HTC Desire Z Replacement Battery BA S450 3.7V 1000mAh

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

This is a 3.7V 1000mAh Li-ion cell for the HTC Desire Z (A7272), also sold as the HTC Vision and BB96100. It slots into the same battery bay as the original BA S450 and shares the same connector pinout. Fits the full Desire Z family using the 35H00140-00M and 35H00140-01M part numbers.

• Desire Z / Vision platform fit: These models run the same 3.7V power rail and use an identical three-pin connector with a shared BMS handshake protocol — one cell covers the entire range without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Desire Z unit. The BMS accepted charge from the onboard charge IC without fault flags and held voltage above 3.5V through the full discharge curve under mixed screen and radio load.
• Fuel gauge recalibration on first use: On first installation, run the phone from 100% down to automatic shutdown, then charge uninterrupted to full. This gives the fuel gauge IC one complete reference cycle against the new cell before the OS starts reporting percentages — skipping this step is the main cause of erratic percentage readings after a cell swap.

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

The Desire Z uses a fuel gauge IC that builds its charge model around the discharge curve of the cell it first learned on. Swap in a new cell and the IC is still referencing the old curve — typically an aged cell with higher internal resistance and a steeper voltage drop. The result is a mismatch between the displayed percentage and actual state of charge. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and gives the IC a clean curve to map against.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem fires a high-current burst — during a call, data sync, or Wi-Fi scan — and the cell voltage dips below the BMS cutoff threshold even though the displayed percentage looks fine. On a new cell, this is almost always a fuel gauge calibration problem rather than a faulty cell. The IC still thinks it's working with the old cell's voltage floor and cuts power too early. Do the full recalibration cycle first; if shutdown still occurs below 3.5V under load after two full cycles, check that the battery contacts are clean and making firm contact.