Panasonic TX220 Compatible Battery 3.7V 1500mAh Li-ion

Panasonic TX220 — 3.7V Li-ion Replacement Battery

This is a 3.7V Li-ion replacement battery rated at 1500mAh (5.55Wh) for the Panasonic TX220 smartphone. It fits the original battery slot and connects to the same charge IC and fuel gauge circuit. Use this when your original cell no longer holds a charge or the phone shuts down unexpectedly.

• TX220 cell fitment: The TX220 uses a single Li-ion cell on a 3.7V rail. The connector, physical dimensions, and BMS handshake point all match the original battery spec — the phone's charge IC sees the replacement as a standard Li-ion cell and begins CC/CV charging without any manual prompting.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the TX220 platform. The BMS accepted the cell on first connection, charge termination triggered correctly at full voltage, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging starts pushing current into an uncalibrated state register.

Sudden shutdown at 20–30% on the TX220 after a cell swap

The TX220's fuel gauge IC calibrates its state-of-charge model against the original cell's discharge curve. When a new cell goes in, that curve no longer matches — the phone hits a voltage cliff under modem or screen load before the gauge reaches zero. The result is an abrupt shutdown even though the percentage display still shows charge remaining. One full discharge-charge cycle without fast charging lets the coulomb counter reset and remap the new cell's actual capacity curve.

Phone reports wrong battery percentage after replacement

The fuel gauge IC on the TX220 stores a learned discharge profile from the old cell in its state registers. A new cell has a different internal impedance and discharge slope, so the stored profile is immediately out of step. The percentage reading will jump erratically or plateau at values that don't reflect actual charge. Drain the battery until the phone powers off, then charge uninterrupted to 100% — this forces a full coulomb counter reset against the new cell.