Users on iPhone support forums are constantly worrying over battery health. It’s not uncommon to see posts through the Apple support ecosystem with iPhone users worrying over measurements like 95 percent or higher. That’s natural and understandable: battery health appears to be a clean and reliable indicator of how your battery is doing. After all, without a good battery, your phone is just a paperweight. And Apple didn’t take all that flack about iPhone batteries over nothing, right?
It might surprise you to learn that battery health is a reliably bad indicator of your battery’s performance. It doesn’t predict future problems, nor does it give you a good sense for how long your battery will last from today. But thanks to the illusion of insight it provides, users cling to battery health indicators as reliable measurements. Unfortunately, they’re anything but.
What Is Battery Health?
Batteries are harder to measure than you might expect. Even something routine – measuring the battery’s current charge – produces significant errors and inaccuracies. Any measurement is a rough approximation at best. Phones can only measure your battery capacity precisely to a point.
Worse still, the battery’s organic chemical makeup introduces organic errors that cannot be overcome. Your battery’s capacity might vary by a couple percentage points each time you charge it, sometimes as much as 10 percent. So any measurement you see could miss the mark by as much as 10 percent.
Consider a concrete example. Imagine your battery had a brand-new capacity of 3000 mAh. Today, your battery holds 2880 mAh. Your phone reports this as “96% battery health” because your battery can now only hold 96 percent of the original capacity. Supposedly, this number approximates battery degradation and therefore battery status.
Does Battery Health Matter?
All batteries degrade. Chemical components break down, reactions slow, catalysts fizzle. On a long enough timeline, every battery will eventually lose enough capacity to fail. Nothing can escape the ravages of entropy. As a result, health will gradually decrease no matter how much you baby it. It’s both expected and unimportant.
Fortunately for us, today’s lithium-ion batteries last for ages before degrading a meaningful amount. For most people, your iPhone’s battery lasts longer than the device’s useful life. The battery’s health measurement will gradually decrease over time as the battery decays, but this is both expected and normal. Shop for enough second-hand iPhones, and you’ll see plenty of devices with battery percentages ranging between 90 and 95 percent.
So we have an inaccurate measurement that doesn’t tell us what it purports to while encouraging concern over a non-issue. Battery health isn’t completely irrelevant, but if battery health and irrelevancy were at a party together, battery health would be standing uncomfortably close.
In most cases, battery health tells you as much about the battery’s failure rate as the Dow Jone’s Industrial Average tells you about the nation’s economy. As any stockbroker will tell you, the Dow bears only a casual relationship to reality.
Basically, you can safely ignore any measurement of battery health above about 80 percent. Anything above 90 percent is perfect functionality. Only when your battery’s health gets low and stays low consistently should you be concerned. Anything consistently below roughly 80 percent is worth being examined by a professional at an Apple Store or an Apple-certified service shop.
If Battery Health Doesn’t Matter, What Does?
Battery health is a pretty poor measurement of how functional your battery is. The fact is, health is not a reliable indicator of present or future problems with your battery. The only thing it can reliable measure is the average maximum capacity of your battery, which will be expected to fluctuate natural, considering the errors that organic chemistry invites into the mixture.
If we can’t use battery health to gauge a battery’s duration, what can we use?
The gold standard of battery problems is and always will 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 a substantial percentage of charge remaining? Do basic operations suddenly take twice as long?
Those symptoms indicate battery problems reliably and accurately. Ironically, your phone might even indicate great health in the midst of these issues. That gives you a great idea of how importance battery health measurements are when it comes to determining the health of your iPhone.
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