ZOPO BT78H ZP980 Compatible Battery 3.8V 2500mAh

ZOPO ZP980 / 2A / 9515 / C2 Series — 3.8V Li-Polymer Replacement Battery (BT78H)

This is a 3.8V, 2500mAh (9.5Wh) lithium-polymer cell that replaces the original BT78H battery in the ZOPO ZP980, 2A, 9515, and C2 smartphones. It fits models that share the same physical footprint (76.00 × 61.15 × 4.10mm) and connector layout as the factory cell. Swap it when the original cell no longer holds a usable charge through a normal day.

• ZP980 / 2A / 9515 / C2 platform compatibility: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — all accept the BT78H cell without modification or adapter.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the ZP980 platform, confirmed BMS communication at both ends of the voltage curve, and verified the protection circuit trips correctly on overcurrent.
• Fuel gauge recalibration on first use: On first installation, disable any fast-charge mode and run one complete discharge-to-charge cycle. This gives the fuel gauge IC a clean reference against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Why the ZP980 reports wrong battery percentage after a cell swap

The ZP980 uses a coulomb counter and fuel gauge IC that builds its charge model around the original cell's discharge curve. When a new cell goes in, that stored curve no longer matches the actual chemistry. The OS reads back estimated charge states that were calibrated to a degraded or different cell — so the percentage display runs inaccurate until the IC relearns the curve. One full discharge from 100% to automatic shutdown, followed by a full charge, resets the reference. After that cycle the reported percentage tracks the actual cell state correctly.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or display triggers a load spike the cell cannot sustain at its current voltage level. Li-polymer cells have a steeper voltage cliff in the lower charge range — if the fuel gauge IC is still calibrated to an older, higher-impedance cell, it underestimates the actual voltage drop under load. The phone's protection circuit sees the voltage dip below threshold and shuts down, even though the reported percentage still looks safe. Run a full discharge cycle so the IC maps the new cell's actual voltage curve, and check that the terminal resting voltage reads above 3.7V before the next session.