Originally Posted by bevolasko
If your computer isn't working properly without the charger then the battery may need replacing. Normally, a healthy battery should boot up and power a computer without the charger. Batteries eventually wear out over time and do so quicker if they get charged more frequently.
Here are some tips to extend battery life: How to Extend the Life of a Laptop Battery: 10 Steps
Tips 6 & 7 are wrong.
6. With Lithium Ion batteries, you should NEVER allow it to fully discharge. Doing this can actually hurt the battery and damage internal circuits. When it's low... plug it in.
7. Again, with Lithium Ion, this does not matter. Li-Ion batteries have internal circuits that prevent overcharging (which is what used to happen with Ni-Mhd batteries). Leaving a laptop with a Li-Ion battery plugged in 24/7 will not hurt it. The circuits will switch over to a "trickle charge" and only charge little by little when small amounts of battery get used up.
Read here for more info (mainly geared towards smartphones, but also has relevant info to laptops and all Li-Ion batteries): Useful Lithium Battery Information