Panasonic KX-TU446 Replacement Battery 3.7V 900mAh 514047AR

Panasonic KX-TU446 / KX-TU456 Series — 3.7V Li-ion Replacement Battery (514047AR)

This is a 3.7V, 900mAh Li-ion cell built to the OEM spec of part number 514047AR. It fits the Panasonic KX-TU446, KX-TU456, KX-TU446/4, KX-TU466EXBE, and related variants in this flip-phone family. If your phone drops off charge fast or won't hold power through a normal day of calls, this cell replaces the original like-for-like.

• KX-TU446 and KX-TU456 series fit: These models share the same 3.7V single-cell architecture, connector pinout, and physical envelope — 50.70 × 40.00 × 5.50mm. The BMS handshake across this family uses the same charge termination signal, so one cell covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell through charge and load on a KX-TU446 unit. The BMS accepted the cell cleanly, charge termination triggered at the correct cutoff voltage, and the protection circuit responded to over-discharge conditions without fault codes.
• Fuel gauge recalibration after swap: On first use after installation, run the phone down to automatic shutdown, then charge it uninterrupted to 100%. This gives the fuel gauge IC one complete reference cycle against the new cell's discharge curve before it starts reporting accurate percentages.

Why the KX-TU446 reports wrong battery percentage after a cell swap

The phone's fuel gauge IC builds its capacity model by learning the discharge curve of whichever cell is installed. When the original worn cell is replaced, the IC still references the old curve — so it can show 40% remaining and cut off moments later. This isn't a fault with the replacement cell. One full discharge-to-shutdown followed by a complete uninterrupted charge resets the coulomb counter and aligns the gauge to the new cell's actual 900mAh curve. After that cycle, percentage readings stabilise.

Phone shuts down suddenly at 20–30% after installing the replacement

This is a voltage cliff issue, not a capacity problem. Under the load of an active call, the cell voltage can sag below the BMS cutoff threshold even when the gauge still reads 20–30% — because the fuel gauge hasn't recalibrated yet and is misreading state of charge. The fix is the same full discharge-recharge cycle described above. If shutdown at low percentage persists past two full cycles, check that the battery connector is fully seated — a loose contact increases internal resistance and worsens voltage sag under load, dropping the cell below 3.0V prematurely.