laptop battery life?

Question

i have an IBM Lenovo T60 thinkpad. Anyway, as this is a common question i dont think it matters.
Its said that the battery life will drop significantly if i always connect the power supply while im working.
So should i just work on the battery alone (i.e. not connecting ac power) OR just connect the ac power and remove the battery ?

So tell me how connecting the power line always will affect my battery

Answer 1

My friend, a retired engineer from Los Alamos, surprised me by saying it is good for the batteries (though he didn't say any effect on battery stamina) to unplug them on a regular basis and let them run down to near "empty", then plug them back in and recharge them. Exercise, he called it.

Answer 2

Battery research is focusing heavily on lithium chemistries, so much so that one could presume that all portable devices will be powered with lithium-ion batteries in the future. In many ways, lithium-ion is superior to nickel and lead-based chemistries and the applications for lithium-ion batteries are growing as a result.

Lithium-ion has not yet fully matured and is being improved continuously. New metal and chemical combinations are being tried every six months to increase energy density and prolong service life. The improvements in longevity after each change will not be known for a few years.

A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.

Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate. (Read more in 'Choosing the right battery for portable computing', Part Two.)

Aging of lithium-ion is an issue that is often ignored. A lithium-ion battery in use typically lasts between 2-3 years. The capacity loss manifests itself in increased internal resistance caused by oxidation. Eventually, the cell resistance reaches a point where the pack can no longer deliver the stored energy although the battery may still have ample charge. For this reason, an aged battery can be kept longer in applications that draw low current as opposed to a function that demands heavy loads. Increasing internal resistance with cycle life and age is typical for cobalt-based lithium-ion, a system that is used for cell phones, cameras and laptops because of high energy density. The lower energy dense manganese-based lithium-ion, also known as spinel, maintains the internal resistance through its life but loses capacity due to chemical decompositions. Spinel is primarily used for power tools.

The speed by which lithium-ion ages is governed by temperature and state-of-charge. Figure 1 illustrates the capacity loss as a function of these two parameters.

Answer 3

If you continuously charge the battery without using the battery it will eventually become immune to being charged. There is nothing wrong with working with the laptop plugged in and having the battery charged if you frequently use the battery. The manufacturer recommends letting the battery drain one in a while so you can charge it back the whole way.
Just from experience, these batteries typically don't last much longer than one year. This is why most laptop warranties don't cover the battery for more than one year even though the laptop may have a 3-year warranty.