About this replacement
Nolan B5 / B901L / B901R / N4 Series — 3.7V Li-ion Replacement Battery (PL053448P)
This is a 3.7V 800mAh Li-ion cell that replaces the original battery in the Nolan B5, B901L, B901R, and N4 wireless headsets. It fits the slim 50.00 × 34.20 × 5.20mm cavity directly. When the factory cell no longer holds a charge, this swap restores full headset function without replacing the unit.
- B5, B901L, B901R, and N4 compatibility: These models share the same cell format, connector pinout, and BMS handshake protocol. A single 3.7V cell with the correct dimensions and protection circuit covers the entire group.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the B5 platform. The onboard BMS accepted the pack without fault codes, and the protection circuit tripped correctly at low-voltage cutoff.
- Base station first-cycle logging: On first use, seat the headset in the base station and let it complete a full charge cycle before making a call. DECT headsets log the new cell during that first docked cycle — skipping it causes the talk-time indicator to read inaccurately for the first several uses.
Base station showing a charging error after fitting the new cell
The base station communicates with the headset's BMS before it begins charging. If the new cell arrives at storage voltage — typically around 3.6V — the base may flag a handshake mismatch or display a charge fault. This is not a faulty battery. Dock the headset, leave it seated for at least 15 minutes without interruption, and the base station will re-initialise the charge cycle. If the error clears, the BMS has accepted the pack and charging proceeds normally.
Headset cutting out mid-call even with a charged battery
The Nolan B5 runs both the audio codec and the DECT radio from the same 3.7V cell simultaneously. Under that combined draw, a cell weakened by age or a shallow charge can sag below the BMS cutoff threshold mid-transmission. The headset drops the call and may restart. Check that the cell reached a full charge before the call — the base station indicator light should show solid green, not pulsing. If cut-outs continue after a verified full charge, the cell voltage at load is dropping below 3.2V; confirm with a multimeter on the contacts.