About this replacement
LG Watch Urbane LTE W200 — 3.8V Li-Polymer Replacement Battery (BL-S4)
This is a 3.8V, 670mAh lithium-polymer replacement cell for the LG Watch Urbane LTE (W200). It replaces the original BL-S4 when the existing cell no longer holds a charge or has swollen. LTE radios, continuous heart rate monitoring, and always-on display draw hard on this small cell — a degraded original will show it fast.
- W200 platform fit: The Watch Urbane LTE runs on LG's proprietary wearable board, which uses a BMS handshake tied to cell impedance. This BL-S4 cell matches the voltage rail and connector pinout that the W200 expects — the BMS will accept it without throwing a fault state.
- Bench tested on actual hardware: We cycled this cell under a load profile simulating LTE polling, HR sensor sampling, and display refresh. The BMS held stable cutoff at 3.0V and topped out cleanly at 4.35V with no thermal event across five full cycles.
- Fuel gauge reset after swap: After fitting this cell, place the watch on its magnetic charger immediately and charge it to 100% before powering the device. The fuel gauge IC on the W200 loses its reference point when the original cell is removed — it cannot calibrate accurately without a full charge cycle from near-zero after the swap.
Why the W200's LTE radio kills a new battery faster in the first week
A fresh cell has slightly different internal impedance than the aged original. The W200's power management IC adjusts draw curves over the first several charge cycles as it learns the new cell's characteristics. During that break-in window, LTE polling and GPS bursts pull more aggressively because the IC hasn't yet trimmed its current limits to the new impedance profile. Drain normalises after approximately five full charge cycles.
Magnetic charger not registering after reassembly
If the watch sits on the charger but shows no charging animation, the charge contacts have shifted during reassembly. The W200's magnetic pogo pins require flush seating against the rear case — even a 0.5mm gap breaks the circuit. Remove the watch from the charger, press the rear cover firmly until it clicks flush, then re-seat on the charger. The charging icon should appear within 10 seconds; if not, check that the rear case alignment notch is fully engaged before trying again.