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Apple Watch Series 4 44mm A2059 Replacement Battery 3.82V 290mAh

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From $26.99 USD $33.99
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Fits Apple Watch Series 4 44mm model A1976, replacing original battery part number A2059.
This 3.82V, 290mAh lithium-polymer cell restores full capacity to aging watches that show reduced runtime and sensor lag.
Connector sits flat against the watch logic board; polarity marked on cell contacts aligns with the board pads.
We charged this cell in a Series 4 dock and confirmed the fuel gauge IC accepted the new BMS handshake without fault codes.
After fitting the new cell, place the watch on its charger immediately and charge to 100% before first use — the fuel gauge IC on smartwatch platforms cannot calibrate without a full charge 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.

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

Voltage

3.82V

Amp

290mAh

Apple Watch Series 4 44mm — 3.82V Li-Polymer Replacement Battery (A2059)

This is a 3.82V, 290mAh Li-Polymer cell for the Apple Watch Series 4 44mm (A1976). It replaces the original A2059 battery when the watch can no longer hold charge or shuts down unexpectedly. The cell powers the display, processor, heart rate sensor, and all wireless functions.

  • Series 4 44mm platform fit: The A2059 footprint is specific to the 44mm Series 4 chassis. The 40mm variant uses a different cell with a different connector orientation. Fitting this cell to any other series risks connector damage and BMS mismatch.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Series 4 unit. The BMS accepted the cell without error flags, and the fuel gauge IC re-calibrated correctly after a full charge from near-zero.
  • Post-swap charge requirement: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The fuel gauge IC on the Series 4 loses its voltage reference during cell removal and cannot read state-of-charge accurately until it completes one full charge cycle from near-zero.

Why the Series 4 reports 0% immediately after a battery swap

The Series 4 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell. When you remove the old battery, the IC loses its reference point entirely. It has no way to know where the new cell sits in its charge curve until it sees a full cycle. The watch may display 0%, refuse to boot, or shut down within seconds of powering on. Charge the watch to 100% on the magnetic charger before using it — that single full charge resets the IC's baseline and the percentage readout will stabilise.

Watch not pairing with iPhone after battery replacement

Removing the battery kills the BLE session between the watch and the paired iPhone. The phone sees the watch as disconnected and may not automatically re-establish the link once the watch powers back on. The fix is not a software update — it is a manual re-pair. On the iPhone, open the Watch app, tap your watch, select Unpair Apple Watch, then set it up again as a new device. The watch retains its data if a backup completed before the swap.

Compatible Models

Watch Series 4 44mm A1976

Replaces Part Numbers

A2059

Technical Specifications

Voltage3.82V
Amp Hours290mAh
Capacity290mAh
Rate1.11Wh
Net Weight4.8g /0.17 oz
Gross Weight29.8g /1.05 oz
Approximate Weight29.8g /1.05 oz
Dimension 26.88 x 20.86 x 4.10mm

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 4 shows 0% and won't turn on after I replaced the battery — did I get a dead cell?

Almost certainly not a dead cell. The Series 4 fuel gauge IC loses its charge reference the moment you disconnect the old battery, so the watch has no idea what charge level the new cell is at. Place the watch on its magnetic charger and leave it until it reaches 100% without interruption. Once that full cycle completes, the IC re-calibrates and the watch will power on and display an accurate percentage.

The new battery is draining completely within a day — my old battery lasted longer even when it was worn out.

A fresh cell on a Series 4 can actually draw more current in the first few days because the fuel gauge IC is still calibrating and the watch may re-index sensors after the power interruption. Check whether always-on display is active and whether continuous heart rate monitoring is enabled — those two features together account for the majority of daily draw on this cell. Disable raise-to-wake temporarily and check Background App Refresh in the Watch app on your iPhone. If drain normalises after three to four full charge cycles, the IC has finished calibrating.

The magnetic charger isn't making contact properly since I reassembled the watch — the charging indicator doesn't appear.

The magnetic charger aligns to a specific contact point on the watch case back, and reassembly can shift the internal components by a fraction of a millimetre. Remove the watch from the charger, inspect the case back contacts for any adhesive residue or debris from the swap, and clean them with a dry cloth. Re-seat the back cover firmly and ensure it is flush before placing it on the charger again. If the indicator still does not appear, check that the battery connector is fully seated — a partially connected cell can prevent the charging circuit from engaging.

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