Asus ZenWatch 2 Replacement Battery 3.7V 270mAh

Asus ZenWatch 2 WI502QF — 3.7V Li-Polymer Replacement Battery (C11N1541)

This 3.7V, 270mAh lithium-polymer cell replaces the original battery in the Asus ZenWatch 2 (WI502QF). It fits the 25.65 x 25.80 x 3.96mm cavity and connects to the same BMS board that manages the display, heart rate sensor, and Bluetooth radio. OEM part numbers covered: 0B200-01760100 and C11N1541 1ICP4/26/25.

• WI502QF platform fit: The ZenWatch 2 WI502QF uses a square form-factor cell with a specific connector orientation tied to its fuel gauge IC. This cell matches that footprint and connector pin-out exactly — the BMS handshake completes without error codes on the watch OS.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the ZenWatch 2 platform. The BMS accepted the new cell, the fuel gauge initialised correctly after a full charge cycle, and charge termination triggered cleanly at 4.2V.
• Post-swap charge requirement: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before use. The fuel gauge IC on the ZenWatch 2 loses its reference point when the cell is removed — it cannot report accurate percentages until it runs one full charge cycle from near-zero.

Why the ZenWatch 2 charge contacts fail to connect after reassembly

The ZenWatch 2 uses a magnetic pogo-pin charger that seats against two contact points on the watch case back. When the rear cover is reseated after a battery swap, even a half-millimetre shift in the back plate can misalign those contacts. The watch will sit on the charger and show no charging indicator, which looks like a dead battery but is actually a mechanical alignment issue. Press the watch firmly onto the charger and rotate it slightly — if the LED or charging icon appears, realign and reseat the back cover before closing it fully.

Watch not pairing with phone after battery replacement

Removing the battery cuts power to the BLE radio mid-session, which causes the ZenWatch 2 to drop its stored pairing credentials on some firmware versions. The phone retains the old pairing record, but the watch no longer recognises it — so the connection attempt silently fails. Fix this by going into your phone's Bluetooth settings, forgetting the ZenWatch 2 entry, then re-initiating pairing from the Asus ZenWatch app. The watch should appear as a new device within 30 seconds of entering pairing mode.