How to optimize reducing a device's max. battery capacity without damage

March 12, 2024 6:06 AM

My phone battery capacity went down to 80% over the first 20 months but has since, for whatever reason, been magically hovering there for the last six months. It seems stuck at the magic 80% level no matter what. Three things I have tried: 1) disabling optimized battery charging; 2) cycles of running the phone until the battery is discharged; 3) leaving the phone connected to power after fully charged. What are other ways I can operate a device to optimize speeding the process of reducing its battery's capacity below the 80% threshold, without voiding the device warranty?
posted by They sucked his brains out! to Computers & Internet (21 answers total)

Sorry, I'm a bit confused - are you concerned about battery health? Some of the things you're doing, like disabling optimized charging, are going to decrease the longevity of the battery.

Others, like leaving it plugged in after charged, won't have any effect (choosing whether to charge the phone is a different process than just plugging it in, otherwise the above optimized charging wouldn't work), and I'm not entirely sure that fully depleting your battery is good for it.
posted by sagc at 6:29 AM on March 12

Response by poster: Let's just say that, for reasons, I would like to get the battery capacity under 80% as described in the question.
posted by They sucked his brains out! at 6:31 AM on March 12

Do you mean that the indicator that shows how much the battery is charged, never goes above or below 80% no matter how much you use it or charge it? Is it possible that the indicator is not showing the true battery charge?
posted by Zumbador at 6:31 AM on March 12

Response by poster: The capacity is listed at 80%. The charge level is displayed as a value between 0% and 100% (of capacity). To clarify, I am talking about battery capacity listed in system settings, not charge level.
posted by They sucked his brains out! at 6:34 AM on March 12

So you want to basically wear your battery down? I would think constant charging to max an then draining the battery. Eventually that would do it. There's also the possibility that the battery capacity isn't being accurately reported, you could find other ways to measure it. Also cold/warm temps may be bad for batteries?
posted by MisantropicPainforest at 6:37 AM on March 12

Response by poster: I would think constant charging to max an then draining the battery. Eventually that would do it.

I would have thought so too; please see what I have tried in the question.

There's also the possibility that the battery capacity isn't being accurately reported, you could find other ways to measure it.

There is that possibility. If so, what are ways to measure the true capacity of the battery independent of what the operating system is reporting, without voiding the warranty?
posted by They sucked his brains out! at 6:40 AM on March 12

Are you concerned the capacity's not going down? I doubt it will go up.
I've had my iPhone 3 years and it's at 82%.
posted by MtDewd at 6:40 AM on March 12

Response by poster: For reasons, I would like to get the battery capacity under 80% as described in the question.
posted by They sucked his brains out! at 6:42 AM on March 12

I would think constant charging to max an then draining the battery. Eventually that would do it.

I think the opposite. Charging the battery when it does not need charging will give you the desired result, I imagine.

So, leaving the phone plugged in for as long as you can and letting it drain to 60% and then fully charging and repeating this would have that result.
posted by dobbs at 6:43 AM on March 12 [1 favorite]

There are third party apps that will measure the battery life for you. I don't know if they produce independent results from the OS. You could also time how long it takes the battery to die after fulling charging and running the same app. It could be that the battery just won't wear like you want it to rather than the OS reporting the same number regardless of battery health.
posted by MisantropicPainforest at 6:44 AM on March 12

Response by poster: I apologize if my question is unclear. I'd like to gently ask if people can respond without guessing. It is okay if you do not know the answer.
posted by They sucked his brains out! at 6:47 AM on March 12 [3 favorites]

Understanding your reasons may help us give you the answer you want. Are you wanting to get it under 80% so you can force Apple to replace it?
posted by mrgoldenbrown at 6:48 AM on March 12

Best answer: My understanding, based on the sources cited by the excellent Accubattery app, is that repeatedly charging a phone battery from just below 100% to 100% is pretty much the worst thing you can do it.

For example, charging from 93 to 100% causes as much wear as charging from 0 to 93.

So never let it get below, say, 90% without charging.

Of course, if your phone OS happened to manipulate its health stats to avoid paying out on warranty claims, there is only so much you can do.
posted by Klipspringer at 7:02 AM on March 12

Best answer: Charging or discharging the battery at temperatures below 0°C (32°F) or above 45°C (113°F) will cause degradation (source). (Note that charging/discharging the battery will raise its temperature, so the ambient temperature may need to be lower than the numbers above.)

In storage, the battery will degrade faster if it is near 0% or near 100% charged, and degrade slower if it is near 50% charged.

Deliberately placing high stress on a lithium ion battery might make it more likely to fail catastrophically and cause a fire.
posted by mbrubeck at 7:03 AM on March 12 [1 favorite]

Warranty / AppleCare reasons I presume. IIRC 80% is the magical number that when under, Apple will repair/replace the battery.

You've already marked similar best answers, but I've definitely seen wild temperature swings affect the battery on my phones over the years; leave your phone on a mount in direct sunlight on the dash of your car and it can overheat very quickly.
posted by cgg at 8:29 AM on March 12

Discharging to 0% is the worst of the ordinary, non-dangerous, everyday practices that will degrade a phone battery, more so than charging to 100% (though that’s not great either).

Leaving it at 0% for an extended period of time — months in the case of something like a phone — will eventually drain the “reserve” voltage that modern batteries still have even at 0%, at which point the battery chemistry will be pretty irretrievably ruined and won’t take a recharge.
posted by theory at 8:31 AM on March 12

If the 90% to 100% charge is so bad, or maintaining at 100%, then how do car battery maintainers work?

Not lithium, I’ve had great (undesired) results ruining car batteries with ultra-low cycling in extreme temperatures👌

I’ve also found that “battery capacity”, like you’re talking about, based on voltage, reads differently depending on charge level.
posted by rubatan at 10:55 AM on March 12

If the 90% to 100% charge is so bad, or maintaining at 100%, then how do car battery maintainers work?

Lead-acid car batteries have very different characteristics from lithium-ion phone batteries.
posted by mbrubeck at 12:05 PM on March 12 [4 favorites]

I would let it get and stay hot. The people I know who go through phones fastest are people who are not permitted to carry their cellphones into work with then and leave them in their cars.
posted by Vigilant at 1:54 PM on March 12

I've used the coconut battery app in the past to assess health of my macbook/iphone battery. So that might be worth checking out, to give some outside evidence about whether that 80% is accurate or not. (Of course, if an independent app doesn't agree with the iOS assessment of the battery, not sure if that will help you with AppleCare warranty...but it's still likely helpful info to have.)
posted by litera scripta manet at 4:33 PM on March 12

Best answer: I gotta think you are actually me, wondering why my MacBook Air battery was stuck at 84% capacity for most of 2023 (and still is!). I even got extended AppleCare+, waiting for the magic 79% number because at $65 a year it's cheaper than replacing the battery for $180 or so. I will need to get creative but safe as well, I fear.
posted by lhauser at 7:40 PM on March 12