About this replacement
TCL S700T / J620 — 3.7V Li-ion Replacement Battery (TLi020E7)
This is a 3.7V, 2000mAh Li-ion replacement battery for the TCL S700T and J620 smartphones. It slots into the original battery bay and connects to the same flex contact used by the factory cell. Voltage and physical footprint match OEM specifications at 71.21 × 60.20 × 4.45 mm.
- S700T and J620 compatibility: Both handsets share the same battery bay dimensions, connector pitch, and 3.7V nominal voltage rail. OEM part numbers TLi020E7, TLi020D2, TLi020B2, TLi020E1, and TLi020JD all cross to this cell — TCL used multiple part codes across production runs of the same platform.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the S700T platform. The BMS accepted the new cell without triggering an overcurrent fault, and the charge IC ramped to full current within the first cycle.
- Fuel gauge recalibration on first use: After installing this battery, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the coulomb counter a clean reference curve against the new cell before the OS starts reading percentage from it.
Why the S700T reports wrong battery percentage after a cell swap
The fuel gauge IC on the S700T learns the battery's discharge curve over time and stores it in memory. When you swap cells, that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The OS reads the old curve and displays a percentage that can be off by 10–25%. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and re-anchors the curve to the replacement cell.
Sudden shutdown at 20–30% charge remaining on the replacement cell
This happens when the cell voltage drops below the modem or screen load threshold before the displayed percentage reaches zero — a voltage cliff where the cell cannot sustain current under peak draw. It is more common in the first few cycles before the fuel gauge IC has calibrated to the new cell. Run two complete discharge-charge cycles without interruption. If shutdowns persist after calibration, check that the battery connector tab is fully seated — a partial contact increases internal resistance and accelerates the voltage drop under load.