About this replacement
Cisco 8821 — 3.8V Li-Polymer Replacement Battery (CP-BATT-8821)
This 3.8V, 1700mAh Li-Polymer battery replaces the original pack in the Cisco 8821 wireless IP phone handset. It restores full handset operation when the original cell has degraded or failed. The OEM part numbers CP-BATT-8821, GP-S10-374192-010H, and 74-102376-01 all cross-reference this unit.
- Cisco 8821 handset fit: The 8821 uses a slim Li-Polymer cell to keep the handset lightweight for mobile clinical and warehouse environments. This pack matches the original connector orientation, BMS communication pins, and physical footprint — the handset firmware recognises the cell without prompting an alert.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the 8821 platform. The BMS reported correct cell voltage at rest and held the charge threshold without triggering a low-battery alert prematurely.
- First-charge protocol for the 8821: After installing, seat the handset in its charging cradle and leave it undisturbed for a full charge cycle before making any calls. Li-Polymer cells shipped at partial state of charge need one full charge to calibrate the handset's fuel gauge correctly.
Talk time shorter than rated after swapping the 8821 battery
A new Li-Polymer pack ships at a storage charge — typically 40–60% — not a full 3.8V. If you start using the handset before running a complete charge cycle, the fuel gauge in the 8821 calibrates against that lower starting point. The handset then reads the battery as depleted earlier than it actually is. Run two or three full charge-discharge cycles and the reported capacity will stabilise at the rated 1700mAh.
Handset not pairing with the base station after battery replacement
Removing the battery from the 8821 cuts power completely, which can wipe the active DECT pairing stored in volatile memory. The handset comes back up without its base registration. To restore it, go to Settings → Phone Information → Add a Phone on the Cisco Unified Communications Manager, then follow the on-screen re-registration steps on the handset. Once registered, the pairing survives future battery swaps as long as the base retains its configuration.