Apple Watch Series 5 & SE Battery A2277 / A2181 | 40mm 245mAh & 44mm 296mAh Replacement for MKNC2LL/A Models
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✅ Fits Apple Watch Series 5 (40mm & 44mm) and Apple Watch SE 1st Gen (2020, 40mm & 44mm) — P/N A2277 (40mm, 245mAh) and A2181 (44mm, 296mAh)
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✅ Precision-spec’d cells: ±0.1mm dimensional tolerance — critical for OLED-safe installation without display heat damage
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✅ Supports full ECG, blood oxygen, and heart rate sensor functionality post-replacement; no sensor calibration errors
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✅ Factory direct — both size variants available; custom labeling from 200 pcs; 12-month warranty; DOA < 0.3%
Product Description
Apple Watch battery replacement is technically different from iPad or iPhone battery work — and the margin for error is smaller. The Apple Watch Series 5 and Apple Watch SE share the same battery architecture across both the 40mm and 44mm variants. The 40mm uses P/N A2277 at 245mAh / 3.82V; the 44mm uses A2181 at 296mAh / 3.82V. Both are single-cell Li-Polymer designs in compact form factors where dimensional tolerance is a direct safety variable.
The Watch display is OLED, adhered to the case with heat-activated adhesive. To access the battery, a repair technician must apply heat (typically 70–80°C) to soften that adhesive before separating the display. A battery that is even 0.15mm thicker than spec will prevent the display from re-seating flush after replacement — causing either a visible gap, sensor contact failure, or permanent display damage if forced. Our cells are manufactured to ±0.1mm dimensional tolerance. This is not a marketing claim — it’s a measurable production spec that determines whether a Watch repair ends cleanly or generates a comeback.
Verified Compatible Models:
| Device | Size | Apple Model IDs | Battery P/N | Capacity |
|---|---|---|---|---|
| Apple Watch Series 5 | 40mm | A2092, A2157 | A2277 | 245mAh |
| Apple Watch Series 5 | 44mm | A2093, A2094, A2156 | A2181 | 296mAh |
| Apple Watch SE (1st Gen, 2020) | 40mm | A2351, A2352 | A2277 | 245mAh |
| Apple Watch SE (1st Gen, 2020) | 44mm | A2353, A2354 | A2181 | 296mAh |
⚠️ Not compatible with Apple Watch SE 2nd Gen (2022) — different battery P/N. Not compatible with Series 4 — while the form factor is similar, Series 4 uses A1975 (40mm) and A1976 (44mm), different P/Ns. Always verify the exact Watch model number before ordering.
Technical Parameters
| Parameter | 40mm (A2277) | 44mm (A2181) |
|---|---|---|
| Battery P/N | A2277 | A2181 |
| Compatible Devices | Watch S5 40mm, Watch SE 40mm | Watch S5 44mm, Watch SE 44mm |
| Nominal Voltage | 3.82V | 3.82V |
| Capacity | 245mAh | 296mAh |
| Cell Type | Li-ion Polymer soft-pack (Grade A) | |
| Dimensional Tolerance | ±0.1mm (critical for OLED re-seating) | |
| Charge Voltage (Max) | 4.35V ± 0.05V | |
| Discharge Cut-off | 2.75V | |
| Cycle Life | ≥ 600 cycles @ 80% DOD | |
| Operating Temperature | 0°C ~ 45°C (charge) / -20°C ~ 60°C (discharge) | |
| Connector Type | OEM-compatible flex connector | |
| Protection (PCM) | Overcharge / over-discharge / short circuit | |
| Sensor Compatibility | ECG, heart rate, blood oxygen — full function preserved | |
| Certifications | CE, FCC, RoHS, UN38.3; MSDS/SDS on request | |
| OEM/ODM | Custom label / packaging from 200 pcs per variant | |
| Condition | Brand new, 0 cycle, 100% capacity-tested | |
| Warranty | 12 months from shipment date | |
| MOQ | 50 pcs per variant (mixed orders accepted) | |
| Lead Time (Stock) | 3–5 business days | |
Need a stable supply plan? Send your model list + quantities + destination. We’ll confirm lead time, shipping method, and compliance documents before you place the order.
Features & Advantages
✅ 📐 ±0.1mm Dimensional Tolerance — OLED Display Protection
The Watch housing leaves virtually no clearance for thickness variance. An oversized cell prevents the OLED display from re-seating, which either cracks the display under pressure or leaves a visible gap that fails water resistance. Repair shops generating OLED damage complaints on Watch battery replacements are almost always using out-of-tolerance cells. Our ±0.1mm spec is held across production batches — not just first-article samples.
✅ ❤️ Full Sensor Functionality Preserved Post-Replacement
Apple Watch S5 and SE include ECG, heart rate, and blood oxygen sensors. These sensors do not require battery calibration, but they do require the battery to make correct electrical contact with the Watch main board after installation. Dimensional accuracy and connector seating are the variables. Our cells fit correctly — no sensor errors, no “ECG unavailable” warnings post-replacement.
✅ 🔋 Both Size Variants Stocked — 40mm and 44mm
A2277 (245mAh, 40mm) and A2181 (296mAh, 44mm) are stocked as separate SKUs but available in a single order. Repair distributors serving shops that handle both Watch sizes can fulfill from one supplier and one shipment without split MOQ requirements.
✅ 🏭 Custom Labeling and Retail Packaging from 200 pcs
Private label on the cell and branded retail packaging available from 200 pcs per variant. For repair distributors building branded smartwatch repair kit product lines, the S5/SE battery is one of the higher-volume Watch battery SKUs currently in the repair market.
Packing & Delivery
Lead Time & Shipping
In-stock items: Ship within 3 days
For standard replacement models with available inventory.Mass production orders: Ship within 7 days
For regular models under confirmed specifications and packaging requirements.Customized orders: Ship within 15 days
For custom cell configuration, size, wire/connector, PCB/BMS, labeling, or packaging.
Note: Final dispatch time depends on total quantity, model complexity, packaging requirements, and shipping compliance documents. We will confirm the estimated shipping date (ETD) after order confirmation.
Air freight (urgent, smaller volume)
Sea freight (cost-effective for bulk)
Rail / Truck (subject to destination)
Express channels
Documents available: UN38.3 / MSDS / Transport Test Report (if applicable)
Compliant packaging and carton labeling can be arranged based on the chosen shipping method.
EXW / FOB / CIF / DDP available
One-Stop Sourcing for the Complete Apple Ecosystem
-Streamline your supply chain. Consolidate your MacBook, iPad, iPhone, and Watch battery orders into a single shipment to reduce logistics costs and maximize your wholesale margins.
FAQ
Q1: Does the A2277/A2181 battery fit both Apple Watch Series 5 and Apple Watch SE?
A: Yes. Apple Watch Series 5 (40mm) and Apple Watch SE 1st generation (2020, 40mm) share battery P/N A2277 (245mAh). The 44mm variants of both devices share A2181 (296mAh). Not compatible with Apple Watch SE 2nd Gen (2022) — different P/N. Not compatible with Series 4 despite the similar chassis — Series 4 uses A1975/A1976. Always confirm the exact Watch model number, not just the case size, before ordering.
Q2: Why is dimensional tolerance specifically critical for Apple Watch battery replacement — more so than for iPhone or iPad?
A: The Watch housing has almost no clearance margin between the battery and the OLED display assembly. A cell that is 0.15–0.2mm thicker than spec creates enough pressure during reassembly to crack the OLED, delaminate the display, or prevent the crown seal from engaging correctly. Unlike iPhones where a slightly thicker battery might just bow the back cover, the Watch enclosure is rigid metal with no flex tolerance. This is why Watch repairs have a higher damage rate with out-of-tolerance aftermarket cells. Dimensional precision is the primary quality variable for this SKU — not capacity.
Q3: Will ECG and blood oxygen sensors work normally after replacing the Apple Watch S5 battery?
A: Yes, when the battery is installed correctly. ECG, heart rate, and SpO2 sensors do not communicate through the battery — they operate via the Watch’s main board and back glass sensor array. What can cause sensor errors post-replacement is incorrect battery seating: a poorly connected flex connector or an out-of-tolerance cell that shifts the internal component alignment. With correctly spec’d cells and proper installation, all sensors resume normal function. watchOS does not require sensor recalibration after a battery replacement.
Q4: How long does an Apple Watch S5 or SE battery last after replacement?
A: Apple’s published battery life for both the Series 5 and SE (1st Gen) is 18 hours under typical use — a mix of app usage, notifications, and workout tracking with heart rate on. A properly installed replacement cell restores runtime to that spec. Real-world figures depend heavily on Always-On Display usage (Series 5 only), GPS workout frequency, and notification volume. The battery itself is not the limiting variable with a new cell; usage pattern is.
Q5: What is the difference between the A2277 and A2181 — can they be substituted?
A: No. A2277 (245mAh) is physically sized for 40mm Watch cases; A2181 (296mAh) is physically sized for 44mm cases. They are different dimensions, different capacities, and different connectors. Installing the wrong size will result in fitment failure — the cell will either not fit or the connector will not reach the board. Always match the battery P/N to the Watch case size before installation.
Q6: What is the recommended installation temperature for the heat-softening step, and does your battery packaging account for Watch-specific repair tooling?
A: The standard recommendation for softening Apple Watch display adhesive is 70–80°C applied evenly for 60–90 seconds using a heat pad or heat gun with temperature control. Higher temperatures risk OLED damage; lower temperatures leave adhesive insufficiently softened and increase separation force, raising the risk of cracking the display. Our packaging includes the battery with protective wrapping suited for the Watch’s compact form factor. We can include Watch-specific tooling (suction handle, plastic opening picks, replacement adhesive strip) in OEM kit configurations from 200 pcs on request.
