About this replacement
ZTE U288 / S207 — 3.7V Li-ion Replacement Battery (Li3710T42P3h623846)
This is a 3.7V, 1200mAh Li-ion cell built to the OEM spec for the ZTE U288 and S207 smartphones. It fits the original battery slot with matching connector and dimensions (62.64 × 38.02 × 4.82 mm). Voltage and capacity match the Li3710T42P3h623846 part number exactly.
- U288 and S207 compatibility: Both models run on the same 3.7V single-cell platform and use the same connector pinout and BMS handshake protocol. One cell covers both devices without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the U288 platform. The BMS accepted the cell without triggering a fault, and the charge IC completed a full CC/CV cycle to 4.2V.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.
Why the U288 reports wrong battery percentage after a cell swap
The fuel gauge IC on the U288 uses a coulomb counter that was trained on the original cell's discharge curve. When a new cell goes in, the stored curve no longer matches actual cell voltage under load. The phone reads a stale lookup table and reports whatever percentage the old curve predicted at that voltage. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the counter and lets the IC build a fresh curve for the new cell.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff issue, not a capacity problem. Under modem activity or screen-on load, current draw spikes and the cell voltage drops sharply — faster than the fuel gauge predicted. The phone's hardware protection circuit sees the voltage dip and cuts power before the reported percentage reaches zero. After completing the first full calibration cycle described above, the fuel gauge IC learns the new cell's actual voltage sag profile and the early shutdowns stop. If they persist after two full cycles, check that the connector is fully seated — a loose pin raises contact resistance and worsens the sag.