Samsung Galaxy S7 charging behaviour
🔋⚡ The following charging behavioural patterns have been examined on a Samsung Galaxy S7 Edge, but presumably apply to the following devices as well:
- Galaxy S6, S6 Edge, S8, S9
- Galaxy Note 5, S6 Edge Plus
- Galaxy Note 7, 8, 9
- Galaxy Note 4 (but the Note 4 charges with ~10W instead of 6W with screen turned on).
The Samsung Galaxy S7 ist able to charge at voltages up to 10.0 Volts, which is necessary for the 9 Volts required by Qualcomm Quick Charge 2.0.
Any manual input voltage between 4.5V and 10V is supported.
The current, at any input voltage, if not limited by other factors (e.g. full battery or too low input voltage) is usually 0.5 Ampère.
If the USB data lanes (D+ and D-) are shorted, it signals indefinite charging currents.
The highest charging current supported at any voltage is 1.8A.
Among several other devices, the Galaxy S7 contains crippleware to deliberately slow down charging during operation (i.e. while not powered off or in stand-by mode).
Usually, during fast charging (constant current stage) via Qualcomm Fast Charging 2.0, the charging wattage is 15 Watts from 9 Volts provided by the charger and 1.67 Ampère drawn by the device.
When turning on the screen (leaving stand-by mode), the total wattage throughput is limited to 6 Watts, which is 0.67A at 9V and 1.20A at 5V.
The wattage consumed by the device's components (display, CPU, GPU, etc.) is subtracted from the wattage that arrives to the battery, which means that, for example, when the device components use 2W, the battery only receives 4W.
While and shortly after booting, or when viewing the bootloader options, 1.8A are drawn at 9V temporarily, which means that the charging IC is able to request the elevated voltage (9V instead of 5V) independently from the operating system, and that the 6W power throughput throttling is caused by a software signal sent by the operating system to the charging controller, possibly into a system file located inside
/sys/class/power_supply/battery, deliberately requesting the strong reduction of charging current during operation of the device.
This limitation might discourage usage of the device while charging, and has been mocked by OnePlus, a mobile phone brand of Oppo, a competing vendor of mobile phones, in several Dash Charge commercial films.
Using the flashlight, Always-on display and Edge night clock features have no effect on the charging current, which means that the power throughput can still be 15 Watts with these features in operation.
Manually elevated voltage
When manually applying 9 volts to the USB port, e.g. using a bench power supply or a Qualcomm Quick Charge 2.0/3.0 Voltage tester through a two-port KW203 type USB multimeter, where port 1 has USB 2.0 data pins that pass through and port 2 has shorted data lanes, the device in stand-by mode charges with up to 12 Watts and up to 1.8A depending on input voltage, where decreasing the voltage from 9V increases the current anti-proportionally until reaching the 1.8A limit.
If a voltage drop is caused by the USB wire (e.g. when using a longer cable, causing a lower voltage to arrive at the phone's USB port), the current increases anti-proportionally to the voltage drop (up to 1.8A) if the voltage is manually applied, while a voltage drop while using 9 Volts (at charger) from Qualcomm Quick Charge 2.0 does not cause the current to increase beyond 1.67A, despite technically possible.
A possible reason for the latter behaviour could be that Samsung's precluded wall adapter, the EP-TA20EWE in Europe, officially only supports either 5V 2.0A or 9V 1.67A. According to tests, the wall adapter supports 9V 1.8A and starts dropping the output voltage when demanding more current, but the 1.8A at 9 Volts is possibly not sustainable at higher environmental temperatures to prevent overheating.
To prevent heat damage to the battery and other components, charging is limited to around 10 Watts above measured battery temperarures of 35°C, regardless of whether the device is turned on, in stand-by mode or powered off, which means that the charging wattage is controlled by the integrated charging controller (IC) instead of the software.
The 6W limitation however is engaged at any tempoerature, even at cold temperatures where the device could be charging at full throttle (15W) without limiting charging speed.
Unlike the S7 and other Samsung mobile phones listed above, some mobile phones subtract the power used by the device components from the total power throughput without reducing the total power throughput itself.
Some mobile phones such as the UleFone Armor 2 and presumably most laptop computers use the supreme charging method known as spare current, where usage of the device does not affect the wattage that arrives at the battery, because the additional power needed for the device's components during operation gets additionally drawn from the power supply.
- "Video of the OnePlus 5T charging with screen on, in comparison to the iPhone 8 Plus, Galaxy S8 Plus and Google Pixel 2 XL". 2017-11-23. Archived from the original on 2018-05-10. Retrieved 2020-08-25.
- "OnePlus 3T charging speed comparison with Google Pixel XL during commute in car (uploaded January 26th 2017)". 2017-01-26. Archived from the original on 2017-09-06. Retrieved 2020-08-25.
- Qualcomm QuickCharge 2.0 and 3.0 testing device (AliExpress item number 32830330713)