Changing an iPhone battery takes skill, patience

Have you noticed that your iPhone doesn’t work for as long as it used to?

If you check your phone’s battery system preferences, you might find that the battery life has dropped to 80%, meaning that 20% of the phone's battery capacity is gone

You could take the phone to the Apple store and see about getting a new battery, but if you have a certain degree of technical skill, why not try installing the battery on your own?

Apple charges $49 to swap out iPhone 6S batteries, for example, which is reasonable. They'll usually do it while you wait, but you have to make an appointment through Apple.com.

Buying a replacement battery from Amazon costs only $20, and it comes with all the tools you need and instructions.

Opening an iPhone is not for the faint of heart. There are two very tiny screws next to the Lightning port to remove, then you attach a suction cup on the lower left side of the screen and pull up until the screen separates from the phone's body.

Once the screen is separated, you wedge in a small plastic pry tool that looks like a guitar pick and carefully pry up the screen, lifting it toward the top of the phone.

Be careful: There is a cable attaching the screen to the phone up near the top of the screen.

It’s best to keep the screen connected to the phone at a 90-degree angle by leaning it against a drinking glass or something similar while removing the battery. There are two tiny screws to remove and a cover to take off before you can remove the battery cable.

Once the cable is free, the battery is held on by two adhesive strips. They can be removed by pulling down on them to stretch out the adhesive, just like removing a 3M Command strip. The key is to keep stretching and don't stop or the plastic strip will break.

If the strip breaks off, you'll need to carefully pry up the battery, but only use a plastic pry tool and don't bend the battery too much, as puncturing it can start a fire. Pry carefully and slowly, and you'll be able to get the battery out.

Reinstallation is the same steps in reverse.

Install the included adhesive strips on the new battery, peel off the plastic from the strips, stick the battery into place and plug in the cable. Put back the cover, screw in the two screws, then lower the screen back into place. It will snap back securely. Then reinstall the two tiny screws by the Lightning port, and you're done. And with any luck, you should get another year or two out of your iPhone.