SoftBank 003Z Replacement Battery Li3713T42P3h444865 3.7V 1300mAh

SoftBank 003Z — 3.7V Li-ion Replacement Battery (Li3713T42P3h444865)

This is a 3.7V, 1300mAh Li-ion cell for the SoftBank 003Z smartphone. It replaces OEM part numbers Li3713T42P3h444865 and Li3712T42P3h444865. Install it when the original cell no longer holds a usable charge across a full day of calls and messaging.

• 003Z platform fit: The 003Z uses a 3.7V single-cell architecture with a connector and BMS handshake matched to this cell form factor. Both OEM part numbers reference the same voltage rail and physical footprint — either crosses directly to this replacement.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a 003Z board. The BMS accepted the cell on first connection, charge current ramped normally, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. The fuel gauge IC on the 003Z calibrates its coulomb counter against the new cell's discharge curve — skipping this step causes the percentage readout to drift by as much as 15% in normal use.

Sudden shutdown at 20–30% on the 003Z after a cell swap

This happens because the fuel gauge IC still references the discharge curve of the old, degraded cell. When the 003Z's modem fires a high-current burst — during a call or data handoff — the new cell's actual voltage under load drops below the threshold the IC is tracking. The processor reads this as a critical low-voltage event and shuts down immediately. One full discharge-to-charge cycle rewrites the IC's internal curve map to match the new cell, and the shutdowns stop.

Phone warm near the battery during the first few charges

A new Li-ion cell has higher internal impedance than a broken-in cell. During the first two or three charge cycles, the 003Z's charge IC pushes current into a cell that hasn't yet settled to its nominal impedance, and the extra resistance converts some of that energy to heat. This is normal and tapers off after the cell has completed a few full cycles. If warmth persists beyond the third full charge, check that nothing is blocking airflow around the back of the handset during charging.