Coolpad CP3321ST Replacement Battery 3.7V 1350mAh

Coolpad CP3321ST / Belleza — 3.7V Li-ion Replacement Battery (CPLD-442)

This is a 3.7V, 1350mAh Li-ion replacement battery for the Coolpad CP3321ST, CP3321AT, CP3321, and Belleza smartphones. It replaces OEM part CPLD-442 when the original cell no longer holds a charge or fails to power the handset. Capacity listed is from product data: 1350mAh (5Wh).

• CP3321 and Belleza platform compatibility: The CP3321ST, CP3321AT, CP3321, and Belleza share the same battery bay dimensions and connector pinout. All four models use the CPLD-442 cell format — same 57.30 × 43.00 × 5.20mm footprint, same voltage rail, same BMS communication protocol.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a CP3321ST unit. The BMS accepted the new cell without error flags, charge termination triggered correctly at capacity ceiling, and protection cutoff activated as expected at low-voltage threshold.
• Fuel gauge recalibration on first install: After swapping this cell in, disable fast charging and run one complete discharge-to-charge cycle before enabling high-current charging. The fuel gauge IC is calibrated to the old cell's discharge curve — one full cycle lets it map the new cell before fast charge pushes current into an uncalibrated profile.

Sudden shutdown at 20–30% on the Coolpad CP3321ST

This is a voltage cliff failure. At around 20–30% reported charge, the cell voltage drops sharply under the combined load of the modem radio and screen backlight. The fuel gauge IC still reports remaining capacity, but the actual cell voltage falls below the SoC threshold the BMS will sustain. The phone shuts off to protect the cell even though the percentage readout hasn't hit zero. One full recalibration cycle — full drain to auto-shutoff, then charge uninterrupted to 100% — resets the coulomb counter and reduces the gap between reported and real voltage.

Phone shows incorrect battery percentage after cell replacement

The fuel gauge IC stores a learned discharge curve from the old cell. When the new CPLD-442 is installed, that stored curve no longer matches actual cell behaviour, so the reported percentage drifts from real state of charge. You may see the percentage jump several points or stall during charging. Run one complete discharge cycle from 100% down to auto-shutoff, then charge back to 100% without interruption. After that single cycle, the coulomb counter recalibrates to the new cell and percentage accuracy stabilises.