BA S450 HTC Desire Z Replacement Battery 3.7V 1350mAh

HTC Desire Z / A7272 — 3.7V Li-ion Replacement Battery (BA S450)

This is a 3.7V, 1350mAh Li-ion cell that replaces the original BA S450 in the HTC Desire Z (A7272), Vision, and BB96100 slider Android phones. The original cells in these devices are well over a decade old and commonly hold less than 40% of rated capacity. This replacement restores the phone to factory-spec power delivery.

• Desire Z / Vision / BB96100 platform: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers the entire lineup. The 35H00140-00M and 35H00140-01M part numbers are revision variants of the same BA S450 form factor.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Desire Z platform. The BMS accepted the charge IC handshake without error flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold — no thermal events, no overcurrent trips.
• Fuel gauge recalibration on first use: After installing this cell, disable any fast-charge accessory and run one full discharge-to-charge cycle. The Desire Z fuel gauge IC calibrates against the cell's discharge curve — skip this and the percentage readout will be inaccurate until it completes a full cycle on its own.

Why the Desire Z reports wrong battery percentage after a cell swap

The Desire Z uses a coulomb-counter fuel gauge IC that learns the discharge curve of whichever cell is installed. When you swap in a new cell, the IC still holds the curve data from the old, degraded cell. This mismatch causes the percentage to jump, stall, or report full when the cell is not. One complete discharge cycle — from above 90% down to automatic shutdown — resets the learned curve to match the new cell's actual capacity.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated — it calls 20% remaining, but the cell voltage is already close to the BMS low-voltage cutoff near 3.0V. Under modem or display load, the cell voltage sags quickly past the cutoff threshold and the phone shuts off. Run the calibration cycle described above first. If shutdowns continue after two full cycles, check that the battery connector is fully seated — a partial connection raises contact resistance and accelerates voltage sag under load.