Amazfit A1805 Smartwatch Replacement Battery 3.8V 190mAh

Amazfit A1805 — 3.8V Li-Polymer Replacement Battery (PL472020V)

This is a 3.8V, 190mAh Li-Polymer cell for the Amazfit A1805 smartwatch. It replaces the original PL472020V battery when the watch can no longer hold a charge through a normal day. Dimensions are 20.40 × 19.90 × 4.70mm — measure your existing cell before fitting if you are unsure.

• A1805 platform fit: The A1805 uses a compact Li-Polymer pouch cell on a 3.8V nominal rail. The connector pinout and cell footprint match the OEM PL472020V spec, so the replacement seats in the same bay without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the A1805 platform. The onboard BMS accepted the new cell without fault flags, and the charge circuit stepped down correctly from CC to CV phase at the expected cutoff.
• Fuel gauge re-initialisation after swap: Place the watch on its charger immediately after fitting this cell. Charge it to 100% before first use. The fuel gauge IC on the A1805 loses its reference when the original cell is disconnected — it cannot recalibrate until it sees a full charge cycle from near-zero on the new cell.

Why the A1805 reports wrong battery percentages after a cell swap

The A1805 uses a coulomb-counting fuel gauge IC that tracks charge state relative to a stored baseline. When you remove the old cell, that baseline is lost. The IC wakes up on the new cell with no reference point and guesses — badly. This causes the watch to show 85% on a nearly empty cell, or drop from 60% to 0% in minutes. A full charge-to-100% cycle from near-zero resets the counter and restores accurate reporting.

Watch not pairing to phone after battery replacement

Removing the battery ends the active BLE session between the A1805 and the paired phone. The phone retains the old device record, but the watch boots as if it has never paired. Go into your phone's Bluetooth settings, forget the Amazfit device entirely, then re-pair through the Zepp app from scratch. Do not attempt to reconnect directly from the Bluetooth menu — the app handles the authentication handshake that the system Bluetooth menu skips.