Users of smartphone tech support forums constantly worry about battery health. It's not uncommon to see publications worrying about metrics like 95% or more. And that's natural and understandable:battery health seems like a clear and reliable indicator of your battery's health, and without a good battery, your phone is just a paperweight. But battery health is barely relevant to your device's health and almost always wrong anyway.
All batteries degrade. Chemicals break down, reactions slow down, catalysts fizz. Over a long enough timeline, each battery will eventually lose enough capacity to fail. Nothing can escape the ravages of entropy. As a result, battery health will gradually decrease no matter how much you feed it. This is both expected and unimportant.
Luckily for us, today's lithium-ion batteries last for centuries before degrading significantly. For most people, your phone's battery lasts longer than the useful life of the device. Battery health will gradually decrease over time as the battery degrades, but this is both expected and normal. It is not uncommon to sell or recycle a phone that is at 90% battery after years of use.
So we have an inaccurate measurement that doesn't tell us what it claims while encouraging worry about a non-issue. Battery health isn't completely irrelevant, but if battery health and irrelevance were brought together at a party, battery health would be uncomfortably close.
In most cases, battery health tells you as much about the battery failure rate as the Dow Jone industry average tells you about the nation's economy. As any stockbroker will tell you, the Dow Jones bears only a casual relationship to reality.
Basically, you can safely ignore any battery health reading above about 80%. Anything over 90% is perfect functionality. It's only when your battery health gets low and stays low consistently that you should be concerned. Anything consistently below about 80% is worth looking into.
If we can't use battery health to gauge how long a battery lasts, what can we use?
The most reliable indicator of battery health will always be user experience. If you're worried about your battery, keep an eye out for some classic signs of battery failure. Does your phone suddenly die with 30% charge remaining? Do basic operations suddenly take twice as long? These symptoms reliably and accurately indicate battery issues. Ironically, your phone may even show excellent battery health amid these issues. And that alone tells you everything you need to know about battery health accuracy.
