Polycom Spectralink 8400 Li-ion Compatible Battery 3.7V 1200mAh

Polycom Spectralink 8400 Series — 3.7V Li-ion Replacement Battery (1520-37214-001)

This 3.7V, 1200mAh Li-ion battery replaces OEM part 1520-37214-001 in the Polycom Spectralink 8400 series handsets. It fits the Spectralink 8400, 8450, 8452, and RS657 — all cordless DECT handsets used in enterprise and healthcare environments. Voltage and connector match the original, so no modification is needed during install.

• Spectralink 8400, 8450, 8452, and RS657 compatibility: These four models share the same battery bay dimensions, 3.7V rail, and connector pinout. The BMS in each handset uses the same charge acceptance protocol, so a single replacement battery works across the entire platform without modification.
• Bench tested on actual hardware: We ran this battery through full charge and discharge cycles on the Spectralink 8452. The BMS accepted the cell without error, held voltage within spec across the discharge curve, and the handset showed no low-battery warnings until the cell was genuinely depleted.
• First charge on the Spectralink base: After installing a fresh Li-ion cell, seat the handset in the Spectralink charging cradle and leave it there for a full charge cycle before the first call. The Spectralink base uses a trickle-to-constant-current profile — interrupting it early can cause the handset to report a lower capacity than the cell actually holds.

Talk time shorter than expected after fitting a new battery

Li-ion cells ship in a partial state of charge — typically 40–60% — to preserve cell chemistry during storage. If you pull the handset off the base before it reaches a full charge, the Spectralink firmware reads a lower usable capacity and adjusts its battery indicator accordingly. A full uninterrupted charge from the Spectralink cradle brings the cell to 4.2V and resets that reading. After one complete charge-to-depletion cycle, reported capacity aligns with the cell's actual 1200mAh rating.

Handset not pairing with the DECT base after battery replacement

Removing the battery cuts all power to the Spectralink handset, which clears the volatile memory holding the DECT pairing data on some firmware versions. The base station does not lose the pairing record — the handset does. To re-pair, hold the handset's power button for 10 seconds to trigger a full reset, then initiate the pairing sequence from the base administration interface. The handset should locate the base within 30 seconds if it is within 10 metres and the base is in pairing mode.