How to Charge the Battery on Your Laptop
Charging your laptop battery is easy to do: Plug the laptop into a wall socket, and the battery begins to charge. Internally, the laptop switches from battery (DC) power to AC power, and the power-management hardware inside the laptop begins to recharge the battery. The battery continues to charge, even when the laptop is turned off.
You can recharge your laptop’s battery whether the battery is fully drained or not. Especially if your laptop is using a lithium-ion battery, it makes no difference. However, NiCad and NiMH batteries benefit from being fully drained before they're recharged. That type of battery lasts longer and retains most of its potency if you fully drain it.
Note that lithium-ion batteries have a rapid-charging option. This option is available either on a custom tab inside the Power Options dialog box or through special battery software that came with your laptop. In a pinch, a rapid charge can save time. Otherwise, you want a nice, full, slow charge for your laptop's battery.
It's been said that if you’re using a laptop while you're charging the battery, it takes longer to recharge the batteries than when the laptop is turned off. This might have been true once, but it’s no longer true; feel free to use your laptop while the battery is charging.
Never short a battery to fully drain it. To short means that you connect the two terminals (positive and negative) directly so that the battery simply drains. This is very bad. It can cause a fire. Don't do it.