About this replacement
Chuango WS-108 — 7.4V Li-Polymer Replacement Battery (UPS-A890)
This 7.4V 600mAh Li-Polymer cell replaces the factory battery in the Chuango WS-108 wireless door and window sensor. The WS-108 is a contact sensor used in Chuango intruder alarm systems to detect entry point breaches. At 43.10 x 25.60 x 12.10mm, it fits the original battery cavity without modification.
- WS-108 contact sensor fit: The WS-108 runs its RF transmitter and reed switch circuit from a single 7.4V Li-Polymer cell. The form factor is specific — a wrong-voltage or oversized cell will either fail to communicate with the panel or won't seat in the housing.
- Bench tested on actual hardware: We ran this cell through the WS-108's BMS handshake and confirmed the panel registered a valid battery state within the expected window. The protection circuit responded correctly to both charge cutoff and low-voltage disconnect thresholds.
- Post-installation zone check timing: Do not run a zone diagnostic immediately after swapping this cell. The WS-108 needs 24–48 hours on float charge before the panel will report an accurate battery state. Triggering a test before that window closes can produce a false low-battery fault on the panel display.
Alarm panel showing low battery hours after installing a new WS-108 cell
This is a BMS reporting delay, not a faulty cell. The Chuango panel polls each zone sensor for battery state shortly after the system arms or a zone triggers, and a freshly installed Li-Polymer cell hasn't yet reached the float voltage threshold the panel expects. The panel interprets the slightly depressed resting voltage as low. Leave the system powered and armed for 24–48 hours — the fault will clear once the cell stabilises at full float, typically around 8.4V.
WS-108 sensor stops transmitting after a door opens
If the sensor trips but the panel receives no alert, the most common cause is a marginal cell voltage — the reed switch actuates but the RF transmitter doesn't have enough current to complete the burst. Check the cell voltage under load; anything below 6.8V means the protection circuit is near its cutoff floor. A cell that reads 7.2V at rest but sags below 6.8V on transmission needs replacing. Fit the new UPS-A890 cell, reseat the housing cover fully, and confirm the tamper circuit is closed before testing.