Polycom KIRK 3.6V Cordless Phone Replacement Battery NT7B65KL

Polycom KIRK 3040 / 4020 / 4040 — 3.6V Ni-MH Replacement Battery (NT7B65KL)

This is a 3.6V, 700mAh Ni-MH battery for Polycom KIRK cordless DECT handsets. It fits the KIRK 3040, KIRK 4020, KIRK 4040, and several related models in the KIRK series. Voltage, capacity, and physical dimensions match the OEM specification — 45.00 × 31.10 × 10.50mm.

• KIRK series handset compatibility: These KIRK models share the same 3.6V cell format, connector pinout, and physical housing cavity. The same pack suits the full range because Polycom kept that battery specification consistent across the KIRK 3040, 4020, and 4040 platforms.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on KIRK hardware. The BMS accepted the charge without flagging an error, and the cell voltage held within the expected 3.6V nominal band across the cycle.
• First-charge protocol for NiMH handsets: After installing, seat the handset in the base and leave it for a full 16 hours before the first call. NiMH cells shipped in partial-charge storage need a slow initial charge to reach rated 700mAh capacity — skipping this shortens the effective charge cycle from the start.

Talk time shorter than original battery after replacement

NiMH cells arrive from storage at reduced capacity — this is normal, not a defect. The first three to five full charge-discharge cycles condition the cells and progressively unlock rated capacity. A KIRK handset that feels short on talk time after day one will typically improve noticeably by cycle three. Run full cycles: charge fully in base, use until the low-battery indicator activates, then return to base.

Base station showing no-charge or error light with a new pack installed

KIRK base stations check incoming voltage before committing to a charge cycle. A NiMH pack that has self-discharged below roughly 3.0V during storage can fall under the base acceptance threshold — the charger sees a suspect reading and holds off. Remove the handset, wait 30 seconds, and reseat it firmly so the contacts align. If the error persists, check that the cell voltage reads at least 3.0V with a multimeter before concluding there is a fault.