Galaxy S21 Ultra Battery Replacement: Cost & DIY Guide
A Galaxy S21 Ultra battery replacement costs about $79-99 at Samsung or a repair shop, but if you do it yourself the part is only $15-30. It's a DIY-doable job for a patient beginner, though the curved back glass and strong graphite adhesive make it a solid step up from an iPhone battery swap.
The S21 Ultra launched in early 2021, which puts most units in the 4-to-5-year window where the original cell has cycled past its useful life. If your once-all-day flagship now taps out by mid-afternoon, you're not imagining it, and you don't need a new $1,200 phone to fix it.
How to check your Galaxy S21 Ultra battery health
Samsung finally added a native battery health readout, and where you find it depends on your One UI version. On One UI 5 or newer (Android 13+), go to Settings → Battery and device care → Battery → Diagnostics. Under "Battery health" you'll see a plain-language grade: Good, Normal, or Weak. A "Weak" rating is Samsung's polite way of telling you the cell has degraded enough to warrant a replacement.
If you're still on an older One UI build, Samsung doesn't expose a battery percentage the way iPhones do. Rather than guess, install a free app like AccuBattery, which estimates your real-world capacity against the factory 5000mAh rating over a few charge cycles. Once it shows you're holding well under 80% of the original design capacity, that's your cue. You can also check Settings → Battery and device care → Battery → Usage since last full charge to see whether a specific app is the real culprit before you assume the hardware is done.
Signs your Galaxy S21 Ultra battery is failing
Battery wear rarely announces itself all at once. Watch for a cluster of these symptoms:
- Galaxy S21 Ultra battery draining fast even with light use, or dropping 20-30% overnight in standby.
- Sudden shutdowns at 20-40% remaining, especially in cold weather or when the camera or 120Hz display spikes demand.
- The phone runs hot during ordinary tasks, or charges much slower than it used to.
- Your Galaxy S21 Ultra battery not charging past a certain point, or the percentage jumping around erratically.
- The phone only stays on while plugged in.
Safety note: if you ever see the back glass lifting, a gap forming around the frame, or a screen that's started to bulge, stop using the phone. Those are signs of a swollen battery. A puffed lithium cell is a fire and rupture hazard, so don't puncture, bend, or squeeze it. Power the device down, keep it away from anything flammable, and replace the battery promptly rather than trickle-charging a swelling pack.
Galaxy S21 Ultra battery replacement cost
Here's what you can expect to pay in 2026 across the three main routes. The Galaxy S21 Ultra battery replacement cost swings widely depending on who does the labor.
| Option | Typical 2026 price | What you get |
|---|---|---|
| Samsung / uBreakiFix (authorized) | $79-99 | Genuine part, warranty on the repair, but appointment and wait times |
| Local repair shop | $50-80 | Same-day service, quality varies by shop |
| DIY (parts only) | $15-30 | Battery plus adhesive; you supply about an hour of patience |
The gap between the top and bottom row is almost entirely labor. Since the S21 Ultra opens from the back rather than the screen, the actual part is inexpensive; you're mostly paying a shop for the careful heat-and-pry work. If you're comfortable following steps and searching "Galaxy S21 Ultra battery replacement near me" mainly turns up $80+ quotes, the DIY route saves the most.
The exact replacement battery for the S21 Ultra
The S21 Ultra uses a 5000mAh lithium-ion pack, Samsung part number EB-BG998ABY. It fits every regional variant of the phone, sold as SM-G998, SM-G9980, SM-G998B, SM-G998N, SM-G998U, and SM-G998U1, so a US carrier model and an international dual-SIM unit take the same cell. When you shop for a Galaxy S21 Ultra OEM battery, match that 5000mAh rating and the EB-BG998ABY number and you're guaranteed the right fit.
You can browse compatible replacement cells in our replacement batteries collection. Because PhonePartPro sells retail and wholesale, buying a single battery still comes at parts-tier pricing rather than the marked-up rate a repair counter charges. Avoid the temptation of a no-name pack advertising more than 5000mAh; padded capacity claims usually mean a lower-grade cell that degrades faster.
Replacing it yourself: step overview and honest difficulty
Here's how to replace a Galaxy S21 Ultra battery at a high level. You'll want a heat source (hair dryer or heat pad), a suction cup, thin plastic picks, a small Phillips driver, and fresh adhesive strips.
- Heat the back glass evenly to soften the adhesive, then use a suction cup and pick to slice around the perimeter and lift the rear panel. Go slow near the fingerprint sensor and camera bump.
- Remove the charging-coil bracket and disconnect the battery connector first, before anything else, to kill power to the board.
- Release the old battery. S21 Ultra cells are held by strong pull-tabs and adhesive. Pull the tabs slowly and evenly; if they snap, apply a few drops of high-concentration isopropyl alcohol under the edges to break the bond. Never pry a swollen cell with metal.
- Seat the new 5000mAh battery, reconnect it, and test that the phone powers on before you re-seal.
- Re-adhere the back glass with new strips and press firmly for a few minutes.
Difficulty: moderate (about 6/10). The steps aren't complicated, but the S21 Ultra's curved glass back cracks easily if you rush the heating, and the wireless charging coil needs care on reassembly. Budget 45-60 minutes and don't attempt it on a table cluttered with tiny screws. If you've never opened a phone, this is a doable first project, just not a five-minute one.
After the swap: calibration and warnings
Unlike an iPhone, a Samsung phone won't throw a permanent "battery health servicing" flag at you, though on some builds you may briefly see a genuine-parts notification. The more important step is calibration. Once your new battery is in, run one full cycle: charge to 100%, use the phone until it shuts off on its own, then charge uninterrupted back to 100%. This resets the fuel gauge so the percentage readout tracks the new cell accurately, which fixes the random jumps a fresh battery sometimes shows in the first day.
After that, your on-screen battery estimate and the Battery health diagnostic will settle down and reflect the real capacity you just restored.
Repair vs. upgrade: a $25 fix or a new phone?
The S21 Ultra is still a capable phone in 2026: a 108MP camera, a gorgeous QHD+ 120Hz display, and plenty of horsepower for everyday use. The only thing genuinely worn out is a consumable part that costs less than a tank of gas. Spending $15-30 on a battery instead of $900+ on a new flagship is the clear financial call, and it keeps a perfectly good device out of the e-waste stream.
That's the whole idea behind repairing rather than replacing: a single degraded component shouldn't retire an otherwise excellent phone. Restore the Galaxy S21 Ultra battery life you had on day one, and you've extended the life of the device by another two or three years for the price of a phone case. For more model-specific guides, see our battery replacement by model hub.
FAQ
How much does a Galaxy S21 Ultra battery replacement cost?
Expect $79-99 at Samsung or an authorized shop, $50-80 at an independent repair store, or just $15-30 in parts if you replace it yourself. The battery itself is inexpensive; most of the cost at a shop is labor.
How do I replace a Galaxy S21 Ultra battery?
Heat and remove the back glass, disconnect the battery connector, release the old 5000mAh cell using its pull-tabs (or a little isopropyl alcohol to break the adhesive), seat the new battery, test that it powers on, and re-seal with fresh adhesive. Plan on 45-60 minutes.
Why is my Galaxy S21 Ultra battery draining fast?
After four to five years, the original cell has simply lost capacity. Rule out a rogue app under Settings → Battery and device care first, but if a "Weak" battery-health grade or an AccuBattery reading confirms real wear, a new battery restores the runtime.
What battery does the Galaxy S21 Ultra use?
A 5000mAh lithium-ion pack, Samsung part EB-BG998ABY. It fits all variants sold as SM-G998, SM-G9980, SM-G998B, SM-G998N, SM-G998U, and SM-G998U1.
Is it worth replacing the Galaxy S21 Ultra battery in 2026?
Yes. The S21 Ultra still handles modern apps and photography well, so a $15-30 battery is far cheaper than a new phone and keeps a capable device in service instead of the landfill.
Why is my Galaxy S21 Ultra 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.