Hagenuk Fono 3 Replacement Battery BP-MPB16 3.7V 1200mAh

Hagenuk Fono 3 — 3.7V Li-ion Replacement Battery (BP-MPB16)

This is a 3.7V, 1200mAh Li-ion cell built to fit the Hagenuk Fono 3 smartphone. It replaces OEM part BP-MPB16 (also cross-referenced as DR6-2009 and DR11-2009). Use it when the original cell no longer holds charge or causes unexpected shutdowns.

• Fono 3 fitment: The Fono 3 uses a slim removable cell at 53.18 × 34.00 × 6.80mm. This replacement matches those physical dimensions and the 3.7V nominal voltage rail the device's charge IC expects. The connector orientation and BMS communication lines align with the stock configuration.
• Bench tested on actual hardware: We cycled this cell through charge and load on the bench. The BMS held cutoff correctly at the low-voltage threshold and accepted a full charge-IC handshake without triggering protection lockout at either end of the voltage range.
• Fuel gauge recalibration on first use: On first installation, disable fast charging if available and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the OS starts drawing on that data for percentage estimates.

Sudden shutdown at 20–30% on the Fono 3 after a cell swap

A fresh Li-ion cell has a steeper voltage cliff than a worn one. The Fono 3's fuel gauge IC was calibrated to the old cell's discharge curve, so it reports 25% remaining while the actual cell voltage is already dropping toward the low-voltage cutoff threshold. Under modem or screen load, current draw accelerates the voltage drop faster than the gauge tracks it. The BMS triggers a hard shutdown to protect the cell before the OS registers a low-battery warning. One full discharge-charge cycle at standard rate resets the coulomb counter and resolves this.

Fono 3 showing erratic battery percentage after replacement

Percentage jumping — say, from 60% to 45% in seconds, or stalling at a fixed number for an extended period — points to a fuel gauge IC that has not yet mapped the new cell. The IC holds state data from the previous cell in non-volatile memory. It applies that old curve to a cell with different internal resistance and capacity characteristics, producing inaccurate readouts. Drain the battery until the phone powers off on its own, then charge uninterrupted to 100% without removing the cable. That single full cycle forces the IC to rewrite its reference curve to the new cell.