Kyocera KX13 Replacement Battery TXBAT10099 3.7V 750mAh

Kyocera KX13 / KX16 / KX160 — 3.7V Li-ion Replacement Battery (TXBAT10099)

This is a 3.7V, 750mAh Li-ion replacement battery for the Kyocera KX13, KX16, KX160, and KX12 flip phones. It uses OEM part number TXBAT10099 and measures 54.00 × 36.20 × 6.20mm — a direct physical match for the original cell slot. Capacity is rated at 2.78Wh.

• KX-series flip phone compatibility: The KX13, KX16, KX160, and KX12 share the same battery bay dimensions, 3.7V single-cell architecture, and connector pinout — all four models accept the TXBAT10099 cell without modification.
• Bench tested on actual hardware: We cycled this cell on a KX160 unit and confirmed the BMS accepted charge handshake correctly, held stable voltage through a full discharge curve, and did not trigger low-voltage cutoff prematurely.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge to automatic shutoff, then charge uninterrupted to 100% before normal use. The KX-series fuel gauge IC calibrates its coulomb counter against the first full discharge curve — skipping this causes the percentage readout to drift immediately.

Why the KX13 reports wrong battery percentage after a cell swap

The KX-series fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The gauge reads voltage against the old map and outputs a percentage that drifts — often showing 80% when the phone is close to shutoff. One full discharge-to-shutoff cycle followed by an uninterrupted charge forces the IC to rebuild its reference curve against the new cell and restores accurate readings.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem's minimum operating threshold under transmit load — even though the gauge still shows charge remaining. The KX13's GSM radio pulls current in bursts during a call; if internal cell resistance is slightly elevated on a new cell, voltage sags briefly below 3.2V and the phone cuts out. The fix is to complete two full discharge-charge cycles first, which conditions the cell and lets the BMS confirm the actual low-voltage floor before the phone relies on it under peak current draw.