EBA-140 BenQ-Siemens EL71 Replacement Battery 3.7V 600mAh

BenQ-Siemens EL71 — 3.7V Li-ion Replacement Battery (EBA-140)

This is a 3.7V, 600mAh Li-ion cell built to fit the BenQ-Siemens EL71 mobile phone. It replaces the original EBA-140 (also listed as V30145-K1310-X393) when the aged cell can no longer hold adequate charge. Matches the OEM footprint at 38 × 25 × 7mm for direct installation.

• EL71 and EL-71 fitment: Both model designations refer to the same mid-2000s BenQ-Siemens handset. The connector pinout, BMS handshake voltage, and physical envelope are identical across both variants — one cell fits all.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the EL71 platform. The BMS accepted the new cell without fault flags, and the protection circuit responded correctly at both the low-voltage cutoff and top-of-charge termination points.
• Fuel gauge recalibration on first cycle: After fitting this cell, disable any fast-charge accessory and run one full discharge-to-charge cycle at standard current. The EL71's fuel gauge IC was calibrated to the old cell's discharge curve — one complete cycle lets it map the new cell's actual capacity before reporting accurate percentages.

Why the EL71 reports wrong battery percentage after a cell swap

The EL71 tracks charge state using a fuel gauge IC that builds its model from the previous cell's discharge curve. A new cell has a different internal impedance and a slightly different voltage-versus-capacity slope. Until the IC recalibrates, the percentage display lags behind or jumps. One complete discharge from 100% down to auto-shutoff, then a full charge to 4.2V, resets the coulomb counter to the new cell's actual curve.

Sudden shutdown at 20–30% on the replacement cell

This happens when the screen backlight or GSM radio pulls a brief high-current spike and the cell voltage drops below the BMS cutoff threshold — even though the gauge still reads 20–30%. It is a calibration artifact, not a faulty cell. The fuel gauge IC is using the old cell's voltage cliff as its reference point and cutting power too early. Run two full discharge-charge cycles at standard current and the shutdowns should stop as the gauge reanchors to the new cell's actual 3.0V floor.