Do you think the 20-80% rule is as effective as people say to extend your battery life? I'll share my story for more insight.

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Do you think the 20-80% rule is as effective as people say to extend your battery life? I'll share my story for more insight.

The 20-80% rule implies if you keep your phone's battery always between 20-80%, it will drastically increase your phone battery's life span. This is due to many reasons, but I'm not technical enough to explain these. This is what Apple did with iOS 13 (or so I believe, I'm still rocking iOS 12).

Moving forward, let's give you some detail:

On February 2, 2019, my battery was replaced for my iPhone 6S. Afterwards, I purchased an external battery case to keep my battery as close to the 20-80% as I could, with only maybe 5 times (yes, that is an actual number) where I went over the 80% because I forgot to turn off my battery case. It stayed at 100% for quite some time, and the numbers I list below are only known because I check my battery health frequently and take screenshots of said screen.

To clarify again, on February 2, 2019 my battery health stated 100% (as it was just replaced at an Apple store.)
On December 5, 2019, it showed to be at 99%.
On December 20, 2019, it showed 98%.
As of today (January 16, 2019), it now shows 97%.

I can also add that my wife bought an iPhone 7 Plus on March 21, 2019, and it is currently sitting at 92%. She leaves her device plugged in every night, lets it die, and doesn't care about trying to extend the battery as long as she possibly can.

I'm not meaning to sound upset, because I'm not. My battery had lasted 9 months before dropping a single percent.... however, since then, its dropped another 2% in just over a month (or 42 days ago). My methods remained the same (keeping the battery between 20-80%, never letting it die, only letting it go over 80% once, and never under 20%), so what created the extra 2% decrease?

Now I get it, I know my battery wouldn't stay at 100% forever, and I know that this is one of those areas that we don't have a concrete answer. But I just wanted to ask, how reliable do you think the 20-80% rule actually is? It definitely helped extend my battery (for clarity, I bought this phone in October 2017, and it was at 88% on February 2, 2019 before being replaced), but do you think it's a reliable method to actually extend the battery? I'm only asking because it seems that after your battery loses 1%, it starts dropping drastically faster than it should be.

Cheers everyone!

iPhone 6s, iOS 12

Posted on Jan 16, 2020 1:53 PM

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Answer 1

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Androish

Level 8

39,487 points

Jan 16, 2020 1:58 PM in response to DimitriH

Keep in mind that the % showing full charge capacity is also just an estimate.

Also you might have started with more than 100% say like 104% and it would still show 100% until dropping under 100%

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Answer 2

Jan 16, 2020 1:59 PM in response to DimitriH

I have never, with any iDevice, subscribed to any charging rule. I charge when it works for me, I disconnect from the charge I when it works for me, I seldom, if ever have seen the battery percentage below 10%. My 3.5 year old iPhone SE is at 95% life. My 8 year old iPad still get 8-10 hours of battery life.

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Answer 3

y_p_w

Level 6

17,684 points

Jan 16, 2020 2:27 PM in response to DimitriH

As a technical matter, of course limiting the charge range will improve rechargeable battery longevity. There are larger devices (including those sold by Apple) that have a rated 1000 charge cycle to 80%, while there's nothing that would indicate that there's any better quality to the battery or charging system. I suspect that with larger batteries they can increase the relative margins so that 100% is a little bit lower and 0% is a little bit higher.

But it's a huge pain to try and keep a battery within a range manually. It's a lot easier if it's automated, such as with some devices that can be configured to use less of the battery range.

Still - single anecdotes are notoriously unreliable. I've got an iPhone 7 with the battery replaced in Nov 2018 under Apple's $29 (US) promotional program. It's currently showing about 215 cycles (from coconutBattery) and the official Settings battery health is still 97% although the coconutBattery health reading varies. I have done nothing to try and limit the charge range. I've let it drop to 0% several times and I leave it connected to a power adapter overnight almost every night. I almost always charge it in a silicone case, and it's even gone into thermal protection mode a few times when exposed to sunlight in my car. Nothing special done, although I have used USB power packs to extend daily operating time. However, I've had my battery longer than yours and it's still showing 97% like yours after being replaced earlier. I can't figure out why this battery won't die, but I'm not complaining.

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Do you think the 20-80% rule is as effective as people say to extend your battery life? I'll share my story for more insight.

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