Now that nowadays, there are many notebooks are sold than desktops, I think it's important to learn about how to care the battery in the laptops, if you intend to use it for a long time.
I like to share my own experience with laptop batteries.
With proper care, a battery can last very long and hold almost the same capacity over the time (but of course the maximum charge will always get less and less, it's normal, as it comes from the battery life cycle - the more you use it, the more it will get worn out).
If you don't use the battery, it will also get damaged, but more about that later.
My laptop's battery still have almost the same capacity as I bought it:
In 2008, it's factory capacity was 48400 mWh
Today, in 2012 it's capacity is 44400 mWh
(AIDA64 says it's 8% worn, and a few months ago it was still about 46000 mWh)
Of course it depends on each and every battery, that how long it will last, for example I saw a brand new laptop's battery is already worn out to 10%
So even if you make everything to care the battery well, but it still worn out very fast, that means it was faulty.
Here are my tips to prolong battery life:
1. Don't use the battery every time, it can die quickly if you use the laptop from battery often.
Use the laptop with the charger, leave the battery inside, and for example every month, use the laptop from battery 1-2 times, until the operating system says the battery need recharge. This way it can stay conditioned, and not over-used.
But if you forget to use the battery for a long time, it will also decrease it's life! If it stays always at full charge and never discharge, that will damage it.
Most laptops doesn't charge the battery always while you connect the charger, only after the battery reach 90-95% level, then recharge again. So don't worry and just leave the battery inside the laptop at all times.
2. At night, don't connect the charger to the laptop when you stop using it (disconnect the cable). At morning it will recharge that missing 3-10 percent again quickly, that also helps the battery.
3. Today's most common Li-Ion type batteries don't have "memory effect" like the older types, but the charge level can display wrong percent available battery life.
This is because the laptop's BIOS tells wrong data to the operating system, and the battery gauge level needs to be recalibrated.
Some laptops have this option in the BIOS, look for "battery calibration" or "recalibration" and be prepared it will run for a very long time, as it needs to fully charge then discharge the battery again.
Important: start the recalibration with 0% battery level only! If you don't do so, then it will give wrong data about the charge level again. To achieve 0% charge level, do the following:
When the operating system says you have to connect the charger to continue use of the laptop, don't do it just shut down the OS. Then turn on the laptop again, go into the BIOS and wait until the laptop turn off from no more battery charge.
After it turned off, you can connect the charger, and quickly go into the BIOS again to start the recalibration process.
This way it will display the correct charge level again.
Don't let Li-Ion batteries reach 0% charge level unless it's absolutely necessary - like the recalibration - as it can damage the battery!!
4. If you are sure you don't want to store the battery inside the laptop (although I recommend it), then don't store the battery fully charged, or fully depleted. Li-Ion batteries are best stored at charge level between 40-60%, and in a cool and dark place (however not too cold and not too warm, as extreme temperatures are also likely damage it).
Check the charge level every week, if needed charge it before you put it back to the storage again.
If you do like this, then you can have a good chance the battery will be good for at least 3 years.
For me it's now more than 4 years, but maybe I get lucky with this battery. :)
A laptop battery needs more care than a phone battery I think, but you can do similarly with your mobile phone battery.
Extra tip about cooling:
Be careful about not get too much dust in the laptop or near it, and have enough fresh air to be able to cool it down (don't block the air vents and not put anything near the vents, up to 20-30 cm!).
Because most laptop problems come from overheat.
You can also clean the dust from the cooler, just that needs compressed air. Maybe it's a little bit expensive to buy, but it's good for cleaning laptops.
I clean the ventillator of my laptop at least every half year, then it doesn't get too much dust in the cooler.
When you use a laptop, it's ventillator get some dust from the air always (especially if you use it on a bed or a pillow, that blocks the ventillator).
If too much dust get inside in it, maybe the ventillator stops and the laptop overheats.
In this case it's not enough to clean it with compressed air, the laptop needs to be taken apart and the big dust must be cleaned from the laptop's cooler by hand.
