Phone charging current periodic

[chuping]

I recently noticed my S20 FE has a strange charging current fluctuating between 1.1A (10W) and 1.6A (15W). Not sure if anyone experienced the same with their Samsung 15W charger. You can download a battery monitoring app to check your current flow curve.

 

[chuping]

I went for servicing and they changed the charging port and battery. However, the charging current pattern is the same when the phone is powered off (up to 90%). The charging time is roughly 1min for 1% for battery level <90%. So is this the designed charging pattern of the phone?

 

[username03]

When the phone temperature is cool, it charges faster, when it’s warm, it’s deliberately slowed down to protect your phone battery and parts.

Above 80%, it will slow down even when it’s cool, aka trickle charging, to protect your battery from premature wear from fast charging.

 

[chuping]

When the phone temperature is cool, it charges faster, when it’s warm, it’s deliberately slowed down to protect your phone battery and parts.

Above 80%, it will slow down even when it’s cool, aka trickle charging, to protect your battery from premature wear from fast charging.

You are right. For my phone, I noticed that trickle charging happens at >87% (the current flow reduce gradually over time). At <=87%, the battery can charge at 15W if the battery is cooler at 30C, else it will still charge periodically between 10-15W.

I did more testing on the temperature (rough observation). Temperature is taken from CPU-Z and CpuFloat. The exact temperature that the condition applies might depend on CPU temperature also, no concrete evidence to support since I do see 45C CPU but still charging at 15W.

Conditions
1. <33C (but I usually observe my battery at 30C because of the A/C), the battery can charge at 15W regardless the phone is turned on or on standby (screen off).
2. 33C to 36C, the battery will charge periodically between 10W and 15W in standby, 6W when turned on. The period depends on the current temperature. i.e. the higher the temperature is, the longer it will stay at 10W.
3. >36C, the battery will charge at 10W when standby, 6W when turned on.

The case that I used to protect my phone does affect the temperature, but it is annoying to take it off every time I charge. So I guess I will let it rest on a heatsink while charging. The service centre should advise me on this so I don't have to experiment on it, but at least they did change the problematic USB-C port for me.

I can't find any online article documenting what method the phone used to charge slower to prevent overheating. All along I thought it will draw constant power depending on temperature, e.g. constant 13W for 34C. Since I have gotten the USB meter and saw that periodic current flow, I thought maybe my USB-C port is causing the problem (signal lost, need to renegotiate the power).

Hope whoever sees this post understand more about keeping your phone cool when charging, especially using a fast charger or wireless charger.

 

[keenklee]

I used to have a lot of interest in this area.
Now, I use the battery settings to disable Fast Charge on my Note10+ and charge it to about 85% in the hope that my battery will last.

Thank you for your interesting info.

 

[firesong]

To add, try not to use your phone while charging. For Android phones, I have friends who switch it off before slow charging. I do this myself too once in a while. If the over-charging protection works as intended, it shouldn't charge the battery once it hits 100%, so it's technically possible to do.

For the iPhone, the adaptive charging seems to work fairly well imo. If you have regular charging patterns (eg, charging overnight and waking and disconnecting the phone at the same time regularly), you'll find that it actually schedules the charging to just enough to give it a full charge, so it is delayed and timed to fully charge the phone by the time you disconnect. Realised this when I had to take the phone off the charger for a night emergency once, and it wasn't anywhere near fully charged.

 

[keenklee]

It is unfortunate that Samsung by default do not have this IOS feature.
The Samsung's Android don't even have the sleep function.
But it can be done using app with external hardware.