This Galaxy S21 how-to guide explains everything you need to know on how to charge Galaxy S21 battery properly. The two charging modes (USB cable, wireless charging) are explained and illustrated with detailed steps. Questions related to charging Galaxy S21 battery, including the first time charging, disabling fast charging, overnight charging, topping up the battery, draining up the battery, are answered.
All three Galaxy S21 models (Galaxy S21, S21+, and S21 Ultra) use identical battery and charging technology. So, this guide applies to all these 3 models.
Update: in the Android 14 (One UI 6) update for Galaxy S23, S22, and S21, the battery settings are separated from the Device Care.
Two charging modes to charge Galaxy S21 battery
You can charge Galaxy S21 battery in two different modes:
- USB cable charging.
- Wireless charging.
These two modes are based on different technologies. And there are different standards for these two charging methods.
USB cable charging
USB cable charging is common among smartphones. Almost all smartphones support USB cable charging.
But charging speed differs dramatically due to various charging protocols supported and wall chargers (adapters) used. Occasionally, even the USB cable may play a role.
Current smartphones support at least 5W USB charging. Of course, Galaxy S21 offers more features for battery charging.
Based on charging power, Galaxy S21 supports the following USB charging “protocols”:
- Normal USB charging (up to 5W). There are no requirements for the wall charger (adapter). You can also use any USB cables.
- Fast USB charging (up to 10W). You need a wall charger that supports 5V 2A output. Samsung shipped this type of wall charger with Galaxy S4 and S5. There is no requirement for a USB cable. But you need to make sure the USB has decent quality.
- Adaptive fast charging (up to 15W). Instead of adopting Qualcomm’s QC (Quick Charge)3.0/4.0, Samsung implemented its own proprietary adaptive fast charging. The wall charger needs to support both 5V/2A and 9V/1.67A output. Samsung shipped this type of adaptive fast charger with Galaxy S6, S7, S8, and S9.
- Super-fast charging (up to 25W). Galaxy S21 supports USB-C PD (Power Delivery) 3.0 up to 25W. Samsung called it superfast charging with their own PPS (Programmable Power Supply) profile implementation. You can find this type of charger in the box of Galaxy S10 and S20. To enjoy the super-fast charging, you MUST use a USB-C to C cable (like the one in Galaxy S21 box). If you use the USB-A to C cable, the maximum charging speed will decrease to 15W or even 10W.
Galaxy S21 backpedaled the 45W superfast charging on Galaxy S21. None of Galaxy S21, S21+, and S21 Ultra supports 45W super-fast charging. The maximum charging power for Galaxy S21 is 25W.
You may check this guide for a detailed explanation of adaptive fast charging and super-fast charging.
You can also charge Galaxy S21 battery wirelessly using a wireless charging pad.
Samsung started to offer wireless charging on Galaxy S6. Over the years, Samsung has improved it greatly.
Galaxy S21 supports the following three wireless charging “protocols”:
- Qi wireless standard charging (up to 5W). You can use any Qi wireless charger.
- Fast wireless charging (up to 7.5W). Galaxy S7, S8, and S9 support this type of wireless charging. Some third-party Qi wireless chargers may offer a similar charging speed. But the compatibility is not guaranteed. So, It is recommended to use Samsung’s fast wireless charger, like this one.
- Fast wireless charging 2.0 (up to 12W, typically 10W). Since Galaxy S10, Samsung updated its wireless charging technology with the wireless fast charging 2.0. You should get a Samsung wireless charger that supports fast wireless charging 2.0 (like this one) if you want to maximize the wireless charging speed for Galaxy S21 battery.
Please note the wireless charging pad usually is sold together with a wall charger(or an adapter) in the box. You should use the bundled wall charger for the wireless charging pad. Using other wall chargers or adapters may degrade the performance of the wireless charging.
Some official Galaxy S21 covers (e.g., Galaxy S21 Smart LED View Cover, Smart Clear View (S-View) Cover, and LED back cover) use NFC to communicate with the phone. These covers do NOT affect wireless charging on Galaxy S21.
Steps to charge Galaxy S21 battery through a USB cable
To charge Galaxy S21 battery through the USB port, you need the following:
- A wall (USB) charger. The wall charger will determine the maximum charging speed (power), as mentioned earlier. If you need to buy a new one, you should get one with a USB-C port.
- A USB cable. The USB cable must match the charger. As you charge Galaxy S21 battery through the USB port, you need to use the USB-C to C cable (in your Galaxy S21 box) if your charger has a USB port, or a USB-A to USB-C cable if your charger has a “bigger” normal USB port.
Anyway, quality matters. Never use low-quality cables or chargers. It is unwise to save $20 on essential accessories for an $800 phone.
Step 1: Connect the USB cable to the wall charger
You need to use a USB cable matching the port on the wall charger.
The USB-C cable in the Galaxy S21 box can be used if your wall charger has a USB-C port.
Step 2: Connect the USB cable to Galaxy S21
As shown below, you can plug the other end of the USB cable into the USB-C port at the bottom of the Galaxy S21.
You can only insert a USB-C connector into the port. If your USB cable is from USB-A to micro USB, you must get a micro USB to USB-C connector for the cable before inserting it into the USB-C port.
The USB-C connector is symmetric. So, it is not necessary to check the upside or the downside.
Step 3: Connect the charger to an electric socket (power on the wall charger)
Most wall chargers do not have a switch. To power on the wall charger, you simply connect it to an electric socket.
Step 4: Wait till Galaxy S21 is fully charged.
You should avoid using Galaxy S21 heavily (e.g., play games) when it is being charged.
If possible, you should let the battery be fully charged, although it is not required. Battery charging status is shown in the battery charging status icon in the status bar. On the lock screen, you can also find the charging status.
Please note 100% does not mean fully charged. You may still need to wait one or two minutes from 100% to fully charged.
If Protect battery is enabled (a new feature in the Android 12 update for Galaxy S21), Galaxy S21 will stop charging automatically once the battery level reaches 85%.
Step 5: Disconnect the USB cable from Galaxy S21
Once the Galaxy S21 battery is fully charged, you can disconnect the USB cable from the Galaxy S21, if it is convenient to do so.
Step 6: Power off the wall charger
Wall chargers are not able to turn off themselves automatically. It is better to unplug the wall charger or shut off the power supply to the charger if it is convenient to do so.
Steps to charge Galaxy S21 battery through a wireless charging pad
To charge Galaxy S21 battery wirelessly, you only need a wireless charging pad (with a power adapter). You may check this wireless charger guide on how to choose a wireless charger for your Galaxy S21.
Currently, most wireless chargers are designed with two parts:
- A power adapter (or a wall charger).
- One or more wireless charging pads.
If the power adapter is detachable, it usually uses a USB cable to connect to the charging pad.
Step 1: Connect the power adapter (or USB wall charger) to the wireless charging pad
You need to use the bundled power adapter/wall charger to power the wireless charging pad. If the power adapter is detachable, you need to connect it to the charging pad with the bundled cable.
Normally, you should not replace the bundled adapter (or USB charger) with other USB chargers. Some adapters or USB chargers are specially designed to power the wireless charging pad.
Step 2: Power on the wireless charging pad
For most wireless chargers, you can connect the power adapter (wall charger) to an electric socket to power on the wireless charging pad.
Wireless charging pads usually have one or more LEDs indicating the status of the pad. You need to make sure the wireless charging pad is ready.
Step 3: Place Galaxy S21 in the wireless charging pad
You need to place Galaxy S21 in the centre of the wireless charging pad, as shown below.
You should try to align the centre of the charging pad with the wireless charging coil on Galaxy S21 so that it charges Galaxy S21 battery at its fast speed and with minimum energy loss.
Step 4: Wait till Galaxy S21 is fully charged.
You can let Galaxy S21 sit on the charging pad until it is fully used.
Of course, you can use the phone if you need to. But it is not recommended to use the phone heavily when it is being charged (on the charging pad).
If Protect battery is enabled, Galaxy S21 will stop charging automatically once the battery level reaches 85%.
Step 5: Remove Galaxy S21 from the charging pad
Once the Galaxy S21 battery is fully charged, the wireless charging pad will shut off the power supply to the phone automatically. And it will NOT charge the phone again unless you remove and put back the phone.
So, if you use wireless charging to charge Galaxy S21 battery overnight, you may find the battery level is not 100% the next morning. This is normal.
Should I charge Galaxy S21 battery for 8 hours first time?
No, when Galaxy S21 leaves the factory, the battery is partially charged. You should be able to use the phone without charging.
Normally, for a new Galaxy S21, the battery level should be around 40-65%, depending on the shelf life.
Charging a new battery for 8 hours is not applicable to Galaxy S21. Actually, it is not applicable to most Li-ion batteries nowadays.
Should I disable fast charging and fast wireless charging on Galaxy S21?
Generally, it is NOT recommended to disable fast charging and fast wireless charging on Galaxy S21.
Heat is the enemy of Galaxy S21 battery. Fast charging always generates more heat during the charging process. But you should not worry about the heat.
The charging control unit in the Galaxy S21 can regulate the charging power (current and voltage) based on the battery temperature. So, the battery is always operating in the designed range. Galaxy S21 can even turn off the system if the battery temperature is too high.
Of course, if you charge Galaxy S21 battery at a slower speed, the heat generation rate will be lower. This may slightly slow down the degradation process of the Galaxy S21 battery. But the gain is marginal.
If you want, you can disable fast charging, superfast charging, and fast wireless charging.
In the Device Care page, as shown above, tap Battery to access battery usage details and battery settings.
You can find a lot of informational settings on the Galaxy S21 battery on the Battery settings page, including:
- Battery usage.
- Estimated battery life.
- Power saving mode.
- Background usage limits.
- Wireless power sharing.
- More battery settings.
As shown below, you can scroll down and tap More battery settings.
On the More battery settings page, as shown above, you can find the charging category.
You can use the switch to enable or disable fast charging, super fast charging, and fast wireless charging individually, based on your needs.
Typical charging time for Galaxy S21
With Samsung’s 25W super-fast charger (which was bundled with Galaxy S20; you can buy it from local Samsung Store or Amazon), the typical charging time (from less than 5% to 100%) is:
- Galaxy S21: about 70-80mins.
- Galaxy S21+, about 70-80 mins.
- Galaxy S21 Ultra, about 65-75 mins.
So, with the same charger, the charging time for these 3 models of Galaxy S21 actually is very close although Galaxy the battery capacity varies from 5000mAh (Galaxy S21 Ultra) to 4000mAh (Galaxy S21). This suggests Galaxy S21 Ultra can draw more power from the charger than Galaxy S21 (and S21+) with the same charger.
FAQs for charging Galaxy S21 battery to prolong the battery life
Here are some frequently encountered questions on how to charge Galaxy S21 battery to slow down the degradation of Galaxy S21 battery.
Q1: Is it safe to charge S21 battery overnight?
A1: Yes, it is safe. It is not necessary to get up in the wee hours to unplug the charger.
Of course, it is a good habit to disconnect the charger once the phone is fully charged only if it is convenient to do so.
For USB charging, the trickling current will NOT damage the battery or affect the lifespan of the battery noticeably.
For wireless charging, the wireless charger will shut off the power output automatically when the phone is fully charged. So, you should never worry about leave Galaxy S21 on the wireless charging pad overnight. If you often charge Galaxy S21 battery overnight with a wireless charging pad, you may even disable fast wireless charging, as discussed earlier.
Q2: Should I stop charging the battery when it reaches 70-80%?
A2: No, you should try to charge the battery to fully charged if possible.
Some experts (btw, there some so many such experts) claimed it could extend the lifespan of the battery if you charge it to 70-80% (not full). This is nonsense. There is no scientific research supporting this claim. The cited research is for ancient batteries.
Q3: Should I drain the battery completely periodically (monthly, quarterly…)?
A3: No, it is NOT necessary to drain the Galaxy S21 battery completely.
The old-school textbook taught this technique for ancient batteries to help with battery calibration. But for the current smartphone battery, it is not needed. The sensors inside the battery and phone can gauge the battery level accurately without relying on the point of 0%.
In fact, you should try to avoid such a battery drain. If you frequently let the battery drain completely, it is harmful to many electrical components and sensors inside the Galaxy S21. Most of the time, Galaxy S21 will shut itself off to protect the phone.
Q4: Should I top up Galaxy S21 battery to 100% whenever possible?
A4: No, you should not. It may create unnecessary wear on the battery.
You should charge Galaxy S21 battery only when you need to. You can estimate whether the battery is enough before you can reaccess the charger.
Q5: Can I use the phone when I charge Galaxy S21 battery?
A4: Yes, you can. It will only slow down the charging.
Of course, it is NOT recommended to use the phone heavily (e.g., play games) when it is being charged.
A1: Yes, you can use Wireless PowerShare and Galaxy S21 battery through USB charging concurrently
Obviously, you cannot use wireless PowerShare when charging Galaxy S21 through wireless charging.
Also, if you are using a back cover (e.g., Galaxy S21 LED back cover) or a flip cover (e.g., Galaxy S21 Smart LED View Cover or Galaxy S21 Smart Clear View Cover (S-View Flip Cover), you may need to remove the case or cover to use Wireless PowerShare to charge other devices.
Q7: What is Protect Battery option? Should I enable it?
If enabled, Galaxy S21 will limit the charging capacity to 85% of the full capacity to reduce the charging wear. In other words, Galaxy S21 will stop charging once the battery level reaches 85%.
You may enable Protect Battery to prolong the battery life span if you have no problems accessing a charger when you need it, as explained here.
Do you have any questions on how to properly charge Galaxy S21 battery for Galaxy S21, S21+, and S21 Ultra?
If you have any questions about charging Galaxy S21 battery, please let us know in the comments.
The community will help you.
If you have any questions about using Galaxy S21, you may check our detailed step-by-step Galaxy S21 guides:
- Galaxy S21 new features guides.
- Galaxy S21 how-to guides.
- Galaxy S21 camera guides.
- Galaxy S21 accessories guides.
You can also post questions or share your thoughts on our Facebook page.
The official Samsung Galaxy S21 user manual (PDF) in your local language can be read and downloaded here.
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Enjoy your Galaxy S21.