Binatone B200 TJB-1 Replacement Battery 3.7V 1000mAh

Binatone B200 / BB200 Speakeasy Series — 3.7V Li-ion Replacement Battery (TJB-1)

This is a 3.7V, 1000mAh Li-ion cell (3.7Wh) for the Binatone B200, BB200, Speakeasy Mobile Plus, and Speakeasy series handsets. It replaces OEM part numbers TJB-1 and BB100. When the original cell degrades and can no longer hold voltage under call or screen load, this cell restores normal function.

• B200 and Speakeasy series fitment: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — 54.61 × 35.16 × 5.31mm. The same TJB-1 cell runs across all listed variants because the voltage rail and charge IC spec did not change across that production run.
• Bench tested on actual hardware: We ran this cell through charge-discharge cycles on a B200 unit and confirmed the BMS accepted charge current without triggering a protection cutoff. Voltage under simulated call load held above 3.5V throughout the draw cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging if supported and run one full discharge-to-charge cycle before normal use. The phone's fuel gauge IC is calibrated to the old cell's discharge curve — one complete cycle lets it remap against the new cell before reporting accurate percentages.

Why the B200 reports wrong battery percentage after a cell swap

The B200 uses a fuel gauge IC that tracks charge state by measuring voltage curves and accumulated current against a stored cell profile. When a new cell goes in, that stored profile belongs to the old, degraded cell. The IC reads voltage correctly but maps it to the wrong capacity curve, so it can show 80% when the cell is actually at 50%. One full discharge down to automatic shutdown, followed by a complete charge to 100%, forces the IC to rewrite its reference curve against the new cell's actual characteristics.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a short burst of high current and the cell voltage sags below the BMS cutoff threshold — typically around 3.0V — before the fuel gauge catches up. A replacement cell with an uncalibrated coulomb counter makes this worse because the reported percentage does not reflect real charge state. The fix is to complete at least one full discharge-charge cycle so the fuel gauge IC anchors its lower voltage boundary accurately. After calibration, the reported percentage at shutdown should align within a few percent of actual cell depletion.