonged storage.
- High number of charge/discharge cycles - if properly maintained, nickel-cadmium provides over 1000 charge/discharge cycles.
- Good load performance - nickel-cadmium allows recharging at low temperatures.
- Long shelf life - five-year storage is possible. Some priming prior to use will be required.
- Simple storage and transportation - most airfreight companies accept nickel-cadmium without special conditions.
- Good low temperature performance.
- Forgiving if abused - nickel-cadmium is one of the most rugged rechargeable batteries.
- Economically priced - nickel-cadmium is lowest in terms of cost per cycle.
- Available in a wide range of sizes and performance options - most nickel-cadmium cells are cylindrical.
Limitations of NiCd Batteries*
- Relatively low energy density.
- Memory effect - nickel-cadmium must periodically be exercised (discharge/charge) to prevent memory.
- Environmentally unfriendly - nickel-cadmium contains toxic metals. Some countries restrict its use.
- Relatively high self-discharge - needs recharging after storage
Advantages NiMh Batteries*
- 30-40% higher capacity than standard nickel-cadmium. Nickel-metal-hydride has potential for yet higher energy densities.
- Less prone to memory than nickel-cadmium - fewer exercise cycles are required.
- Simple storage and transportation - transport is not subject to regulatory control.
- Environmentally friendly - contains only mild toxins; profitable for recycling.
Limitation of NiMh Batteries*
- Limited service life - the performance starts to deteriorate after 200-300 cycles if repeatedly deeply cycled.
- Relatively short storage of three years. Cool temperature and a partial charge slows aging.
- Limited discharge current - although nickel-metal-hydride is capable of delivering high discharge currents, heavy load reduces the battery’s cycle life.
- More complex charge algorithm needed - nickel-metal-hydride generates more heat during charge and requires slightly longer charge times than nickel-cadmium. Trickle charge settings are critical because the battery cannot absorb overcharge.
- High self-discharge - typically 50% higher than nickel-cadmium.
- Performance degrades if stored at elevated temperatures - nickel-metal-hydride should be stored in a cool place at 40% state-of-charge.
- High maintenance - nickel-metal hydride requires regular full discharge to prevent crystalline formation. nickel-cadmium should be exercised once a month, nickel-metal-hydride once in every 3 months.
Practical tips for using NiCd and NiMh batteries for cordless phone batteries.
- These battery chemistries don’t do well sitting in a charge cradle for long periods of time. They like to be exercised which is another way of saying “cycled up and down”.. Leaving your cordless phone batteries off the charger several times a month will result in extended use. A practical solution would be to leave you cordless phone out of the charger during the day and connected to the charger during the night.
Lithium-ion – Cell Phone Batteries
For many years, nickel-cadmium had been the only suitable battery for portable equipment from wireless communications to mobile computing. Nickel-metal-hydride and lithium-ion emerged in the early 1990s, fighting nose-to-nose to gain customer’s acceptance. Today, lithium-ion is the fastest growing and most promising battery chemistry.
Advantages
- High energy density - potential for yet higher capacities.
- Does not need prolonged priming when new. One regular charge is all that’s needed.
- Relatively low self-discharge - self-discharge is less than half that of nickel-based batteries.
- Low Maintenance - no periodic discharge is needed; there is no memory.
- Specialty cells can provide very high current to applications such as power tools.
Limitations
- Requires protection circuit to maintain voltage and current within safe limits.
- Subject to aging, even if not in use - storage in a cool place at 40% charge reduces the aging effect.
- Transportation restrictions - shipment of larger quantities may be subject to regulatory control. This restriction does not apply to personal carry-on batteries. (See last section)
- Expensive to manufacture - about 40 percent higher in cost than nickel-cadmium.
- Not fully mature - metals and chemicals are changing on a continuing basis.
Practical tips for using lithium-ion batteries for your cell phones
- These batteries shouldn’t be drained or discharged all the way down. Don’t let the last charge bar shown on the phone disappear. This chemistry doesn’t like to be totally discharged.
- Don’t leave your cell phones plugged into car chargers. These chargers seldom are designed to automatically shut off after the battery is charged. Leaving them plugged in all the time will “overcharge” your battery and shorten its life.
- If you have all your cell phone charge indicator bars showing at night, don’t plug them to receive another charge least you run the possibility of “overcharging”.
*Source: batteryuniversity.com