Panasonic KX-TU150 Replacement Battery 454854AR 3.7V 1300mAh

Panasonic KX-TU150 / KX-TU155 Series — 3.7V Li-ion Replacement Battery (454854AR)

This is a 3.7V, 1300mAh Li-ion cell that replaces the original 454854AR battery in the Panasonic KX-TU150, KX-TU150EXR, KX-TU155, and KX-TU155EXCN. The original battery in these phones degrades over two to three years of use, causing sudden shutdowns or an inability to hold a charge. Swapping to a fresh cell restores the phone to its original operating state.

• KX-TU150 and KX-TU155 platform fit: Both the TU150 and TU155 share the same battery bay dimensions, connector pinout, and BMS handshake protocol — the 454854AR cell fits both without modification or adapters.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on the KX-TU150 platform. The BMS accepted the charge immediately, voltage held steady across the discharge curve, and the protection circuit tripped correctly at the low-voltage threshold.
• Fuel gauge recalibration on first use: After fitting this cell, disable any fast-charge mode and run one complete discharge-to-charge cycle. The phone's fuel gauge IC is calibrated to the old cell's discharge curve — one full cycle resets the coulomb counter against the new cell before high-current charging begins.

Why the KX-TU150 reports wrong battery percentage after a cell swap

The KX-TU150 uses a fuel gauge IC that builds its capacity model from repeated charge-discharge data on the installed cell. When you swap to a new cell, that learned model no longer matches the new cell's actual voltage-to-capacity curve. The gauge reads voltage correctly but maps it against outdated capacity data, so 75% displayed might mean 55% actual. One complete discharge below 10% followed by a full charge to 100% forces the IC to reset its coulomb counter and rebuild the curve against the new cell.

Sudden shutdown at 20–30% on the KX-TU150 after an old battery ages

An aged Li-ion cell loses its ability to sustain voltage under load even when the resting voltage reads healthy. On the KX-TU150, the backlight and RF transmitter draw current spikes that pull a degraded cell below the BMS cutoff voltage — the phone shuts off instantly rather than displaying a low-battery warning. The fuel gauge shows 20–30% because it measured resting voltage, not loaded voltage. A replacement cell with full capacity sustains above 3.4V under these load spikes and eliminates the cutoff.