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Super Fast Charging being slow

(Topic created on: 24-06-2021 07:03 PM)
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ConorDavies
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Hello, I got the S21 Ultra a few days ago and have been charging it with the standard "cable charge". I got the 45W Super Fast Charger today, plugged it in and to my surprise the charging speed hasn't improved. At 90% with the cable charge it says it would take 30 minutes to charge the last 10%, when plugging in the Super Fast Charger it's exactly the same, 30 minutes just to do 10%, why is it doing this?

And yes "Super Fast Charging" appears when I plug in the new charger. 
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17 REPLIES 17
John19691969
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S21 ultra is not 45 watt charging because it can only charge max 25w I've S20 ultra which can do 45w charging will say super fast charging 2.0 when I use 45w . When I use 25w it just says super fast changing
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John19691969
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S21 ultra charging spec max 25wattScreenshot_20210625-002620_Samsung Internet.jpg
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John19691969
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S20 ultra charging spec max 45 wattScreenshot_20210625-002908_Samsung Internet.jpg
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-Robot-
Samsung Members Star ★
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I was thinking the same, I didn't think 45w charging was supported on S21 Ultra

I do know if you use 25w charger with USB C to USB C on the Ultra you get slightly faster charging then reg USB to USB C
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SgtRepeat
Explorer
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What's your room temperature when you charge the phone? Strangely, that affects the charging speed of the S21 Ultra a lot. 

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D0rkiishchris
First Poster
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Super fast charging won't use all the available mA once the phone battery gets to 30C.  And my phone from dead will super fast charge if it's off or if it's been dead so the temperature is ambient.  Once the phone is on and the battery gets to about 18%, it will be over 30C.  Super fast charging on my S20 FE slows down once it is at 30C.  I put the phone in front of my AC vent, got it back to 27C and it started super fast charging again.   I think SFC is most useful for a dead phone and limited time to get something in it before you leave thehouse.  I'm using a Samsung 45W charger from a Samsung chrome book and a program I use called ampere shows that it hits 5000 mA.

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D0rkiishchris
First Poster
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I think the magic temp. Is actually 34 or more.  Then it has to go below 30 to start super fast charging again.  I just tested this.  However, the phone will still say super fast charging.  Even though it's not charging anymore than with the fast charger that comes with the phone

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D0rkiishchris
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Screenshot_20211115-110255_Ampere.jpg

Screenshot_20211115-110125_Ampere.jpg

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