SpectraLink BBK87120 Cordless Phone Replacement Battery 3.7V 2200mAh

SpectraLink 8742 / PBL87420 — 3.7V Li-ion Replacement Battery (BBK87120)

This is a 3.7V, 2200mAh Li-ion replacement battery for the SpectraLink 8742 cordless handset. It fits the 8742, PBL87420, PBL87440, and Pivot 8741 series handsets that run on the BBK87120 pack. Swap it in when the original no longer holds a charge through a standard shift.

• 8742 / PBL87420 / Pivot 8741 platform fit: These handsets share the same 3.7V single-cell architecture, BBK87120 connector pinout, and BMS handshake protocol — one battery pack covers the entire platform.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a SpectraLink 8742 handset. The BMS accepted charge from a standard base station without error flags, and cell voltage held steady across the discharge curve under normal DECT transmit load.
• First-charge protocol for Li-ion handsets: After installing, seat the handset in the base and charge uninterrupted until the charge indicator clears. SpectraLink bases use a trickle-top phase — interrupting it early leaves the cell at 90–95% and skews the handset's fuel gauge from day one.

Talk time shorter than expected after battery swap

A new Li-ion cell ships at partial state of charge — typically 40–60%. The handset's onboard fuel gauge calibrates against the first few full charge-discharge cycles, so early talk time will read low. Run three full cycles: charge to completion, use until the low-battery warning triggers, then recharge fully. By cycle three, the gauge aligns with the cell's actual 2200mAh capacity and reported talk time stabilises.

Handset loses DECT pairing after battery replacement

Removing the battery cuts power completely to the handset's registration memory on some SpectraLink 8700-series units. When power is restored with the new pack, the handset boots without a stored base station pairing. Go to the handset menu under System or Registration, select your base station, and re-enter the system PIN — the default is typically 0000. If the base still rejects the handset, power-cycle the base station before attempting re-registration.