The problem with Li-ion batteries is that they are incredibly unstable. As soon as they have been manufactured they will start to wear out, even when they haven’t been used yet and are kept at the depot or on the shelf. When using your battery, you will realise that after a few charge cycles, the battery won’t be able to last as long as it used to when you first started using it. Eventually, it might only hold half the charge it used to, or even less. There are ways that you can slow down this battery deterioration by looking after your Li-ion the right way. All batteries wear out faster when they hold a larger charge or are subjected to higher temperatures. If your battery is kept at too low a charge, it can damage the battery as it continues to slowly discharge in storage.
If you are using your laptop whilst plugged into the mains on AC power, where possible, remove the battery as the laptop gets quite hot and this can slowly damage the battery and cause faster battery deterioration. If you are afraid of a power cut, then leave the battery plugged in but charged at 40%. Getting yourself a surge protector is also a good idea. Charge thresholds can generally be set on the advanced options of most battery manager software. Do not leave the battery in the laptop at full charge in such a hot environment. Once you’ve removed the battery, store it in a cool dry area, between -15 degrees to 20 degrees, with around 0 being roughly the optimum. Putting it in the fridge is fine but make sure the battery doesn’t get damp as a result. I'd recommend just storing it in a cool cupboard somewhere. Less hassle.
If you intend to store the battery for a longer length of time as you are using mains power a lot, then set the charge of the battery at 40-50% and store it as above. Avoid exposing the battery pack to excessive heat.
Now, ideally, it is best not to discharge the battery past 20% or to charge it past 90%. Charging the battery to the full capacity wears it down a lot faster and as the final stages of charging take longer, it is also much more time consuming. Unless you need to use the full capacity sometime soon, it is best to keep it within the 20% to 90% range. The last 10% charge probably won’t affect you much. When charging, it is also best to have the laptop switched off to have a cooler charging environment. Also, NEVER discharge to 0%. If you really need to, discharge it to 5-10%. If you've somehow managed to get yourself in a danger zone of battery life, hibernate your laptop. It is faster than a shutdown and you save your work.
I appreciate how much of this would not seem practical to everyone but it is much better to have your battery pack still hold 90% of the full charge after a year of use than be down to 50-60% and have to purchase a new one a lot faster. If your battery is clearly not holding the charge it is displaying, then recalibrate it. The software will normally guide you through this, but this is the only time when it is necessary to do a full discharge and recharge.
Some people don't seem to appreciate that batteries are consumables. They won't last forever and every battery has a specific lifespan. Plus, battery failures are unpredictable. When buying batteries, be sure to check the date of manufacture. Buying a battery manufactured in 2006 that has been kept on the shelf for 4 years will probably mean that the battery will have already lost capacity and won’t hold the manufacturer design capacity. When transporting your battery packs around, make sure they don’t bash into things as Li-ion batteries have been known to explode. Particularly, Sony and Sanyo cells have been heavily implicated whereas Panasonic cells are deemed somewhat more reliable. Using third party batteries can also void your warranty, so it is best to check if the battery is genuine if purchasing. If your battery fails and is under warranty, then get it fixed, but the warranty on the battery is usually less than the warranty on the system.
To get the most out of your battery in terms of battery running time, tailor your computer settings to what you are doing. Close down WWAN/WiFi/Bluetooth radios if you do not need them. Turn screen brightness down. Mute the sound. If you happen to have switchable graphics, switch it to the energy saving profile. The battery software or the windows power schemes should generally take care of the rest such as turning off Aero on Windows 7. Windows 7 has a good battery manager with the OS. Also remember to turn the screen off when you’re not using it - don't have some screensaver just because it looks cool. Have it hot keyed so it’s easy for you to quickly access or set it so it switches the monitor off when you close the lid. Basically, turn off any unnecessary device that you're not going to use so the battery draws fewer Watts every hour. Go into device manager in the control panel to do this. If you have an antivirus software, set it so it doesn't do scheduled scans when you are running on battery. There are more advanced options you can take such as forcing your CPU to lower speeds or getting a HDD with a lower power consumption, but generally it's not worth the effort. Oh, and Linux is great for battery life!
To prolong battery life:
- Remove battery when running on AC due to heat
- Avoid exposing the battery or the laptop to too much heat
- Unless you need the full capacity, avoid charging past 90% and avoid discharging past 20%
- Shutdown your laptop before charging to keep the heat down
- Store the laptop battery ideally at 40-50% capacity in a cool and dry place (just put it in a cupboard somewhere)
To prolong battery run-time:
- Switch off WWAN/WiFi/Bluetooth radios if they're not needed
- Turn the monitor off when you're not using the laptop for a while
- Turn off unnecessary devices you don't need