BlackBerry Z3 TLp025A2 Replacement Battery 3.8V 2500mAh

BlackBerry Z3 / STJ100-1 — 3.8V Li-Polymer Replacement Battery (TLp025A2)

This 3.8V, 2500mAh Li-Polymer battery is a direct cell replacement for the BlackBerry Z3 (STJ100-1). It replaces OEM part numbers TLp025A2 and FIH435573. Install it when the original cell no longer holds a usable charge or causes unexpected shutdowns.

• Z3 and STJ100-1 platform fit: Both model designations share the same physical cell footprint (73.07 × 54.34 × 4.35mm), connector pinout, and BMS communication protocol — this replacement cell slots into either variant without modification.
• Bench tested on actual hardware: We ran this cell on a Z3 unit and confirmed the BMS handshake initialised correctly, charge termination triggered at 4.35V, and the protection circuit tripped as expected on a simulated over-discharge to 2.5V per cell.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge down to automatic shutdown, then charge to 100% uninterrupted. This gives the Z3's fuel gauge IC one complete cycle to map the new cell's discharge curve before fast-charge current is applied to an uncalibrated cell.

Why the Z3 reports wrong battery percentage after a cell swap

The Z3 uses a coulomb-counter fuel gauge IC that builds its capacity model from the original cell's discharge curve. Swap the cell and the IC is still reading against that old curve. The result is percentage jumps, premature low-battery warnings, or a meter that reads 40% when the phone shuts down. One full uninterrupted discharge-to-shutdown and charge-to-100% cycle resets the IC's reference points against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff failure — not a capacity problem. Under high-current load from the modem or display, the cell voltage drops sharply below the BMS cutoff threshold even though the fuel gauge still shows charge remaining. It happens most often on cells that haven't completed a full calibration cycle. Run one complete discharge-to-shutdown cycle, then check open-circuit cell voltage; it should read at least 3.7V at the 30% mark after calibration.