For Samsung Galaxy S21 5G G991 Replacement Battery 4000mAh
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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
- Restores daily runtime: a fresh 4000mAh cell replaces a battery that has lost capacity with age.
- Exact fit for SM-G991B: OEM standard dimensions and connector, so no modification is needed.
- Ideal for repair shops: a dependable, low-cost part for everyday S21 battery replacements.
- Checked before it ships: each battery is tested before dispatch from Manchester.
- Extends the life of your phone: far cheaper than upgrading when the rest of the handset still works well.
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
Is this the right battery for my Galaxy S21?
Yes, if your model number is SM-G991B or another G991 variant. It does not fit the S21 Plus, S21 Ultra or S21 FE.
Can I replace the S21 battery myself?
Professional installation is recommended. Screens and small parts are delicate, so we recommend having this part fitted by a qualified repair technician. Damage caused during fitting is not a product fault.
Should I replace the back cover adhesive too?
Yes. Once opened, the old adhesive will not reseal properly, so fit a fresh adhesive to keep dust out and hold the cover flat.
How quickly will it ship?
Same day from Manchester when you order before 4pm, Monday to Friday.
