About this replacement
UMI UMIDIGI F2 — 3.85V Li-Polymer Replacement Battery (1ICP/6/65/87-2)
This 3.85V, 5000mAh Li-Polymer battery replaces the original cell in the UMIDIGI F2 smartphone. It matches the OEM part number 1ICP/6/65/87-2 and fits the F2's internal battery bay at 87.00 x 65.04 x 4.70mm. Use it when the original cell no longer holds adequate charge or fails to power the device through normal daily tasks.
- UMIDIGI F2 fitment: The F2 uses a single-cell Li-Polymer pack at 3.85V nominal with a proprietary ribbon connector and a BMS that handshakes with the phone's charge IC. This replacement carries the same connector pinout and BMS profile, so the charge IC recognises the cell without throwing a fault.
- Bench tested on actual hardware: We cycled this cell on the F2 board, monitoring charge IC communication and BMS cutoff response. The protection circuit tripped correctly at the low-voltage threshold and resumed charging without manual reset when voltage recovered above the lockout floor.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. The F2's fuel gauge IC is still calibrated to the old cell's discharge curve. One slow cycle lets the coulomb counter map the new cell's actual capacity before fast-charge current loads an uncalibrated state of charge reading.
Sudden shutdown at 20–30% on the UMIDIGI F2 after a cell swap
After replacing the battery, some F2 units shut down abruptly when the reported charge sits between 20% and 30%. This is a voltage cliff issue — the fuel gauge IC still references the old cell's discharge curve, so the percentage shown does not match the new cell's actual voltage under load. When the modem or display draws a burst of current, the real cell voltage drops below the hardware cutoff even though the OS still shows charge remaining. One full slow discharge cycle down to automatic shutdown, followed by a complete charge, forces the coulomb counter to re-anchor its curve to the new cell. After that cycle, the shutdowns stop.
USB-PD fast charge not activating on the first cycle after replacement
The UMIDIGI F2's charge IC negotiates fast-charge voltage with the BMS before ramping current. On a brand-new cell, the BMS ships in a conservative state and may not complete that handshake on the first plug-in, causing the phone to fall back to standard 5V charging. This is normal — it is not a fault with the cable or the charger. Complete one full charge at standard rate, unplug, and reconnect to the fast charger. The BMS handshake completes correctly on the second cycle, and the charge IC steps up to the negotiated fast-charge voltage.