How safe it is to use fast charging everyday

scc04

macrumors newbie
Original poster
Oct 5, 2017
9
1
Will receive my iPhone 8+ in a few days.

How safe is it to use the fast charging function everyday ? Already bought the 29W USB-C Power Adapter and the necessary USB-C cable.
 

blairian89

macrumors 6502
Dec 5, 2016
379
247
Texas
Will receive my iPhone 8+ in a few days.

How safe is it to use the fast charging function everyday ? Already bought the 29W USB-C Power Adapter and the necessary USB-C cable.
It’s safe to use it everyday if you want to. The phone will control itself to prevent damage - much as it always has on the iPad chargers before.
 
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davidg4781

macrumors 68020
Oct 28, 2006
2,288
199
Alice, TX
I know it says it charges 50% in 30 minutes. Or up to 50%.

What if I plug it in at 65%? Do I get much benefit from fast charging?
 

blairian89

macrumors 6502
Dec 5, 2016
379
247
Texas
I know it says it charges 50% in 30 minutes. Or up to 50%.

What if I plug it in at 65%? Do I get much benefit from fast charging?
A diminished effect, yes.

The charging slows down substantially at around the 80% mark to protect the battery. It is still faster than the 5W power brick that comes with the phone, however.
 

0000757

macrumors 68040
Dec 16, 2011
3,894
849
I know it says it charges 50% in 30 minutes. Or up to 50%.

What if I plug it in at 65%? Do I get much benefit from fast charging?
Basically what they mean is that from 0%, it will only take 30 minutes to charge to 50%. After that it'll still charge faster than the standard 5V included charger, but at a reduced rate, and by 80% it charges at the standard rate.
 
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joeblow7777

macrumors 603
Sep 7, 2010
6,197
7,249
Very safe. Why wouldn't it be safe?
People have weird fear. The other day my girlfriend asked if it’s ok to keep her phone on charge for the whole night.
Theoretically, a battery that charges too quickly or over-charges can overheat and cause a fire (ie. the Galaxy Note 7). Any non-defective device has safeguards to prevent this though. The battery shouldn't take in more current than it can handle, and it should stop drawing a current when it is full.

This may not be what the OP is thinking about, but also theoretically, charging a battery more quickly also puts more stress on it and results in faster wear. I don't know if daily fast charging will have a significant effect on the battery's lifespan though.
 

akash.nu

macrumors G3
May 26, 2016
8,863
10,288
Theoretically, a battery that charges too quickly or over-charges can overheat and cause a fire (ie. the Galaxy Note 7). Any non-defective device has safeguards to prevent this though. The battery shouldn't take in more current than it can handle, and it should stop drawing a current when it is full.

This may not be what the OP is thinking about, but also theoretically, charging a battery more quickly also puts more stress on it and results in faster wear. I don't know if daily fast charging will have a significant effect on the battery's lifespan though.
True. The note 7 issue was just a whacky situation altogether. I try to forget about it. But yeah too many charges will wear out the batter faster. I guess people change the device mostly before it even gets to that point.
 

aakshey

macrumors 68020
Jun 13, 2016
2,243
912
From my experience and what I’ve read, the difference between fast charge and the 5W charger for iPhone is like 5x wear.
 
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macduke

macrumors G4
Jun 27, 2007
10,968
14,675
Central U.S.
It's definitely safe. What I wonder about is longevity.

I've used rechargeable batteries for many years going back to being a kid in the early 90s. From my experience the faster the charge rate, the shorter the lifespan. For a while they kept coming out with faster and faster chargers until they got down to 15 minutes. But those batteries wouldn't last at all. I switched back to slower chargers, but it still wasn't ideal. Then I got a Powerex MH-C9000 WizardOne Charger-Analyzer on Amazon and some quality Eneloop batteries. That charger allows you to basically change the charging speed to each battery in the charger. I've found the sweet spot to be around 700 mA for those batteries.

Now the iPhone battery uses a different chemistry altogether and it's probably more advanced but I still wonder if you did a test of two identical iPhones over time that were consistently drained down to the same level slowly throughout each day to remove variables except one is charged quickly and the other at a regular speed which would would have a longer lifespan? My bet is the slower charge rate but by how much might only be a trivial 1-2% with modern battery technology.
 

bevsb2

macrumors 68000
Nov 23, 2012
1,736
608
Just as an antidotal piece of info, I have been charging my iPhone X for the past 5 months on a 12W iPad charger daily and the battery capacity is still 100%.
 

JPack

macrumors 603
Mar 27, 2017
5,779
8,968
Just as an antidotal piece of info, I have been charging my iPhone X for the past 5 months on a 12W iPad charger daily and the battery capacity is still 100%.
It's hard to make a full observation unless we know the starting capacity.

In some cases, batteries leave the factory with an actual capacity that is above the design capacity. The Apple Store staff have a tool that can read the real capacity, such as 103%. But iOS won't display anything above 100%.
 

davidg4781

macrumors 68020
Oct 28, 2006
2,288
199
Alice, TX
It's hard to make a full observation unless we know the starting capacity.

In some cases, batteries leave the factory with an actual capacity that is above the design capacity. The Apple Store staff have a tool that can read the real capacity, such as 103%. But iOS won't display anything above 100%.
Can’t you use CoconutBattery to show this? Or is it capped at 100% also?
 

IowaLynn

macrumors 68000
Feb 22, 2015
1,556
356
It’s fine. Multiple Samsung, Huawei, Blackberry and iPhone X. Using the Apple USBC to Lightning and fast wireless charger from Sammy, flat and an upright.
 

Julienne

macrumors member
Apr 26, 2018
70
39
Texas
I just use my iPad charger and that seems plenty fast for me. Not spending more on a damn charger.
I've only used the 10W iPad charger for years on iPads and iPhones. The charging speed is faster than the 5W iPhone charger. I don't have exact numbers but I feel like it is 25% or more.
 

aakshey

macrumors 68020
Jun 13, 2016
2,243
912
Fast charging ruined both my previous iPad Pro 10.5 devices.

And from what I’ve read, the people witnessing the most battery degradation with their iPhone X are those using iPad 12W and 29W chargers. While those witnessing the least degradation are the ones using wireless charging or the 5W charger.
 
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