It isn't always possible to be near an outlet to keep a charger running. A laptop is supposed to be portable. But a user may still need to be on their computer more than just 2 or 3 hours their batteries allow them. That can turn into a real problem if the person can't keep their computer running because lithium stock its battery just died.
On top of this wireless fun your iPad comes with Bluetooth EDR ahh yes rubs of chin all round what the heck is all this stuff anyway the upshot of which lithium facts is that you can connect it to accessories like wireless headsets headphones or the Apple Wireless Keyboard if that happens to particularly float your boat.
ONickel Cadmium (NiCd) - The oldest battery type used in cell phones. They are the heaviest and lowest capacity battery type. These can be somewhat hard to find.
Laptop computer uses If you keep the lithium bettery stock battery in your laptop for everyday use and power it from the wall socket unplug the power every few days and let it run off the battery as a battery at capacity lasts longer than one at capacity if you don't travel with it you should remove the laptop battery when on fixed power.
Now you want to discharge the battery. If you disable the hibernation setting or anything else that might make the computer go into power saving mode, it would be better. Let the computer run until it shuts down due to loss of battery power, then turn it back on.
Recharge the battery to full again and repeat the above steps a few more times. This will allow you to use the battery for a longer time and you can do this no more than once a month. Replacement batteries can be expensive and stretching out their use when you are on a budget can help.