https://upload.wikimedia.org/wikipedia/commons/c/c4/Electric_batteries.jpg

Doing the right thing while keeping powered up 

Most portable or mobile devices need power and that is provided by batteries in some form – either rechargeable or non-rechargeable, built-in or replaceable. 
All of those batteries have their advantages and disadvantages, some last longer than others, some are cheaper in the long-run, some need more attention than others i.e. charging or replacing. 
Whatever the battery, it will need to be replaced at some stage