NEC N919 Replacement Battery 3.7V 700mAh Li-ion

NEC N919 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 700mAh Li-ion cell for the NEC N919 smartphone. It replaces the original battery when capacity fade causes shortened use between charges or the phone begins shutting down unexpectedly. Voltage and capacity match the OEM spec exactly.

• NEC N919 fitment: The N919 uses a compact 700mAh cell with a 3.7V nominal rail. This replacement matches that voltage threshold so the phone's power management IC accepts the cell without triggering a voltage mismatch fault on boot.
• Bench tested on actual hardware: We ran a full charge-discharge cycle and monitored BMS handshake on power-up. The protection circuit tripped correctly at the low-voltage cutoff, and the phone's charge IC accepted the cell without error codes on the first connection.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the OS begins reporting percentages from it. Skip this and the percentage readout will drift for several cycles.

Why the N919 reports wrong battery percentage after a cell swap

The N919 uses a fuel gauge IC that builds its capacity model against the cell it has been cycling with. When you install a new cell, the IC still holds the old discharge curve in memory. It reads state-of-charge against that stale model, so the percentage shown on screen doesn't match actual remaining capacity. One full discharge to auto-off followed by a complete charge resets the coulomb counter and re-anchors the gauge to the new cell. After that cycle, percentage accuracy returns to normal.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — typically during screen-on use, a call, or data sync — faster than the fuel gauge IC can track. The phone reads 25% on screen but the cell voltage has already sagged below the BMS cutoff threshold under that current draw, triggering an immediate shutdown. It is not a faulty battery — it is the fuel gauge IC still running against an uncalibrated curve. Run one full discharge-charge cycle without fast charging, and the shutdowns will stop once the counter resets and tracks the actual voltage curve under load.