For Samsung Galaxy S21 3880mAh EB-BG991ABY Battery Replacement

Is your Samsung Galaxy S21 no longer holding a charge like it used to? Does your phone shut down unexpectedly even when the battery indicator shows power remaining, or do you find yourself reaching for the charger more and more frequently throughout the day? This 3880mAh EB-BG991ABY Replacement Battery is the exact high-performance component you need to restore reliable power delivery and extend the life of your flagship device. Available now at THE REPAIR PLUS, your trusted UK-based online store for quality phone repair parts.

Compatibility

This replacement battery is designed for the Samsung Galaxy S21 5G. According to multiple supplier listings and certification data, it is compatible with the following model numbers :

• SM-G991B (International/Global)

• SM-G991B/DS (Dual SIM)

• SM-G991U (US)

• SM-G991U1 (US Unlocked)

• SM-G991W (Canada)

• SM-G991N (Korea)

• SM-G9910 (China)

• SM-G991Q

The battery carries the original Samsung part number EB-BG991ABY with OEM reference GH82-24537A . According to certification body leaks, the Samsung Galaxy S21 was certified with a 3880mAh battery manufactured by Ningde Amperex Technology Limited .

Please verify your device model number in Settings → About Phone before purchasing to ensure correct fitment. THE REPAIR PLUS recommends double-checking your device compatibility to guarantee a perfect match.

Signs You Need This Replacement

• The time between charges is getting shorter and shorter, requiring multiple charges daily

• Your Galaxy S21 shuts down unexpectedly at a certain battery percentage (often 15-30%)

• The charging process completes surprisingly quickly, but the battery drains just as fast

• The battery is swollen or bulging, potentially pushing the screen or back cover apart—if swollen, handle with extreme caution

• You're experiencing overheating issues during charging or normal use

• The phone takes an unusually long time to charge, or the charging percentage jumps erratically

• Your device powers off immediately when unplugged, even showing a high percentage

Premium Quality Specifications

This high-quality replacement battery meets or exceeds the original EB-BG991ABY specifications. Please note that different suppliers offer various capacity ratings :

• Standard Capacity: 3880mAh (15.06Wh) 

• Alternative Capacity: Some suppliers rate at 4000mAh 

• Battery Type: Premium Lithium-Ion (Li-ion) / Lithium Polymer (Li-Po) 

• Voltage: 3.85V - 3.88V (standard) / 4.4V (maximum) 

• Model Number: EB-BG991ABY compatible

• Condition: Brand New with zero operating cycles 

• Safety Features: Built-in intelligent IC chip technology with protection against overcharging, overheating, overvoltage, short circuits, and over-discharge

• Compatible Phones: Samsung Galaxy S21 5G SM-G991 series 

Quality and Performance Notes

It is important to understand that aftermarket replacement batteries may have slightly different performance characteristics compared to the original factory battery. Some customer reviews indicate :

• Capacity Variation: One verified purchaser reported the actual capacity measured 3700mAh versus the advertised 4200mAh, approximately 12% less than claimed 

• Performance Expectations: While some users report excellent results ("battery holds great, thanks!"), others note disappointing battery life compared to expectations 

• Quality Consistency: Premium brands like GLK-Technologies use high-quality raw materials from South Korea 

What This Replacement Restores

• Original Battery Life: Restores the all-day performance your device had when new, providing extended power for 5G connectivity, media consumption, and daily tasks

• Reliable Power Delivery: Eliminates unexpected shutdowns and erratic battery behaviour

• Safe Operation: Premium quality batteries feature built-in protection against overcharging, overheating, and short circuits to ensure long-term use

• Device Integrity: Replacing a swollen battery prevents further damage to other internal components

• Sustainable Solution: Extend the life of your current device instead of contributing to electronic waste

Complete Toolkit Options

Several EB-BG991ABY replacement batteries come with comprehensive professional repair tools to assist with installation :

• Replacement battery (3880mAh or 4000mAh depending on supplier)

• Complete toolkit including:

  • Cross screwdriver

  • Tri-point Y screwdriver

  • 5-star Torx (pentalobe) screwdriver

  • Torx T5 and T6 screwdrivers

  • Curved tweezers

  • Opening tools (lever/scraper)

  • Opening picks

  • Suction cup

  • Adhesive strips for battery and back cover 

Some suppliers include installation tools , while others note explicitly that the package does not contain an installation kit . Please verify the specific contents of your chosen listing.

Important Battery Information

First-Time Use and Conditioning:

New Lithium-Ion batteries require proper conditioning to achieve optimal performance :

• New Lithium Ion batteries must be FULLY CHARGED and FULLY DISCHARGED 2 to 3 times before being FULLY CONDITIONED

• Full performance and longevity is only achieved after 2 to 3 complete charge and discharge cycles

• After you go through 2 to 3 cycles, you'll never have to condition your battery again!

• Please remember that a new Lithium-Ion battery's full performance and longevity is only achieved after 2 to 3 complete charge and discharge cycles 

Proper Charging Habits:

• Use the original charger that came with your device for best performance (25W fast charging compatible)

• Do not use low-quality third-party adapter chargers to charge your device as they will shorten battery life 

• To prolong battery lifespan, charge when the level drops to 20-30% rather than letting it drain completely to 0%

• All talk and standby times are approximate, depending upon carrier's network settings, signal strength, and features selected 

Installation Requirements :

• Professional installation by a qualified technician is strongly recommended

• We recommend installation by a specialist technician 

• Highly recommend professional installation; novices need the guidance of a professional 

• If using new battery the phone cannot be turned on, you may need to install it again and check that the cable is properly connected 

• Check if there is any dust in the connector or if any pin is broken before installation

• Make sure that the plug is properly connected to your device during installation

• Use ESD (electrostatic discharge) protection

Warranty Information:

• Many premium batteries come with warranty coverage (typically 30-day refund, 90-day replacement) 

• Contact the seller directly for specific warranty information 

Storage Guidelines:

• If storing for extended periods, maintain approximately 25-50% charge in a cool, dry place

• Capacity loss is minimal under proper storage conditions

Swollen Battery Warning:

If your old battery is swollen, handle with extreme caution. Do not puncture, crush, or apply heat—this can cause fire or explosion. Properly dispose of swollen batteries at authorised recycling centres.

Proper Disposal:

Never throw lithium-ion batteries in household trash. Always recycle through authorised electronic waste recycling centres. Tape over the terminals before disposal to prevent short circuits.

Important Safety Notice

⚠️ This is an intermediate-level repair requiring careful attention. One user reported a severe issue: "2 hours after installation, a black screen suddenly occurred, which has never happened to me before. The display unit of my S21 is definitely dead. Probably a short circuit due to insufficient battery performance" . The reviewer cautioned: "Be careful, it's not worth risking your phone for €10" .

THE REPAIR PLUS strongly recommends having this component installed by a qualified technician with experience in smartphone repairs. We are not responsible for any damage caused during installation .

Package Includes

1 x EB-BG991ABY 3880mAh Replacement Battery for Samsung Galaxy S21 5G