About this replacement
ZOPO ZP980 / ZP980+ Series — 3.7V Li-ion Replacement Battery (BT78S / BT78T)
This is a 3.7V, 1900mAh Li-ion cell that fits the ZOPO ZP980, ZP980+, C2, and C3 smartphones. It replaces OEM part numbers BT78S and BT78T. If your original cell swells, won't hold a charge, or drops out unexpectedly, this is the direct swap.
- ZP980 and ZP980+ platform fitment: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One cell covers both variants without adapter or modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on ZP980 hardware. The BMS accepted the cell without error flags, and the charge IC held current limits within spec throughout each cycle.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard rate. This gives the fuel gauge IC time to map the new cell's discharge curve before any high-current charging pushes current into an uncalibrated cell.
Sudden shutdown at 20–30% on the replacement cell
This happens because the fuel gauge IC is still running its algorithm against the old cell's discharge curve. The new cell hits a voltage cliff under modem or screen load — the IC reads it as 20% remaining but the cell is already below the cutoff threshold. The phone shuts down to protect the cell, even though the percentage display looked safe. One full discharge to zero followed by an uninterrupted charge to 100% resets the coulomb counter and resolves this.
Device won't power on after sitting in storage
Li-ion cells stored at low charge levels self-discharge over time. If the cell drops below roughly 2.5V, the BMS triggers a lockout to prevent a damaged charge cycle. The phone shows nothing — no boot screen, no charging animation. Connect to a wall charger, not a PC USB port, and leave it for 20–30 minutes before pressing power. The charge IC on a wall adapter can push enough trickle current to lift the cell above the BMS re-enable threshold, typically around 2.8V.