BSQ09 HTC Wildfire E1 Replacement Battery 3.85V 2950mAh

HTC Wildfire E1 / E1 Plus — 3.85V Li-Polymer Replacement Battery (BSQ09)

This is a 3.85V, 2950mAh Li-Polymer cell built to replace the original BSQ09 battery in the HTC Wildfire E1 and Wildfire E1 Plus. Both phones share the same battery bay dimensions and connector pinout, so one part covers both models. At 78.70 × 59.80 × 3.80mm, it sits flush in the chassis without pressure on the rear cover.

• Wildfire E1 and E1 Plus coverage: HTC used the same battery bay, connector, and BMS handshake spec across both Wildfire E1 variants. The voltage rail and physical footprint are identical, so a single BSQ09-spec cell works in either phone without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Wildfire E1 platform. The BMS handshake completed correctly, charge termination triggered at 4.35V, and the protection circuit responded to overcurrent as expected.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the Wildfire E1 after a cell swap

The Wildfire E1's fuel gauge IC retains the discharge curve of the old, degraded cell in its coulomb counter. When a new cell is installed, the IC still applies that stale curve to predict remaining capacity. At around 20–30% reported charge, the new cell's actual open-circuit voltage drops below the threshold the modem and display can sustain under load — and the phone cuts out even though the percentage reading suggests capacity remains. One complete uninterrupted discharge-to-shutdown followed by a full charge resets the coulomb counter to the new cell's actual curve and eliminates these early shutdowns.

Phone warm near the battery during the first charge after replacement

A fresh Li-Polymer cell starts with slightly higher internal impedance than a broken-in cell. On the first charge cycle, the charge IC pushes current into that higher-impedance cell, and some energy dissipates as heat rather than stored charge. This is normal on cycle one and reduces noticeably by cycle three as the cell's impedance drops toward its rated value. If warmth continues beyond the third full charge, check that the rear cover is fully seated — a lifted cover traps heat against the battery. The phone should feel cool to the touch by the fourth cycle.