About this replacement
LG Watch Urbane 2nd Edition LTE — 3.85V Li-Polymer Replacement Battery (BL-S7)
This is a 3.85V, 400mAh lithium-polymer cell replacing the BL-S7 in the LG Watch Urbane 2nd Edition LTE. It fits W200, W280, and W280A variants. The cell powers the AMOLED display, Snapdragon 400 processor, heart rate sensor, and LTE radio simultaneously.
- W200, W280, W280A compatibility: These three model numbers share the same battery bay dimensions, 3.85V nominal rail, and connector pinout. One cell covers all three without modification.
- Bench tested on actual hardware: We fitted this cell to a W200 unit and confirmed the BMS accepted the new cell without error flags. Charge acceptance started immediately at 4.35V upper cutoff, and the fuel gauge IC registered charge state correctly after one full cycle.
- Fuel gauge calibration after cell swap: After fitting the new cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The fuel gauge IC on this platform cannot set a reliable reference point without a full charge cycle from near-zero following a cell swap.
Why the LTE radio shortens battery life more than Wi-Fi ever did
The W200 maintains a persistent LTE connection for standalone calls and notifications without a paired phone. That radio draws significantly more current than a BLE connection to a smartphone. On a 400mAh cell, continuous LTE standby is the single largest power consumer — more than the display or HR sensor. Disabling standalone LTE when a phone is nearby is the most effective way to extend discharge cycles on this cell.
Watch shows 0% and won't wake after battery swap
This is a fuel gauge IC reset, not a faulty cell. When the original battery is disconnected, the IC loses its reference charge state entirely and defaults to zero on restart. The watch may refuse to boot because firmware interprets 0% as a critically low state and blocks startup to protect the cell. Place it on the charger immediately after reassembly — once voltage climbs past approximately 3.7V, the IC re-references and the watch will boot normally.