UMIDIGI S2 Replacement Battery 3.85V 5000mAh 1ICP/5/64/58-2

UMI UMIDIGI S2 — 3.85V Li-Polymer Replacement Battery (1ICP/5/64/58-2)

This 3.85V, 5000mAh Li-Polymer cell replaces the original battery in the UMIDIGI S2 smartphone. It matches the OEM part number 1ICP/5/64/58-2 and fits the S2's battery bay at 87.05 × 64.60 × 4.85mm. Capacity is rated at 19.25Wh — identical to the factory spec.

• UMIDIGI S2 fitment: The S2 uses a sealed rear-panel design with a direct flex-ribbon connector. This cell matches that connector pinout and the BMS handshake voltage thresholds the S2's charge IC expects — no adaptation required.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S2 platform. The BMS held charge termination at the correct 4.35V cutoff and the protection circuit tripped cleanly at the low-voltage floor without hanging the charge IC.
• Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one full discharge-to-charge cycle at standard rate. This lets the S2's fuel gauge IC map its coulomb counter to the new cell's discharge curve before high-current charging begins.

Sudden shutdown at 20–30% on the UMIDIGI S2 after a cell swap

The S2's fuel gauge IC retains the discharge curve of the old, degraded cell in its coulomb counter. When a new cell is installed, the IC's voltage model no longer matches what the cell actually delivers under load. The modem radio and display draw current spikes that push the new cell's terminal voltage below the IC's shutdown threshold — even though state-of-charge is genuinely high. One full uninterrupted discharge cycle from 100% to automatic shutdown, followed by a full charge, forces the coulomb counter to recalibrate against the new cell's actual voltage floor.

USB fast charge not activating on the first cycle after replacement

The S2's charge controller negotiates fast-charge current based on the BMS reporting a valid cell impedance range. On a brand-new cell, impedance reads slightly higher than an in-service cell — some charge ICs interpret this as a fault condition and fall back to standard 5V/1A charging. This typically clears after the first full charge cycle, once the BMS registers the cell as settled. If fast charge still does not activate after one complete cycle, check that the cable and adapter support the correct voltage step — the S2 expects 9V/2A negotiation.