Sharp HE312 Z3 Replacement Battery 3.85V 2950mAh

Sharp Z3 / L900S / FS8009 — 3.85V Li-Polymer Replacement Battery (HE312)

This is a 3.85V, 2950mAh lithium-polymer replacement cell for the Sharp Z3, L900S, and FS8009 smartphones. It uses OEM part number HE312 and slots directly into the original battery bay. Capacity is rated at 11.36Wh.

• Z3, L900S, and FS8009 compatibility: All three models share the same battery bay dimensions and voltage rail, and the BMS handshake requirements across these boards match the HE312 cell spec. The connector pinout and physical footprint — 112.40 × 45.00 × 3.52mm — are identical across the group.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Z3 board. The BMS accepted the cell without fault flags, fast charge negotiation completed normally after the first full cycle, and the fuel gauge IC tracked state of charge without erratic jumps once calibrated.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the Sharp Z3 after a cell swap

This is a voltage cliff issue, not a capacity defect. Under peak modem or screen load, cell voltage drops sharply at a certain state of charge — faster than the fuel gauge IC predicts using the old cell's curve. The phone's PMIC interprets this as a hard undervoltage condition and shuts down even though the percentage reading looks safe. One full discharge-charge cycle at standard rate recalibrates the coulomb counter to the new cell and pushes the reported cutoff threshold back into alignment with actual voltage behaviour.

Phone reports wrong battery percentage after fitting the HE312

The fuel gauge IC on the Z3 stores a discharge curve learned from the original cell. When a new cell goes in, that stored curve no longer matches real voltage-to-capacity behaviour, so the percentage reading drifts — often reading 100% too quickly or dropping suddenly in the last quarter. This is not a fault in the replacement cell. Charge the phone to 100%, let it discharge fully to auto-shutdown, then charge back to 100% without interruption. After that single cycle the IC rebuilds its curve against the new cell and percentage reporting stabilises.