About this replacement
Panasonic KX-TU327 Series — 3.7V Li-ion Replacement Battery (BJ-LT100010)
This is a 3.7V, 700mAh Li-ion cell built to OEM part number BJ-LT100010. It fits the KX-TU327, KX-TU327EX, KX-TU327EXBE, KX-TU328, and five additional variants in the same series. Swap it in when the original cell no longer holds a charge or causes unexpected shutdowns.
- KX-TU327 and KX-TU328 series compatibility: These models share the same 3.7V voltage rail, connector pinout, and BMS handshake protocol — which is why a single cell covers the full lineup. Swapping between variants does not require a different battery.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the KX-TU327 platform. The BMS accepted the new cell without error flags, and the charge IC reached termination voltage cleanly at 4.2V.
- Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if available and run one full discharge-to-charge cycle. The fuel gauge IC is calibrated to the old cell's discharge curve — one complete cycle resets it against the new cell so percentage readings stay accurate.
Why the KX-TU327 reports wrong battery percentage after a cell swap
The KX-TU327 uses a fuel gauge IC that tracks battery state based on a coulomb counter and a learned discharge curve from the old cell. A new cell has a different internal resistance and a fresh discharge curve the IC has never seen. Until the IC recalibrates, it maps current draw against the wrong reference, producing percentage readings that are off by 10–20%. One full discharge below 10% followed by a complete charge to 100% gives the IC enough data to rebuild its curve against the new cell.
Sudden shutdown at 20–30% remaining on the KX-TU327
This happens when the cell voltage drops sharply under load — a voltage cliff caused by high current draw from the modem or display that the cell cannot sustain at that state of charge. The phone's protection circuit cuts power before the OS can log a normal shutdown. It is not a faulty battery — it is an uncalibrated fuel gauge triggering cutoff at the wrong point. Run one full discharge-charge cycle and check whether the shutdown threshold moves; if the phone still cuts out, confirm resting voltage sits above 3.6V after a full charge.