Rechargeable Notebook Batteries - Shelf
Life and Notebook Battery Maintenance
Tips
Lithium Ion notebook batteries wear down because of two factors: 1) active usage in your
notebook battery and 2) natural aging of the notebook battery. Both will wear down your
notebook battery over time; the trick is to minimize their impact while still getting the
performance out of your laptop battery that you need.
The most important thing to understand about laptop batteries is that they are always
losing a small bit of their charge. The hotter the temperature, the faster notebook batteries
loose their charge. So rule number one is: keep your notebook battery cool. Notebook
battery manufacturers store their products at around 60�F. (It doesn't help to put them in
the refrigerator, and you can damage a battery by freezing it.)
The second most important thing to understand about notebook batteries is that their
capacity decreases with each cycle of charging and discharging (or usage). By itself, this
is not surprising - but when combined with the previous point, it leads to a surprising
conclusion.
When laptop users leave their laptop battery inside the machine but leave the computer
plugged into the wall, the laptop battery is going through a constant charge-discharge
cycle. The notebook battery is sitting unused inside the notebook, discharging a little
faster than normal because of the notebook's heat. Once its charge level drops to a
predetermined level (which is different for each manufacturer), the AC adapter provides
extra juice to "top off" the notebook battery. As the laptop battery gets older, it tends to
self-discharge a little faster, which accelerates the process even further.
Lithium ion notebook batteries normally offer 600 to 800 charge/discharge cycles over
1� to 3 years of useful life. When you use your notebook battery as described above,
you are needlessly using your supply of recharges.
One additional note: many people recall that older notebook batteries on early computers
worked best when they were fully discharged before being recharged. While that remains
true for Nickel Cadmium technology, today's Lithium Ion notebook batteries work best
when they are recharged when they still have 10 to 20% capacity remaining. So if you are
using your notebook battery on a long flight, try not to get in the habit of using the
notebook battery until it has almost no charge. Your laptop battery literally won't be the
same when you re-charge it the next time.
Some Guidelines for Notebook Batteries:
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Remember that new laptop batteries generally arrive in a discharged state; you
must charge them up for at least four hours before their first use.
Keep your laptop battery cool, but do not put it in the refrigerator or freezer
Don't use the notebook battery if you don't have to! Many people keep their
laptop plugged in most of the time. They can preserve their notebook battery life
by storing the battery outside the laptop in a cool place.
Try to avoid running your laptop battery all the way to zero
Don't charge your notebook battery before long periods of inactivity
Much as we'd like to sell you more laptop batteries, don't buy spare notebook
batteries for later use. The longer you hold them, the less useful life they provide
Laptop Batteries - Charging Lithium Ion
Laptop Computer Batteries
Charging laptop computer batteries used to be easy in the good old days of Nickel
Cadmium technology and lead acid cells. All you had to do was build a circuit that would
adjust the voltage in such a way that the charging current did not exceed 50% of the
laptop battery's milliAmp hour (mAh) capacity. A couple of hours later and presto - you
had a charged laptop computer battery. A few milliAmps above or below the maximum
capacity were easily tolerated, with only a slight degradation in the overall life of laptop
computer batteries.
Today, Lithium Ion laptop computer batteries are the most advanced technology in terms
of energy generated per pound. These laptop computer batteries are unfortunately very
unforgiving, when it comes to charging. The charging current and voltage must follow
very strict curves over the 180 minutes recommended for a full charging cycle. Lithium
Ion laptop computer batteries will not tolerate lower levels of current like the car battery
can when it is close to full charge. Instead, laptop computer batteries require a special
circuit that will control that current and limit it as the laptop batteries approach a fully
charged state.
For this reason, all laptop computer batteries are equipped with a rather sophisticated
charging circuit inside the laptop battery that regulates the charge and discharge current
and also communicates with the computer about remaining capacity. This communication
occurs over a specific data bus that is tied to power management software installed on
every system. (Many users are familiar with the related Control Panel application that
estimates remaining battery life and controls settings that minimize power consumption.)
This same charging circuit has a temperature protection feature that ensures the laptop
battery doesn't over-charge and over-heat. Some laptop computer batteries achieve this
functionality via a thermal fuse that opens when the temperature exceeds 50-60 degrees
Celsius. Other laptop battery designs use a thermistor (thermal sensitive resistor) that
communicates the laptop battery temperature at all times to the charging circuit and stops
the charging process in case of overheating. Temperature management is so important in
Lithium Ion laptop computer batteries
that the newest laptop battery designs employ both methods and components.
An interesting fact regarding laptop computer batteries is that most of the laptop battery's
charging takes place in the first 80 minutes of charging. This is the case in laptop
computer batteries, despite the fact that a full charge takes generally 180 minutes. This is
a little known fact that can save us time while waiting for that well-known amber light to
turn into green. The graph above illustrates this fact. Notice how the battery's charge (on
the Y axis) levels of dramatically after an initial period of time (X axis).
Please note! Despite this graph, new laptop computer batteries should be fully charged
for at least the first three or four cycles to ensure that the laptop battery is properly
"broken in".