Panasonic TX320 Replacement Battery 3.7V 700mAh Li-ion

Panasonic TX320 / EBTX320 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 700mAh (2.59Wh) Li-ion cell for the Panasonic TX320 and EBTX320 mobile phones. It replaces the original cell when the existing battery no longer holds enough charge to get through normal daily use. Voltage and connector match the original hardware directly.

• TX320 and EBTX320 fit: Both models share the same battery bay dimensions, 3.7V voltage rail, and connector pinout. The BMS handshake protocol is identical across the two, so one cell covers both variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge, standby, and active load conditions on the TX320 platform. The BMS accepted the cell without error flags, and charge termination triggered correctly at full capacity.
• 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 map the new cell's discharge curve accurately before high-current charging is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the TX320 after a cell swap

The TX320's fuel gauge IC stores a discharge curve calibrated to the old, degraded cell. When you install a fresh cell, that stored curve no longer matches reality. The phone's reported percentage and the cell's actual voltage fall out of sync. Under screen-on or modem load, the new cell's voltage can look like a cliff to the OS even when real capacity remains. Run one full discharge down to auto-shutdown and a full uninterrupted charge to let the coulomb counter recalibrate — shutdowns at false-low percentages typically stop after that cycle.

Phone not powering on after the replacement cell sat in storage

Li-ion cells self-discharge during storage. If the cell voltage dropped below roughly 2.5V, the BMS enters a lockout state and blocks normal charge current to prevent damage. The TX320 will show nothing on screen — no charging indicator, no vibration. Connect the phone to a low-current USB charger (a standard 5V/500mA port, not a fast charger) and leave it for 20–30 minutes without pressing the power button. Once the BMS detects voltage climbing above its recovery threshold, normal charging resumes and the phone will boot.