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 ion battery stocks 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.
The price of an external laptop battery may vary from brand to brand. But they are quite affordable and very compact device. They can be recharged with an external charger so you don't have to look out for an electric supply to charge the external battery.
Agitate the lithium bettery stock water gently until the light tells you it's done. UV purifiers don't work in murky water, so if that's the only water you have, you'll have to pre-filter it until it's not cloudy. You also need to make sure you don't drop a UV device.
Li-ion cells have a good peak output current and low source resistance. When you overload the tool, the voltage stays up, and they just keep pumping current into the motor. Power tools have thermal overload trips in the motors, and that's a good thing with Li-ion batteries, if they didn't they'd just burn the motor out!
Today, many of the latest computers have a fast recharge feature where you can recharge 90 percent of the battery power by charging it for around one hour. The balance 10 percent is recharged slowly. If your laptop has this facility, do use it. This helps to extend the life of the battery. However, do not recharge the laptop battery until it has less than 30 percent charge remaining.