For Samsung Galaxy S21 5G G991 Replacement Battery 4000mAh The Repair Plus
In stock
Discount applies at checkout on any mix of parts — ideal for repair shops.
Estimated delivery · Royal Mail Tracked 482–3 working days
- Order placedToday
- DispatchedSame day
- At your door2–3 days
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Phone parts are delicate. We recommend fitting by a qualified repair technician — damage caused during fitting is not a product fault. Need help choosing the right part? Call 07425 443625 or email info@therepairplus.com (Mon–Fri 10:00–18:00). Repair shop? Open a trade account.
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The Repair Plus Samsung Galaxy S21 5G 4000mAh replacement battery is a brand new internal battery for the Galaxy S21 (SM-G991B) that fixes fast drain, sudden shutdowns and a phone that no longer lasts the day. Built to OEM standard fit and connector layout, it is tested before dispatch and shipped the same day from Manchester when you order before 4pm, Monday to Friday.
Key features
- 4000mAh capacity: brings back all-day battery life for calls, maps, streaming and photos.
- Built-in protection: protection circuitry guards against overcharging, overheating and short circuits.
- Made for the G991 only: OEM standard size and flex connector for a clean, straight fit.
- Stops worn-cell faults: ends random shutdowns, swelling-related lifting and constant trips to the charger.
- Tested before dispatch: every battery is checked before it ships.
Specifications
| Part | Internal replacement battery |
|---|---|
| Capacity | 4000mAh |
| Compatible model | Samsung Galaxy S21 5G (SM-G991B) |
| Condition | Brand new |
| Quality | OEM standard |
| Dispatch | Same day before 4pm, Monday to Friday, from Manchester, UK |
| Returns | 30 days |
Compatibility
Fits the Samsung Galaxy S21 5G (SM-G991B and other G991 variants) only. It does not fit the Galaxy S21 Plus (SM-G996B), Galaxy S21 Ultra (SM-G998B) or Galaxy S21 FE (SM-G990B), which each use a differently sized battery. Check your model number in Settings > About phone before ordering; the model number is listed near the top of that screen.
What you need to fit it
Replacing the battery means removing the back cover first. You will need a heat pad or heat gun, a suction cup, plastic opening picks, a small Phillips screwdriver, battery adhesive strips or a battery removal solution, and a new back cover adhesive to reseal the phone. Disconnect the battery flex before lifting the old cell, and never bend or puncture a lithium battery. Once the phone is sealed, charge it fully and use it normally for a few cycles so the battery reading settles.
Why buy from The Repair Plus
- Same-day dispatch when you order before 4pm, Monday to Friday.
- UK stock, shipped from Manchester.
- Every part tested before dispatch.
- 30-day returns.
- Trusted by DIY repairers and independent repair shops.
Frequently asked questions
Will this battery fit a Galaxy S21 Ultra?
No. The Galaxy S21 Ultra uses a larger 5000mAh battery. This one fits the standard Galaxy S21 5G only.
Does it support fast charging?
Yes. Charging speed is controlled by the phone and charger, and this battery works with your S21's normal charging, including fast charging.
How do I know my battery needs replacing?
Common signs are the phone dying well before 0 percent, needing charging several times a day, running hot, or the back cover lifting from a swollen battery.
When will my order be dispatched?
Order before 4pm, Monday to Friday, and we dispatch the same day from Manchester.
