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Apple Watch Series 2 A1848 Compatible Battery 3.82V 270mAh

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From $26.99 USD $33.99
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Fits Apple Watch Series 2 model MQJU2LL/A and replaces OEM part A1848.
3.82V and 270mAh rating sustains all-day timekeeping, fitness tracking, and sensor operation on this smartwatch platform.
Connector uses Apple's magnetic charging pogo pins; ensure flush seating into the watch case during reassembly.
We bench-tested this cell in an MQJU2LL/A unit; the fuel gauge IC calibrated correctly across a full charge cycle with no early cutoff.
After fitting, place the watch on its charger immediately and charge to 100% — the smartwatch fuel gauge cannot calibrate without a full cycle from near-zero after a cell swap.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

Disclaimer

⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

3.82V

Amp

270mAh

Apple MQJU2LL/A Series — 3.82V Li-Polymer Replacement Battery (A1848)

The A1848 is a 3.82V, 270mAh Li-Polymer cell for Apple Watch Series 2. It fits MQJU2LL/A, MQKW2LL/A, MQKV2LL/A, MR2W2LL/A, and 13 additional Series 2 model numbers sharing the same internal layout. This replacement restores power to the display, processor, heart rate sensor, and wireless radio.

  • Series 2 model compatibility: All listed Series 2 models use the same A1848 cell, voltage rail, and connector pinout. The BMS handshake and charge IC are identical across the lineup, so one cell covers the full group.
  • Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on Series 2 hardware. The BMS responded correctly to the watch's charge IC — no false low-battery flags and no cutoff errors under normal sensor load.
  • Post-swap charge requirement: After fitting the new cell, place the watch on its magnetic charger immediately and charge to 100% before wearing it. The Series 2 fuel gauge IC loses its reference point when the original cell is removed. Without a full charge cycle from near-zero, it cannot recalibrate and will report inaccurate percentages throughout the day.

Why Apple Watch Series 2 Battery Percentage Reads Wrong After a Cell Swap

The Series 2 uses a fuel gauge IC that tracks charge state by measuring coulombs in and out relative to a stored reference. When you remove the old cell, that reference is wiped. The new cell arrives partially charged, so the IC has no baseline to work from. It will display whatever percentage it can approximate — often stuck at 0%, 1%, or an inflated number. A full charge to 4.35V resets the reference and lets the IC anchor its calculations correctly.

Watch Not Connecting to iPhone After Battery Replacement

Removing the battery kills the active BLE session between the watch and the paired iPhone. The watch does not automatically re-establish pairing after a hard power loss — it presents as an unknown device on the phone side. Go to the Watch app on iPhone, tap your watch, select "Unpair Apple Watch," then set it up again as a new device. You do not lose health data stored in iPhone Health, only data not yet synced at the time of removal.

Compatible Models

MQJU2LL/A MQKW2LL/A MQKV2LL/A MR2W2LL/A MQKU2LL/A MQJQ2LL/A GSRF-MQJQ2LL/A MRQE2LL/A MQKX2LL/A MQJP2LL/A MQKY2LL/A MR352LL/A MQL62LL/A MQJN2LL/A Watch Series 3 LTE 38mm Watch Series 3 4G 38mm A1858

Replaces Part Numbers

A1848

Technical Specifications

Voltage3.82V
Amp Hours270mAh
Capacity270mAh
Rate1.03Wh
Net Weight4.4g /0.16 oz
Gross Weight54.4g /1.92 oz
Approximate Weight54.4g /1.92 oz
Dimension 24.62 x 16.56 x 5.52mm

Product Highlights

  • Brand: Apple
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-Polymer
  • Battery Type: Li-Polymer
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Apple Watch Series 2 shows 0% and won't turn on right after fitting the new A1848 battery — did I get a dead cell?

The cell is almost certainly fine. The Series 2 fuel gauge IC loses its charge reference when the original battery is removed, and the new cell arrives partially charged with no baseline for the IC to read. Place the watch on its magnetic charger immediately and leave it until it reaches 100%. Once it completes a full charge cycle, the IC recalibrates and the watch will power on and display an accurate percentage.

The new battery is draining completely within a single day — is something wrong with the replacement cell?

This is almost always a settings issue rather than a cell fault. Always-on heart rate monitoring running alongside active notifications and Wi-Fi scanning can draw this 270mAh cell down quickly. Check that Background App Refresh is limited and that heart rate is not set to continuous in Privacy settings. If drain persists past the first three full charge cycles, verify that the magnetic charge contacts are seating flush — a partial connection delivers slow trickle charges that never fully top the cell off, making it appear to drain faster than it does.

The heart rate sensor seems to be pulling more power from the new battery than it did from the old one — is that normal?

Yes, and it is expected for the first week. The old degraded cell had high internal impedance, which actually suppressed sensor polling frequency as the watch throttled background tasks to protect a weak cell. The new A1848 has lower impedance, so the watch runs heart rate sampling and wireless sync at full rate again. Power draw appears higher by comparison, but total daily use reflects the watch operating as intended. Consumption levels out after four to five full charge cycles once the fuel gauge IC has a stable reference.

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