CAT S50c A09QA008H Replacement Battery 3.75V 2600mAh

CAT S50c — 3.75V Li-Polymer Replacement Battery (A09QA008H)

This 3.75V, 2600mAh lithium-polymer cell replaces the original battery in the CAT S50c rugged smartphone. It matches the OEM part number A09QA008H and fits the S50c's internal bay with the same 60.40 × 55.50 × 5.90mm footprint. When the original cell degrades and the phone can no longer hold charge through a full shift, this cell restores capacity to factory spec.

• CAT S50c platform fit: The S50c runs a single-cell Li-Po architecture at 3.75V nominal. This cell matches that voltage rail and uses the same connector orientation and BMS communication lines as the factory unit — no adapter or modification needed.
• Bench tested on actual hardware: We cycled this cell on the S50c board and confirmed the BMS handshake completed without fault codes. The charge IC accepted the cell on the first cycle, and protection thresholds triggered correctly at both ends of the discharge curve.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter locks in its reference points — skipping this step often causes erratic percentage readings in the first week.

Sudden shutdown at 20–30% on the CAT S50c after a cell swap

The S50c's fuel gauge IC stores a discharge model calibrated to the original cell's internal resistance profile. A new cell has a different impedance curve, so the gauge misjudges remaining capacity. Under high-load events — active LTE, GPS, or screen-on — voltage drops faster than the gauge predicts, and the phone shuts down before the display percentage reaches zero. The fix is one full uninterrupted discharge to auto-off, followed by a complete charge to 100% at standard current. After that cycle, the coulomb counter recalibrates and shutdowns below 20% stop.

Phone warm near the battery compartment on the first charge

A new Li-Po cell starts with higher internal impedance than a broken-in cell. On first charge, the charge IC pushes current into a cell that resists it more than usual, converting more energy to heat at the cell surface. This is normal during the first one or two cycles and typically resolves as internal resistance drops. If the phone stays noticeably warm beyond the third full charge cycle, check that the charge IC is not defaulting to fast-charge mode — drop it to standard 5V/1A input for the next cycle and monitor temperature at the back panel above the battery bay.