About this replacement
Amazfit A1918 / A1808 / A1818 Series — 3.8V Li-Polymer Replacement Battery (PL502524G)
This 3.8V, 380mAh Li-Polymer cell replaces the original battery in the Amazfit A1918, A1808, A1818, A1807 Nexus, and six additional Amazfit smartwatch variants. The cell measures 24.00 × 24.20 × 5.10mm and matches OEM part numbers PL502524G, PL512524G, and PL502524V. It restores full operation across fitness tracking, heart rate monitoring, and notifications without replacing the watch.
- A1918 / A1808 / A1818 platform compatibility: These models share the same 3.8V cell format, connector pitch, and BMS handshake protocol. Swapping between them uses the same physical cell and the same fuel gauge IC — that is why one part number covers the entire line.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the A1918 platform. The BMS accepted the new cell without error flags, and the fuel gauge updated state-of-charge correctly after a full charge cycle from near-zero.
- Post-swap charger step for Amazfit fuel gauge IC: Place the watch on its magnetic charger immediately after fitting this cell and charge to 100% before first use. The fuel gauge IC on this platform loses its reference point when the cell is removed and cannot recalibrate without one complete charge cycle from near-zero.
Why the A1918 reports inaccurate battery percentage after a cell swap
The Amazfit A1918 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell over time. When you remove the old battery, the IC loses its accumulated reference data entirely. A new cell with a full charge will confuse it — the IC sees no history and defaults to a percentage it cannot verify. The fix is straightforward: fit the new cell, charge to 100%, then allow one normal discharge cycle. After that single cycle, the percentage readout stabilises.
Charge contacts not making on magnetic charger after reassembly
If the watch does not begin charging after a battery swap, the magnetic charger contacts have likely shifted during reassembly. The back cover alignment on the A1918 series is tight — even a fraction of a millimetre off-centre breaks the contact circuit. Remove the back cover, re-seat the battery connector, and refit the cover with even pressure around the full perimeter. Confirm charging has started by checking for the charging indicator within 30 seconds of placing it on the charger.