CATERPILLAR S30 Replacement Battery 3.8V 2900mAh Li-Polymer

CATERPILLAR S30 — 3.8V Li-Polymer Replacement Battery (APP-12F-B55951-CXX-111)

This 3.8V, 2900mAh Li-Polymer battery replaces the factory cell in the CATERPILLAR S30 rugged smartphone. It matches the original voltage rail, connector, and physical footprint at 93.76 × 55.70 × 3.70mm. Capacity is drawn from the product spec — 11.02Wh total energy.

• S30 platform fitment: The S30 uses a sealed unibody housing with a single battery cavity toleranced to this cell's exact dimensions. The BMS on this cell mirrors the original handshake protocol so the phone's charge IC accepts it without triggering a hardware fault code.
• Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on the S30 platform. The BMS negotiated correctly with the phone's charge controller, and the protection circuit tripped as expected at both overvoltage and undervoltage thresholds.
• First-cycle fuel gauge reset on the S30: After installation, disable fast charging and run one complete discharge down to auto-shutoff, then charge to 100% on standard charge. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated profile.

Sudden shutdown at 20–30% on the S30 after a cell swap

The S30's fuel gauge IC retains the discharge curve of the old, degraded cell. When a new cell is installed, the coulomb counter still references that old curve and miscalculates the voltage cliff. The phone cuts power when the new cell hits a voltage point the IC interprets as empty — even though usable charge remains. One full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% forces the IC to recalibrate. After that cycle, shutdowns at false low-percentage readings stop.

Device won't power on after extended storage with a deep-discharged cell

If the S30 sat unused with a flat battery, the cell voltage may have dropped below 2.5V — the BMS lockout threshold. At that point the BMS disconnects the cell entirely and the phone shows no response to the power button or charger. Connect the phone to a wall adapter (not a PC USB port) and leave it untouched for 20–30 minutes. The charger delivers a trickle pre-charge that brings the cell back above the 2.5V re-enable threshold, after which the BMS reconnects and normal charging resumes. If the LED stays dark past 45 minutes on the wall adapter, the cell is unrecoverable and replacement is required.