Telematrix BATT-IPN Cordless Phone Compatible Battery 3.7V 650mAh

Telematrix IPN964591 Series — 3.7V Li-Polymer Replacement Battery (BATT-IPN)

This 3.7V, 650mAh lithium-polymer battery replaces the original pack in the Telematrix IPN964591, IPN965591, IPN984591, and IPN985591 cordless handsets. It restores talk time and standby capacity to a handset that has stopped holding a charge. Same voltage, same footprint at 42.15 × 31.00 × 6.34mm — it seats correctly in the battery compartment without modification.

• IPN900-series handset compatibility: These four models share the same battery bay dimensions and 3.7V single-cell architecture. The connector and BMS handshake are identical across the range, so one part number covers all of them.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on a DECT handset platform. The BMS held the correct cutoff voltage under both standby and active RF transmit load without triggering a premature shutdown.
• First-charge protocol for Li-Polymer cordless handsets: After installing, seat the handset in the base and leave it for a full uninterrupted charge before making any calls. Li-Polymer cells in low-drain standby devices that ship at partial state of charge need one complete cycle to calibrate the handset's fuel gauge correctly.

Talk time shorter than original battery after replacement

A new Li-Polymer cell ships at a storage charge — typically 40–60% of rated capacity. The handset's internal fuel gauge reads this partial state as a full charge until a complete cycle resets it. Run one full charge followed by normal use until the handset signals low battery, then charge it fully again. After that cycle, the fuel gauge recalibrates and talk time reflects the rated 650mAh capacity.

Handset not pairing with base station after battery swap

Removing the battery cuts all power to the DECT module, and some IPN-series handsets clear their pairing data when power is fully lost. The fix is a manual re-registration: place the handset on the base, press and hold the registration button on the base unit until the handset display prompts for a PIN, then enter the default PIN (typically 0000). Once confirmed, the handset reconnects to the base and operates normally.