About this replacement
Alcatel 3X / 5X Series — 3.85V Li-Polymer Replacement Battery (TLp043D7)
This is a 3.85V, 4300mAh (16.56Wh) lithium-polymer cell replacing part number TLp043D7. It fits the Alcatel 3X, 5X, OT-5061A, and OT-5061K. Swap it in when the original cell no longer holds a charge or causes unexpected shutdowns.
- 3X and 5X series compatibility: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. All listed variants use the same 3.85V voltage rail, so one cell covers the full group without hardware modification.
- Bench tested on actual hardware: We cycled this cell through charge and load sequences on the OT-5061A. The BMS negotiated charge correctly, thermal output stayed within spec, and the protection circuit tripped as expected at the low-voltage cutoff threshold.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — it stops the OS reporting wrong percentages early.
Sudden shutdown at 20–30% on a replacement cell
This happens because the fuel gauge IC is still running a discharge model calibrated to the old, degraded cell. The new cell's actual voltage drops faster under modem and display load than the IC expects at that state-of-charge. When terminal voltage dips below the shutdown threshold — typically around 3.4V under load — the phone cuts out even though the gauge still shows charge remaining. One full uninterrupted discharge-to-charge cycle without fast charging resets the coulomb counter and resolves this. After that cycle, shutdowns at partial charge should stop.
Phone won't power on after the replacement cell sat in storage
Lithium-polymer cells self-discharge in storage. If the replacement shipped or sat unused below roughly 2.5V per cell, the BMS enters a lockout state to prevent damage and the phone will not respond to the power button. Connect a known-good charger and leave it for 15–20 minutes without pressing anything — the charge IC needs to trickle current into the cell until voltage rises above the BMS re-enable threshold. If the charging indicator appears, continue a full charge before attempting to boot. If no indicator appears after 30 minutes, check the cable and charge brick before assuming the cell is faulty.