Crosscall Core X4 LPN385375 Compatible Battery 3.85V 3500mAh

Crosscall Core X4 — 3.85V Li-Polymer Replacement Battery (LPN385375)

This is a 3.85V, 3500mAh Li-Polymer battery for the Crosscall Core X4 rugged smartphone. It replaces OEM part numbers LPN385375 and COX4BAT100. Fit this battery when the original cell no longer holds charge or the phone shuts down unexpectedly under load.

• Core X4 cell compatibility: The Core X4 uses a 3.85V nominal Li-Polymer cell with a BMS that monitors charge state via an on-board fuel gauge IC. The replacement cell matches the original voltage rail and physical dimensions (69.80 × 55.90 × 5.65mm) so the connector seats correctly and the BMS handshake completes without error flags.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Core X4 platform. The BMS accepted the cell without rejecting the charge cycle, and the protection circuit responded correctly to both over-charge and low-voltage cutoff thresholds.
• First-cycle fuel gauge recalibration: After fitting this cell, disable fast charging and run one full discharge-to-charge cycle at standard rate. The fuel gauge IC on the Core X4 calibrates its coulomb counter against the new cell's discharge curve during this first cycle — skipping it can leave the percentage display inaccurate for days.

Sudden shutdown at 20–30% on the Core X4 after a cell swap

The Core X4's fuel gauge IC stores a discharge model from the previous cell. When a new cell with a different internal resistance profile is fitted, the IC underestimates how quickly voltage will drop under modem and screen load. The phone reads 25% but the actual cell voltage collapses below the cutoff threshold the moment the LTE radio fires a high-power burst. Running one full unconstrained discharge cycle forces the coulomb counter to relearn the new cell's voltage cliff, typically around 3.5V under load. After that cycle, the shutdowns stop.

Phone won't power on after the replacement battery sat in storage

Li-Polymer cells self-discharge in storage, and if the cell drops below approximately 2.5V per cell, the BMS enters a protective lockout state and blocks normal boot. The Core X4 will show no response when the power button is pressed. Connect the phone to a wall charger — not a PC port — and leave it for 20–30 minutes without pressing anything. The charge IC trickle-charges the cell to a safe threshold, the BMS releases its lockout, and the phone boots normally. If the cell reads above 3.0V and the phone still won't respond, reseat the battery connector before assuming cell failure.