Yes, its better to use all the battery before charging. It prolongs your battery life. Not sure why, But all the cameras say to do that.
Different cameras take different batteries, you might be able to use it on another camera, but its not likely. You have to check each camera.
It is always a good idea to have a spare en el1 battery. Many people will just buy one, assuming that they can easily buy another if the first one wears out. While they are correct, this can be very inconvenient. You never know when the battery is going to wear out, after all. You never know if you are going to lose it. These types of things cannot really be planned for, so all that you can do is make sure that you have a spare battery to use the moment that you need it. It is worth paying a little more.
you can go to iibattery.com,
its on the distributor
Sae.en
The best battery for a Nikon D7100 camera is the EN-EL15 rechargeable lithium-ion battery.
One can buy an AGM battery at online stores such as "Battery Stuff", "Battery University", "DC Battery", "Humminbird", "Greenlink" or "Whole Sale Solar".
Buy a new battery or call someone to jump your battery
Battery as in assault and ---- Aggression Battery as in my car's --- is flat Batterie My flashlight needs a new ---- Pile
You could buy a USB battery pack from many reputable retailers. This includes Amazon, Best Buy, TigerDirect, Buy, and Newegg. All of these retailers offer a USB Battery pack.
buy a new battery.