Galaxy S21 Battery Replacement: Cost & DIY Guide
A Galaxy S21 battery replacement costs around $79-99 at Samsung or a repair shop, but the part alone is just $15-30 if you replace it yourself. It's a DIY-doable job for a patient first-timer, and the S21's 4000mAh cell is one of the more approachable Samsung batteries to swap.
The standard S21 arrived in January 2021, which means most units are now four to five years into service, right in the window where the original battery has cycled past its useful capacity. If your S21 used to comfortably reach bedtime and now begs for a charger by afternoon, the battery is the worn part, not the phone.
How to check your Galaxy S21 battery health
Samsung ships a native battery health readout, and where you find it depends on your One UI version. On One UI 5 or newer (Android 13+), head to Settings → Battery and device care → Battery → Diagnostics and read the "Battery health" line, shown as a plain grade: Good, Normal, or Weak. A "Weak" grade is Samsung telling you the cell has degraded enough that a replacement makes sense.
If your S21 is still on an older One UI build, Samsung doesn't expose a battery percentage, so don't guess at it. A free app such as AccuBattery estimates your actual capacity against the factory 4000mAh rating over several charge cycles. When it shows you're holding well under 80% of that original figure, the cell is spent. It's also smart to open Battery → Usage since last full charge first, to confirm that a hungry background app isn't the real cause before you decide the hardware is done.
Signs your Galaxy S21 battery is failing
Wear usually shows up as several small annoyances rather than one clean failure:
- Galaxy S21 battery draining fast under normal use, or steep overnight drain in standby.
- Random shutdowns while 20-40% still shows, especially when it's cold out.
- The phone warms up during light tasks and charges slower than it once did.
- A Galaxy S21 battery not charging consistently, or a percentage that jumps around.
- It only stays powered on while plugged in.
Safety note: the S21's back is Samsung's "Glasstic" polycarbonate rather than glass, but a swelling battery will still bow it outward or lift the flat 6.2-inch display at an edge. If you see that, stop using the phone. A puffed lithium cell is a fire and rupture risk, so never puncture, bend, or press on it. Power down, keep it away from anything flammable, and replace the battery promptly rather than continuing to charge a swollen pack.
Galaxy S21 battery replacement cost
Here's what to budget in 2026. The Galaxy S21 battery replacement cost comes down mostly to labor, because the cell is cheap.
| Option | Typical 2026 price | What you get |
|---|---|---|
| Samsung / uBreakiFix (authorized) | $79-99 | Genuine cell and a repair warranty, but appointments and wait times |
| Local repair shop | $50-80 | Frequently same-day, though results vary by shop |
| DIY (parts only) | $15-30 | Battery plus adhesive, and about an hour of your time |
The spread between the top and bottom rows is nearly all labor. Because the S21 opens from the back and the part is inexpensive, doing it yourself is where the real savings are. If a search for "Galaxy S21 battery replacement near me" keeps returning $80-plus quotes, the DIY route trims that to the cost of the battery and a strip of adhesive.
The exact replacement battery for the S21
The standard S21 uses a 4000mAh lithium-ion battery, Samsung part number EB-BG991ABY. That's a smaller cell than the S21 Plus (4800mAh) or the Ultra (5000mAh), so make sure you're matching the base model. The EB-BG991ABY fits every regional variant, sold as SM-G991, SM-G9910, SM-G991B, SM-G991BDS, SM-G991F, and SM-G991N. When shopping for a Galaxy S21 OEM battery, confirm both the 4000mAh rating and that part number to be sure you have the right cell.
You can buy the correct cell directly from our Galaxy S21 5G replacement battery listing, or browse the full replacement batteries collection for related parts. Because PhonePartPro sells retail and wholesale, a single battery is priced at parts level rather than the marked-up rate a repair counter charges. Ignore listings that advertise more than 4000mAh; padded capacity claims usually point to a lower-grade cell that fades faster.
Replacing it yourself: step overview and honest difficulty
Here's how to replace a Galaxy S21 battery at a high level. Line up a hair dryer or heat pad, a suction cup, thin plastic picks, a small Phillips driver, and fresh adhesive strips.
- Warm the back panel evenly to soften the adhesive, then use a suction cup and pick to slice around the edge and lift the rear cover.
- Remove the wireless-charging coil bracket and disconnect the battery connector first, before anything else, to cut power to the board.
- Release the old battery. The S21 cell is held by pull-tabs and adhesive. Pull the tabs slowly and evenly; if one snaps, apply a little high-strength isopropyl alcohol under the edges to break the bond. Never pry a swollen cell with metal.
- Seat the new 4000mAh battery, reconnect it, and check that the phone powers on before you re-seal.
- Re-adhere the back panel with new strips and press firmly for a few minutes.
Difficulty: moderate (about 5/10). The S21 is the friendliest of the three to open: its back is flat and the polycarbonate panel is less likely to crack than the glass on the Plus and Ultra. It's still glued and takes patience, so give yourself 40-60 minutes at a clear, well-lit workspace. For a careful beginner, it's a very reasonable first repair.
After the swap: calibration and warnings
A Samsung phone won't stamp your S21 with a permanent battery-servicing flag the way an iPhone would, though some software builds briefly show a genuine-parts notice. The step that matters is calibration. With the new battery in, charge to 100%, run the phone down until it shuts off on its own, then charge uninterrupted back to full. That resets the fuel gauge so the percentage tracks the new cell accurately and clears up the erratic readings a fresh battery sometimes shows in the first day.
Once it's calibrated, the on-screen estimate and the Battery health diagnostic will settle and reflect the real capacity you've just restored.
Repair vs. upgrade: a cheap part or a new phone?
The S21 remains a perfectly good daily driver in 2026, with a crisp 120Hz display, solid cameras, and enough performance for everyday apps. The single component that genuinely wears out is a consumable cell costing less than a couple of coffees. Spending $15-30 on a battery instead of $700-plus on a new phone is the obvious call, and it keeps a working device out of the e-waste stream.
That's the heart of repairing rather than replacing: one tired part shouldn't retire an otherwise capable phone. Bring back the Galaxy S21 battery life you had on day one and you extend the phone's useful life by another two or three years for the price of a case. For more model-by-model guides, visit our battery replacement by model hub.
FAQ
How much does a Galaxy S21 battery replacement cost?
About $79-99 at Samsung or an authorized shop, $50-80 at an independent store, or just $15-30 in parts if you replace it yourself. The battery is inexpensive; a shop's price is mostly labor.
How do I replace a Galaxy S21 battery?
Heat and remove the back panel, disconnect the battery connector, release the old 4000mAh cell with its pull-tabs (or isopropyl alcohol to break the adhesive), install the new battery, confirm it powers on, and reseal with fresh adhesive. Plan on 40-60 minutes.
Why is my Galaxy S21 battery draining fast?
After four to five years the original cell has lost capacity. Check for a rogue app under Settings, Battery and device care first, but if a "Weak" health grade or an AccuBattery reading confirms wear, a new battery restores the runtime.
What battery does the Galaxy S21 use?
A 4000mAh lithium-ion pack, Samsung part EB-BG991ABY. It fits variants sold as SM-G991, SM-G9910, SM-G991B, SM-G991BDS, SM-G991F, and SM-G991N. It is a smaller cell than the S21 Plus or Ultra.
Is it worth replacing the Galaxy S21 battery in 2026?
Yes. The S21 still handles modern apps well, so a $15-30 battery is far cheaper than a new phone and keeps a capable device in use instead of the landfill.
Why is my Galaxy S21 not charging?
First try a different cable and clean the USB-C port, since lint is a common cause. If it still won't charge or holds a charge poorly, a worn or swollen battery is the likely fault and should be replaced right away.