About this replacement
Alcatel Plex / T780H — 3.85V Li-Polymer Replacement Battery (TLP037A7)
This 3750mAh (14.44Wh) Li-Polymer cell replaces the original TLP037A7 battery in the Alcatel Plex and T780H smartphones. It matches the stock voltage rail at 3.85V and fits the existing battery bay without modification. Install it when the original cell no longer holds a usable charge or causes unexpected shutdowns.
- Plex and T780H compatibility: Both models use the same 3.85V battery bay, connector pinout, and BMS handshake protocol — one cell covers both variants without any hardware change.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Alcatel platform and confirmed the BMS accepted the cell without fault codes. The charge IC brought the cell to 4.35V within spec and held the cutoff correctly at low state of charge.
- 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 build an accurate discharge curve against the new cell before high-current charging pushes load into an uncalibrated coulomb counter.
Why the Plex reports wrong battery percentage after a cell swap
The Alcatel Plex uses a coulomb counter that learns the discharge curve of whichever cell is installed. When you swap in a new cell, that stored curve no longer matches the fresh chemistry. The OS reads a stale model and displays percentages that don't reflect actual charge state. One full discharge to auto-shutdown followed by a complete uninterrupted charge resets the counter against the new cell's actual curve. After that cycle, percentage readings stabilise.
Sudden shutdown at 20–30% on the replacement cell
This happens when the modem or display draws a spike the cell can't sustain at low state of charge — voltage drops below the BMS cutoff threshold before the OS reads 0%. A fresh Li-Polymer cell at 3.85V nominal has a steeper voltage cliff in the bottom third of its charge than a partially degraded original cell. After one full calibration cycle, the fuel gauge IC maps the cliff correctly and the OS shuts down at the right point. If shutdowns persist past two full cycles, check the charge IC output — it should reach 4.35V at full charge before the issue can be attributed to the cell.