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HappyDude20

macrumors 68040
Original poster
Jul 13, 2008
3,413
761
Los Angeles, Ca
Just got an iPhone 12.
Want to take advantage of fast charging.

I need to buy a charging brick. Local store only sells 18 watt Charger which Apple states a minimum of 20 watts is required for fast charging.

am wondering if I should buy a 20 watt charger or if I should buy something higher such as 30 watts or 50 watts.
 

adamhenry

macrumors 68000
Jan 1, 2015
1,616
610
On the Beach
You are talking about power adapters. They supply power to the charger which is inside your phone. The charger will not charge faster when the adapter is capable of supplying more power than it needs. A lot of people refer to the adapter as a charger causing some confusion.
 

BigMcGuire

macrumors G3
Jan 10, 2012
8,244
10,034
the Alpha Quadrant
The difference between an 18w charger and a 20 watt charger will be very miniscule. Adamhenry is right - the phone will ask what it can take. I don't know off hand what the 12 is capable of asking but I do think it'll take 20w. The differences I've seen in 18w and 20w is minutes.

I've got 65w Anker chargers, 20w, and a slue of MBP chargers. they all charge identically (because the phone will only ask for a certain wattage).

So to answer your question - 85w vs 20w? Not going to be a difference, if there is any, it'll be extremely tiny.
 

BigMcGuire

macrumors G3
Jan 10, 2012
8,244
10,034
the Alpha Quadrant
Found it: https://www.phonearena.com/news/Yes...ne-12-as-fast-as-the-new-20W-charger_id128212

From the website:
1606590785376.png


I'm assuming you already know the whole spiel about how rapid charging is a bit more stress on the battery and can affect longevity - so if you don't have to, it's recommended to charge slower if you can manage it. Within a 2-3 year usage timeframe it shouldn't have a huge impact (imo).

I use a combination of old Anker 5w wireless chargers, 12w chargers, and 18-20w chargers. Sometimes I'll use my 65w Anker charger if it's convenient just for the heck of it. I've got a nice 6ft USB C to Lightning Anker cable. I usually take this traveling (back when I used to for work) as that 1 brick keeps everything charged.
 
Last edited:

macher

macrumors 68020
Oct 13, 2012
2,027
836
Found it: https://www.phonearena.com/news/Yes...ne-12-as-fast-as-the-new-20W-charger_id128212

From the website:
View attachment 1682025

I'm assuming you already know the whole spiel about how rapid charging is a bit more stress on the battery and can affect longevity - so if you don't have to, it's recommended to charge slower if you can manage it. Within a 2-3 year usage timeframe it shouldn't have a huge impact (imo).

I use a combination of old Anker 5w wireless chargers, 12w chargers, and 18-20w chargers. Sometimes I'll use my 65w Anker charger if it's convenient just for the heck of it. I've got a nice 6ft USB C to Lightning Anker cable. I usually take this traveling (back when I used to for work) as that 1 brick keeps everything charged.

The stress over 3 years shouldn’t be relevant. The fact is Apple included a USB-C with the 12. The only solution to purchase is an 18w or 20w anyway. Since this is the case Apple is saying it’s perfectly fine to use a 18w or 20w.
 

Jtludwig

macrumors 6502
Mar 24, 2012
419
300
Just got an iPhone 12.
Want to take advantage of fast charging.

I need to buy a charging brick. Local store only sells 18 watt Charger which Apple states a minimum of 20 watts is required for fast charging.

am wondering if I should buy a 20 watt charger or if I should buy something higher such as 30 watts or 50 watts.

More power! Probably not in this case.

b583246af3a3c6a5b8506723c0dc83cb.jpg
 

Ketsjap

macrumors member
Jan 5, 2007
90
101
Belgium
Isn't it so that not all chargers do fast charging on iPhones? I plugged an iPhone 12 into a 18watt Sony-charger that came with an Xperia 1ii. I did not have the impression that it was fast charging.
 

adamhenry

macrumors 68000
Jan 1, 2015
1,616
610
On the Beach
Isn't it so that not all chargers do fast charging on iPhones? I plugged an iPhone 12 into a 18watt Sony-charger that came with an Xperia 1ii. I did not have the impression that it was fast charging.

Once again, the charger is in the phone. The cube you plug into the wall is a power supply(adapter) for the charger in the phone. An 18 watt power adapter is like any other 18 watt power adapter unless someone is providing false specs.
 
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cbautis2

macrumors 6502a
Aug 17, 2013
879
1,076
The difference in time will be negligible. Fast charging kills the battery faster.
If you can control the heat to 25°C while charging throughout, it shouldn't harm the battery more than using a 5W charger as the charging will switch to trickle charge past 80% regardless of using a fast charger/magsafe/slow charger. However, at those stages, battery temperature while charging is a lot more critical to its health compared to 20-80% where it can tolerate more heat (more current, less voltage) though it's best to keep it at 32°C or lower at those 20-80% charging states
 

macher

macrumors 68020
Oct 13, 2012
2,027
836
No, it does not charge faster. Here are my own personal numbers.


fast charge using 87 watt macbook charger for iphone 12 pro max
15 minutes - 30%
30 minutes - 59%
45 minutes - 78%
1 hour - 88%
1 hour 15 - 93%
1 hour 30 - 96%
1 hour 45 - 98%
2 hours - 100%



similar numbers to https://www.phonearena.com/news/Yes...ne-12-as-fast-as-the-new-20W-charger_id128212

I have the Apple 20w charger. When I charge from let’s say 30% it charges pretty fast to 80% in like 20 - 30 minutes. It does get warm. When it gets to 80% it charges extremely slow as molasses and cools off. So from 30% to 80% it’s very fast and from 30% to 100% it can take over an hour.
 
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BigMcGuire

macrumors G3
Jan 10, 2012
8,244
10,034
the Alpha Quadrant
I too have noticed that this phone charges a lot slower when past 90. It can take forever to get from 95 to 100. I guess this will help the life of the battery. So that’s a good thing. No iPhone I’ve had before charged half this slow past 90 tho.
 

cbautis2

macrumors 6502a
Aug 17, 2013
879
1,076
Trickle charging (high voltage, very low current) is needed since heat output when topping off battery at its highest voltage is a lot more crucial to battery health and your safety. If you don’t have trickle charging programming when topping off, the battery will expand a lot more, generate more heat (due to higher voltage state) and can catch fire. Every charger that’s MFi certified works with trickle charge. It’s just much more noticeable with fast charging than slow charging where you’ll only notice the difference past 95% full
 
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