Coolpad 8900 Compatible Battery 3.7V 1200mAh CPLD-39

Coolpad 8900 / N900S / 8910 — 3.7V Li-ion Replacement Battery (CPLD-39)

This is a 3.7V, 1200mAh Li-ion replacement battery for the Coolpad 8900, N900S, and 8910 smartphones. It replaces the original CPLD-39 cell when the existing battery no longer holds charge or causes unexpected shutdowns. Capacity is 4.44Wh — identical to the factory specification.

• 8900, N900S, and 8910 compatibility: These three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — all three accept the CPLD-39 cell without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the 8900 platform. The BMS accepted the new cell on first connection, charge termination triggered correctly at 4.2V, and the protection circuit tripped as expected on over-discharge.
• Fuel gauge recalibration after install: On first use, disable any fast-charge mode and run one complete discharge-charge cycle at standard rate. This gives the fuel gauge IC a clean discharge curve to calibrate against before high-current charging is applied to the new cell.

Sudden shutdown at 20–30% on the Coolpad 8900

This is a voltage cliff issue, not a capacity fault. The 8900's modem and display draw brief high-current spikes that a degraded — or freshly installed, uncalibrated — cell cannot sustain at that state of charge. Voltage drops below the BMS cutoff threshold instantly, and the phone shuts off even though the fuel gauge still shows charge remaining. After one full calibration cycle, the fuel gauge IC maps the new cell's actual discharge curve, and the phantom shutdowns stop.

Phone reports wrong battery percentage after cell swap

The fuel gauge IC on the 8900 stores a learned discharge model from the old cell. When a new CPLD-39 goes in, that stored model no longer matches the real cell chemistry, so reported percentage drifts — often jumping erratically or freezing at one value. The fix is one uninterrupted full discharge down to auto-shutoff, followed by a full charge to 100% at the standard charge rate. After that cycle, the coulomb counter resets its baseline against the new cell and percentage readings stabilise.