UMIDIGI BISON Replacement Battery 1ICP/6/63/81 3.87V 4800mAh

UMI UMIDIGI BISON 2021 — 3.87V Li-Polymer Replacement Battery (1ICP/6/63/81)

This 3.87V 4800mAh lithium-polymer cell replaces the original battery in the UMIDIGI BISON (2021). It fits directly into the BISON's battery bay using the OEM part number 1ICP/6/63/81. Dimensions are 77.90 × 63.30 × 5.30mm — match these against your original cell before installing.

• UMIDIGI BISON 2021 fitment: The BISON uses a 3.87V nominal Li-Polymer cell tied to a charge IC that expects a specific charge termination voltage of 4.35V. This replacement matches that voltage ceiling, so the on-board charge IC does not reject the cell or flag a fault during the constant-voltage phase.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on BISON hardware. The BMS accepted full CC-CV charging without triggering an overcurrent cutoff, and cell voltage held within spec under sustained screen-on and modem load.
• First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. The fuel gauge IC on the BISON calibrates its coulomb counter against the cell's discharge curve — skipping this step leaves the IC reading from the old cell's data, causing erratic percentage jumps.

Sudden shutdown at 20–30% on the UMIDIGI BISON after a cell swap

A degraded original cell develops high internal impedance, and the fuel gauge IC builds its discharge model around that aged curve. When a fresh low-impedance cell goes in, voltage drops faster under modem and display load than the IC predicts. The IC sees a voltage cliff — cell voltage sags below the cutoff threshold while the reported percentage still reads 20–30%. One full slow-charge cycle forces the coulomb counter to relearn the new cell's actual capacity and discharge rate, eliminating the false cutoff.

USB-PD fast charging not activating on the first cycle after replacement

The BISON's charge controller handshakes with the battery BMS before enabling high-current fast charging. On a brand-new cell, the BMS has no charge history logged, and some charge controllers default to trickle or standard charge on the first cycle as a precaution. This is not a fault with the replacement cell. Charge fully once at the standard rate, then reconnect the charger — the fast-charge handshake completes normally once the BMS has one completed cycle recorded.