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Save Wireless Phone Batteries Money and the Environment

OddMix.com - Power Technical Note - PWRN0704 - by Karl Nagy

Pict. 1. Different Three Cell Wireless Phone Batteries [9 KB]
Picture 1. Different Three Cell Wireless Phone Batteries

Wireless telephones are seemingly everywhere nowadays as they make life easier around the house. No unnecessary wiring is required and - hopefully - they are readily available to use when needed. Furthermore, wireless telephones are often available on occasions of special sale promotions and with rebates for as little as five dollars. At first these wonderful communications devices take on their responsibility with great gusto. Usually no malfunction is in evidence until about the unit becomes one year old.

And the trouble with these wireless phones are always begins with their batteries. Radio telephones are almost invariably powered by a three-cell battery arrangement as in Picture 1, usually in the form of Ni-MH (Nickel Metal Hydride) or in older phones the Ni-Cd (Nickel Cadmium) batteries. These two battery types, as far as the telephone see them, are functionally identical. Their voltage is almost identical; usually they differ only in their capacity (even that can be matched without much difficulty) - and of course in their price. Ni-MH batteries are preferable to the older Ni-Cd types as they have higher capacity and they are free from the Ni-Cd typical and troublesome nemesis the - memory effect.

However even the current state-of-the-art Ni-MH batteries in Picture 2 are not immune to abuse. And, since phone makers are make much more money on the replacement batteries, they are not terrible verbose when it comes to prevent battery failures much before it has to happen. Almost no wireless phone maker instructs their customers for the proper care of the batteries included inside their telephones even so they are essential for the phones trouble free operation.

For starters - a Ni-MH battery (or even a Ni-CD) is capable to serve about 500 full charge-discharge cycles. These type of service is very rare as most batteries only experience partial cycles. The less deep are these partial cycles, the more of them can a battery perform. And the service life ratio is not linear. A typical battery pack can do 2,000-5,000 half cycles without much exertion. Since almost all of us replace the phone on the charger when the call is over, the charging rapidly replaces the little electricity used up of the battery during the call. That should be good, if it would not be going on continuously for years on end. But, because it is so convenient to just return the phone to its base, that is precisely almost always what happens. And millions of overcharged telephone batteries continue to receive more and more charge endlessly.

Pict. 2. Three Button Cell Wireless Phone Battery [9 KB]
Picture 2. Three Button Cell Wireless Phone Battery

Of course this energy used for the unnecessary overcharge is not very large in itself, but multiplied by tens of million times it represents a sizeable amount of wasted energy. And it also represents unnecessarily wasted millions of batteries buried in garbage dumps as well. And because the American Dream for many is such that ripping off the public when they can't avoid the bill, they are too happy to sell a replacement battery for a wireless phone for more than the price of the telephone was initially. A ten, fifteen dollars price for a phone battery (payable on average once a year) is as common nowadays as a $30 USB cable. In more civilized countries that kind of predatory pricing is a crime.

Happily all of this expense can be easily avoided, by not always placing the telephone onto its base. It may take a little while to get use to it, but by and large, if a phone was used for a few hours during the day, then leave it on the base for a few hours. A fully discharged battery pack recharges in 14-16 hours - the exact time very much dependent on the charger itself. The number of hours depends on the battery capacity and the charge current. This information is usually written on the battery or it may be (should be) in the telephone User's Manual. Shorter use times may warrant charging on every other day.

Do NOT drain the last possible milli-amperes out of the battery pack however, as that can be very damaging to the assembly. Many newer phones continuously monitors battery voltage and prevent over discharging of it's battery pack. If in doubt, do NOT over-discharge. Just operate the phone's battery on the high end of its capacity (charge cycle) and the original battery pack will easily last many years. It is not unreasonable to expect that it will last out the life of the original telephone.


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