About this replacement
Apple Watch Series 2 38mm — 3.8V Li-Polymer Replacement Battery (A1760)
This 3.8V, 270mAh lithium-polymer cell is a direct replacement for the A1760 battery inside the Apple Watch Series 2 38mm (MNNN2LL/A, MP032LL/A). It fits the compact 26.26 × 16.65 × 5.47mm cavity in the 38mm case. Swap it when your Series 2 can no longer hold a charge through a normal day.
- Series 2 38mm fitment: The MNNN2LL/A and MP032LL/A share the same 38mm case geometry and A1760 connector footprint. The battery management system on these watches uses the same BMS handshake — one cell spec covers both model numbers without modification.
- Bench tested on actual hardware: We ran this cell on a Series 2 unit and confirmed the BMS accepted the new cell without error flags. Charge acceptance was normal from the first cycle, and the fuel gauge IC updated its reference correctly after a full charge.
- Post-swap charge requirement: Place the watch on its magnetic charger immediately after fitting this cell and charge to 100% before first use. The fuel gauge IC on Series 2 cannot set an accurate reference point without a complete charge cycle from near-zero after a cell swap — skipping this step causes the percentage display to misread for days.
Why the Series 2 fuel gauge reads wrong after a battery swap
The Series 2 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out over time. When you remove the old cell, that reference is lost. The IC wakes up with no valid baseline and maps the new cell's open-circuit voltage to an estimated state of charge — which is often wrong. A full charge to 100% resets the coulomb counter and gives the IC a known endpoint to work from. Until that cycle completes, the percentage display will jump or read inaccurately.
Watch not pairing to iPhone after battery replacement
Removing the battery cuts power to the Bluetooth controller mid-session. The BLE stack on the watch loses its active pairing state, and watchOS can flag the device as unrecognised on next boot. This is not a fault with the new cell. Open the Watch app on your iPhone, go to General → Reset → Unpair Apple Watch, then re-pair from scratch. The watch will re-download its configuration and restore the Bluetooth session cleanly.