Caterpillar BM1S1B Replacement Battery 3.87V 4800mAh CCW5000-1

CATERPILLAR BM1S1B / CAT S75 — 3.87V Li-Polymer Replacement Battery (CCW5000-1)

This is a 3.87V, 4800mAh Li-Polymer replacement battery for the CATERPILLAR BM1S1B and CAT S75 rugged smartphones. It uses OEM part number CCW5000-1 and slots into the same bay as the original cell. Capacity is rated at 18.58Wh.

• BM1S1B and CAT S75 fitment: Both models run the same 3.87V Li-Polymer cell on a shared voltage rail with the same connector pinout and BMS handshake protocol. One cell covers both devices without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the CAT S75 platform. The BMS accepted the cell without fault flags, and the charge IC reached full termination voltage at 4.35V as expected.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Sudden shutdown at 20–30% on the CAT S75 after a cell swap

The CAT S75 runs a demanding modem stack and a high-brightness display simultaneously. Under that combined load, a new cell with an uncalibrated fuel gauge IC can report 25% remaining while the actual cell voltage has already sagged below the BMS cutoff threshold. The phone shuts down not because the battery is dead, but because the voltage dips below approximately 3.4V under load before the gauge catches up. One full discharge-charge cycle without fast charging resets the coulomb counter and eliminates this cliff.

Phone not powering on after the replacement battery sat in storage

Li-Polymer cells self-discharge in storage, and if the voltage drops below 2.5V per cell, the BMS enters lockout mode to prevent damage. The phone will show no response — no charge indicator, no boot screen. Connect the device to a 5V wall charger, not a USB hub, and leave it for 15–20 minutes before attempting to power on. The charge IC delivers a low-current precharge to bring the cell back above 2.9V, at which point the BMS releases and normal charging resumes.