Kyocera Hydro Air SCP-64LBPS Replacement Battery 3.8V 2100mAh

Kyocera Hydro Air / Hydro Wave — 3.8V Li-ion Replacement Battery (SCP-64LBPS)

This is a 3.8V Li-ion cell rated at 2100mAh (7.98Wh), built to the same form factor as the original SCP-64LBPS. It fits the Kyocera Hydro Air, Hydro Wave, C6745, and C6745 LTE. Physical dimensions are 64.90 × 50.40 × 5.50mm — same as the OEM cell.

• Hydro Air and Hydro Wave compatibility: Both handsets run the same battery bay geometry, connector pinout, and BMS handshake protocol. Swapping between these models uses the same cell — the voltage rail and NTC thermistor wiring are identical across the C6745 platform.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the C6745 platform. The BMS accepted the cell without a handshake fault, thermal cutoff triggered correctly at elevated temperature, and the charge IC ramped to full current within the first cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard rate. The fuel gauge IC on the Hydro Air is calibrated to the old cell's discharge curve — one slow cycle lets it map the new cell before resuming high-current charging.

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

The Hydro Air's fuel gauge IC holds a discharge curve from the old cell. When a new cell goes in, the stored curve no longer matches actual cell voltage under load. The modem radio and display together draw enough current to cause a voltage cliff — the cell voltage drops sharply under that load even when the coulomb counter still reads 20–30%. One full discharge-charge cycle at standard rate forces the fuel gauge IC to relearn the new cell's voltage-versus-capacity curve and eliminates these premature shutoffs.

Phone stays at a fixed percentage for long stretches then drops fast

This is the fuel gauge IC recalibrating in real time against a cell it has not yet profiled. The coulomb counter is estimating state-of-charge from current flow, but without an accurate open-circuit voltage reference for the new cell, it plateaus then corrects sharply when voltage actually changes. It is not a fault in the replacement cell. Discharge the phone fully until it shuts off, then charge uninterrupted to 100% — after that cycle, percentage reporting stabilises.