Coolpad Defiant CPLD-417 Replacement Battery 3.85V 2200mAh

Coolpad Defiant / BTR3635A — 3.85V Li-ion Replacement Battery (CPLD-417)

This is a 3.85V, 2200mAh Li-ion replacement battery for the Coolpad Defiant smartphone. It uses OEM part number CPLD-417 and also fits the BTR3635A variant. Swap it in when the original cell no longer holds a charge or causes unexpected shutdowns.

• Defiant and BTR3635A fit: Both models run the same 3.85V power rail and share an identical connector pinout and BMS handshake protocol, which is why a single cell covers both.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the Defiant platform. The BMS accepted the cell without error flags, and the charge IC cycled cleanly through trickle, constant-current, and constant-voltage stages.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging for the first complete discharge-charge cycle. The fuel gauge IC needs one full cycle against the new cell's discharge curve before it can report accurate percentages — running fast charge into an uncalibrated cell skews the coulomb counter.

Sudden shutdown at 20–30% on a freshly installed cell

This is a voltage cliff problem, not a capacity problem. Under peak modem or display load, the new cell's voltage drops faster than the fuel gauge IC expects based on the old cell's curve. The Defiant's power management IC interprets the voltage sag as a critically low cell and triggers a hard shutdown before the reported percentage reaches zero. One full discharge-to-shutdown and recharge cycle forces the fuel gauge to relearn the new cell's voltage-versus-capacity curve. After that recalibration cycle, the shutdowns stop and percentage readings stabilise.

OS battery percentage jumping or stuck after replacement

The Defiant's fuel gauge IC stores the discharge curve of the original cell in memory. When a new cell goes in, the stored curve no longer matches the actual cell behaviour, so percentage readings jump, stall, or freeze — typically between 40% and 80%. The fix is a full uninterrupted discharge down to auto-shutdown, then a full charge to 100% with the screen off. That single cycle resets the coulomb counter and aligns the IC to the new cell. After one complete cycle, readings should track smoothly within 3–5% accuracy.