About this replacement
Apple Watch Series 7 41mm — 3.85V Li-Polymer Replacement Battery (A2663)
This is a 3.85V, 280mAh Li-Polymer cell built to replace the original A2663 battery in Apple Watch Series 7 41mm models — covering A2473, A2475, and A2476. It restores power to the display, processor, heart rate sensor, and GPS radio. Dimensions are 26.10 x 20.10 x 4.60mm, matching the original cell footprint.
- Series 7 41mm platform fit: The A2473, A2475, and A2476 share the same internal chassis and battery bay. All three accept the A2663 cell on the same connector and flex layout — no adapter or modification needed.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Series 7 41mm unit. The BMS handshake completed without fault codes, and the fuel gauge IC accepted the new cell reference after a full charge cycle.
- Post-swap charger protocol: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The fuel gauge IC on Series 7 loses its capacity reference when the cell is removed — it cannot recalibrate without a full charge from near-zero after the swap.
Why the Series 7 fuel gauge reads wrong after a cell swap
The Apple Watch Series 7 uses a dedicated fuel gauge IC that tracks capacity by monitoring charge and discharge curves over time. When you remove the original cell, the IC loses its stored reference data entirely. The new cell starts with no learned curve, so the gauge has no baseline to calculate remaining charge. Until you complete one full charge cycle from near-zero to 100%, the percentage readout will be unreliable — expect wildly jumping numbers or a stuck reading for the first cycle.
Watch not pairing to iPhone after battery replacement
Removing the battery cuts power completely, which terminates the active Bluetooth Low Energy session between the watch and iPhone. The watch does not automatically re-establish that session on reboot — the phone sees it as an unknown device. Open the Watch app on your iPhone, go to General > Reset > Erase Apple Watch Content and Settings, then re-pair from scratch. You do not lose health data stored in the Health app — that syncs to iCloud before the reset.