HTC Ace Replacement Battery BA S470 3.7V 1250mAh

HTC Desire HD / Ace — 3.7V Li-ion Replacement Battery (BA S470)

This 3.7V Li-ion cell at 1250mAh replaces the original battery in the HTC Ace, Desire HD, A9191, and Surround. It fits the same battery bay and uses the same connector as the OEM unit. Voltage and capacity match the original HTC specification exactly.

• Desire HD / Ace platform compatibility: The Ace (A9191) and Desire HD share the same battery bay dimensions, connector pinout, and charge IC handshake. Both draw from the same 3.7V cell architecture, which is why a single part number — BA S470 — covers both devices without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the Desire HD platform. The BMS accepted charge without tripping the over-voltage cutoff, and the phone's charge IC communicated normally throughout the cycle.
• Fuel gauge recalibration on first use: Disable fast charging for your first complete discharge-charge cycle after fitting this cell. The fuel gauge IC on the Desire HD calibrates against the cell's discharge curve on that first pass — running high current into an uncalibrated cell causes the percentage readout to drift for weeks afterward.

Sudden shutdown at 20–30% on the HTC Desire HD after a cell swap

This happens because the Desire HD's fuel gauge IC is still using the discharge curve mapped to the old, degraded cell. The new cell has a steeper voltage drop under modem and screen load than the IC expects. When voltage dips below roughly 3.5V under that load, the phone cuts out even though the reported percentage looks safe. One full discharge-to-shutdown followed by an uninterrupted charge to 100% lets the coulomb counter reset against the new cell's actual curve. After that cycle, shutdowns at false percentages stop.

Phone feels warm near the battery during the first charge after installation

A fresh Li-ion cell has higher internal impedance than a cell that has been through several cycles. The Desire HD's charge IC pushes current into that higher-impedance cell, and the extra resistance converts some of that energy to heat. This is most noticeable in the first one to three charge sessions. If the phone stays warm after the third full charge or gets hot to the touch, check that nothing is blocking ventilation and that the battery contacts are fully seated — a partial connection forces the IC to compensate with elevated current.