Fast battery charging - Xiaomi Redmi Note 4 Questions & Answers

Hi friends!
I'm not an expert, but to me, this seems very strange. I understand that the Redmi Note 4 supports fast charging, but how fast is that actually and how does it work? For example, with the stock charger which is 5V and 2A, my phone from 1% to 100% is charged in about 1 hour and few minutes. The battery is 4100mAh , so for the stock charger it would take approx. 2 hours (plus-minus). Can anybody explain to me how the hell is my phone charged in around 70 minutes? In the different roms, there were different charging times, actually longer. Now with the AOSP custom rom, my phone is fully charged in around 1 hour. Not that i'm complaining, i'm just curious.

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That's an interesting question.
I always have known it to be:
>4100maH Battery
>Charging at 2A
Therefore:
4.1AH / 2A = 2.05 hours
Sent from my Redmi Note 4 using Tapatalk

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Wilderone said:
4.1AH / 2A = 2.05 hours
Click to expand...
Click to collapse
Math, the Queen

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Fast charging depends on processor capability. Redmi note 4 have 625 SD processor which supports quick charge 3.0. If you go for higher end phones with 8XX Snapdragon processor they have quick charge 4.0 , it will even take less time to charge. You can google about the science behind this, but to the best of my knowledge quick charge 3.0 passes higher current minimizing resistance during charge process. One small detail you can notice, fast charging charges battery upto 80% pretty faster & after that speed of charging slows which is needed to prevent battery from exploding. Almost all fast charging adv says "0-80% in xyz miniutes", hardly anyone advertise 0-100% in xyz mins.

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Could you mention, which rom are you using?

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as far as i know, 625 supports QC 3
but xiaomi didn't activate it in the kernel hence only QC 2 is working...

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Are you getting the same 10 hours of SoT in 1 full charge?
If yes, then what ROM / Kernel you're on?

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People are here in this forum randomly talk about SOT & VULCAN API i highly appreciate if anyone explain... Thanks

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SoT: Screen on Time, the time you can use your phone with the screen is active e.g. watch a video, text someone...
There is a difference between between SoT and Standby time. You can have a SoT of 12 hours while you carry your phone around 2 days.
Vulkan API: I refer to Wikipedia : https://en.m.wikipedia.org/wiki/Vulkan_(API)

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Very fast!!
Could you please share Rom and Kernel version ?

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Yes my battery also charges quite fast on stock Miui rom & the charging graph looks quite straight up but not as fast as turbo charging of moto. Though I never reached below 53% yet because my screen on usage per day on average is 6.30hrs and I get it there by 53%
One thing I'd like to know if it's for everyone.
As I power on the charger connecting to the phone it generates some hiss sound. Listen up closely.
But if I power on charger without connecting phone then there is no such sound.

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ekin_strops said:
Hi friends!
I'm not an expert, but to me, this seems very strange. I understand that the Redmi Note 4 supports fast charging, but how fast is that actually and how does it work? For example, with the stock charger which is 5V and 2A, my phone from 1% to 100% is charged in about 1 hour and few minutes. The battery is 4100mAh , so for the stock charger it would take approx. 2 hours (plus-minus). Can anybody explain to me how the hell is my phone charged in around 70 minutes? In the different roms, there were different charging times, actually longer. Now with the AOSP custom rom, my phone is fully charged in around 1 hour. Not that i'm complaining, i'm just curious.
Click to expand...
Click to collapse
you need battery calibration.Your battery_stats is messed up after all the rom flashing.Download a battery calibration app
You can't charge this phone in one hour.

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Based on the latest Miui8 development version changes, keep the original, no replacement for any official app, partially built-in streamlined
The use of self translation kernel, CPU can be overclocking to 2.2g, GPU can be overclocking to 700, the default does not exceed, open the performance mode will automatically overclocking
Supports f2fs and supports only data and cache partitions
Open fast flush support, use qc3.0's head charge status bar will show fast flush icon, the first use must complete shutdown, then reboot will be effective, direct restart invalid
With 5 charging head test voltage current at around 6.2, at about 2.8, the temperature at around 46
Don't wash fast charge when playing, Caution!, attention to the heat
Android core crack, can be free to delete the millet frame kami
Turn on camera street beat mode to optimize imaging effect
Integrated ROOT, Shuangqing after failure, re Su can brush card
I've been using it for over a month, and it doesn't have any problems. It can be used safely.
I sent it here and I hope it will be able to recompile it so that it can be used on all ROM.
Because this kernel can only be used on the author's ROM, there will be no WIFI if you brush the kernel on other ROM.
It can also be used on the AEX ROM, but it's also a kernel modified by someone else.
I asked a few great gods, they said that the kernel is matched with the WIFI, and then nothing.
I sent it here in the hope that a great God can fix it and use it, and I'm not afraid of the danger. Let me be a white mouse. If you can, I want you to contact me and let me do the test.
We all use QQ in China. My number is 371632477. Through it, you can find me.
I have no way to send address links in the forums
Reprinted from (jun-ao) large self translation fast charge package
---------- Post added at 03:50 PM ---------- Previous post was at 03:49 PM ----------
在中国有一个作者他自编译了一个快充内核
QC 3.0的内核，他充电只需要一个小时左右。
---------- Post added at 03:58 PM ---------- Previous post was at 03:50 PM ----------
Here is an address, which is compiled by a Chinese author of the fast charging kernel 3. The addresses will be sent out separately because I can't send the link
pan.baidu
---------- Post added at 03:59 PM ---------- Previous post was at 03:58 PM ----------
pan.baidu
.com/s/1bpao02N
Connecting the two together is the address of the ROM
---------- Post added at 04:09 PM ---------- Previous post was at 03:59 PM ----------
I don't know how to upload pictures I use now is AEX the ROM also used his kernel fast charge as long as 1 hours or so WIFI and AEX the ROM supporting so can use WIFI but in other ROM do not use if you can help me to repair it will be a good kernel if you need the kernel add my QQ 371632477

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371632477 said:
Based on the latest Miui8 development version changes, keep the original, no replacement for any official app, partially built-in streamlined
The use of self translation kernel, CPU can be overclocking to 2.2g, GPU can be overclocking to 700, the default does not exceed, open the performance mode will automatically overclocking
Supports f2fs and supports only data and cache partitions
Open fast flush support, use qc3.0's head charge status bar will show fast flush icon, the first use must complete shutdown, then reboot will be effective, direct restart invalid
With 5 charging head test voltage current at around 6.2, at about 2.8, the temperature at around 46
Don't wash fast charge when playing, Caution!, attention to the heat
Android core crack, can be free to delete the millet frame kami
Turn on camera street beat mode to optimize imaging effect
Integrated ROOT, Shuangqing after failure, re Su can brush card
I've been using it for over a month, and it doesn't have any problems. It can be used safely.
I sent it here and I hope it will be able to recompile it so that it can be used on all ROM.
Because this kernel can only be used on the author's ROM, there will be no WIFI if you brush the kernel on other ROM.
It can also be used on the AEX ROM, but it's also a kernel modified by someone else.
I asked a few great gods, they said that the kernel is matched with the WIFI, and then nothing.
I sent it here in the hope that a great God can fix it and use it, and I'm not afraid of the danger. Let me be a white mouse. If you can, I want you to contact me and let me do the test.
We all use QQ in China. My number is 371632477. Through it, you can find me.
I have no way to send address links in the forums
Reprinted from (jun-ao) large self translation fast charge package
---------- Post added at 03:50 PM ---------- Previous post was at 03:49 PM ----------
在中国有一个作者他自编译了一个快充内核
QC 3.0的内核，他充电只需要一个小时左右。
---------- Post added at 03:58 PM ---------- Previous post was at 03:50 PM ----------
Here is an address, which is compiled by a Chinese author of the fast charging kernel 3. The addresses will be sent out separately because I can't send the link
pan.baidu
---------- Post added at 03:59 PM ---------- Previous post was at 03:58 PM ----------
pan.baidu
.com/s/1bpao02N
Connecting the two together is the address of the ROM
---------- Post added at 04:09 PM ---------- Previous post was at 03:59 PM ----------
I don't know how to upload pictures I use now is AEX the ROM also used his kernel fast charge as long as 1 hours or so WIFI and AEX the ROM supporting so can use WIFI but in other ROM do not use if you can help me to repair it will be a good kernel if you need the kernel add my QQ 371632477
Click to expand...
Click to collapse
Can someone translate it to English haha?

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I can't speak English, I'm sorry! I use translation software to translate my Chinese into English, if it has anything wrong, please forgive me. I am from China, a fast charging can work the kernel, here the author modifies it, to make it all work on ROM, I tested the fast charging kernel revised others, you can use AEX and DU. But there's no way WIFI doesn't work on other ROM

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Wilderone said:
That's an interesting question.
I always have known it to be:
>4100maH Battery
>Charging at 2A
Therefore:
4.1AH / 2A = 2.05 hours
Sent from my Redmi Note 4 using Tapatalk
Click to expand...
Click to collapse
I am so sorry to tell you, you forgot that the 2A are connected to 5V input -> 10W
The battery is a "BN41" with 4.4V and min 4.0Ah and 15.4Wh -> in theory 15.4Wh / 10W ~ 1.5h with a power factor of 100, but there will be loss as heat is generated during the charging. In order to charge the battery a BMS(either by the SoC or added circuit) is required, which will produce a loss of usable power, hence the higher charging time.
The out of the box charger of my Redmi Note 4 Global is a EU charger rated 5V 2A but never goes above ~1.3A+/-1% (meassured with a Keweisi KWS-10VA USB tester).
A 5V 1.5A USB(*1) and a 5V 8A USB(*6) power supply gives ~1.45A and my 5V3.1A car charger (2xUSB with alternating display for voltage, current and temperature) delivers a bit over 2A.
I read in reviews (cannot remember where) that the Xiaomi US charger for the Redmi 4x SD delivers a higher current, even when connected to 230V.