Batteries are more and more essential to your quality of life.
Cell phone batteries may be easy or difficult to replace. A search of YouTube for your particular phone will show how to do it so that you can decide whether it is worthwhile to try it yourself or not.
In one of my phones it was ridiculously simple; in another it was ridiculously complicated. I wish I had checked it out before buying the latter.,
With more and more devices depending on everyday AA, AAA, C and D batteries, It is important to make the right choices.
I maintain AA batteries and attery adapters into which they insert to work as C or D batteries. That means I need to keep fewer batteries on hand, just AAA and AA.
If batteries last a long time in a device, I buy the cheapest, such as Amazon brand. If not I buy a powerful lithium battery or a rechargeable battery, such as for a wireless mouse. All of them AA. Some of these of course require AAA batteries. I avoid such devices if possible.
Rechargeable batteries generally need to be brought up to full charge and allowed to totally discharge completely in the first use. This applies especially to laptop batteries.
Old flashlights can be brought up to date and made much brighter with LED bulbs to save buying a new expensived flashlight.
In a dark closet I have a bright battery-operated LED wall switch. I only use it when getting something out of the closet so the battery lasts a long time.