Huawei STG-LX1 Replacement Battery 3.91V 6900mAh

Huawei STG-LX1 / Nova Y91 4G — 3.91V Li-Polymer Replacement Battery (HB5470A3EHW-12)

This is a 3.91V, 6900mAh Li-Polymer replacement cell for the Huawei STG-LX1, STG-LX2, Nova Y91 4G, and Changxiang 60X. It carries OEM part number HB5470A3EHW-12 and fits the full STG/Nova Y91 4G platform sharing that connector and BMS handshake. Capacity is 6900mAh (26.98Wh) — matched to the original specification.

• STG-LX1, STG-LX2, Nova Y91 4G platform fit: These models share the same voltage rail at 3.91V nominal, the same flex-connector pinout, and the same BMS communication protocol — one cell covers the full group without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the STG-LX1 platform. The BMS accepted the cell on the first connection, charge termination triggered correctly at full voltage, and protection cutoffs fired at the expected thresholds under load.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-charge cycle at standard rate. The fuel gauge IC in the STG-LX1 is calibrated to the old cell's discharge curve — running one full cycle at low current lets the coulomb counter reset its reference before high-current charging begins.

Sudden shutdown at 20–30% on the Nova Y91 4G after a cell swap

This happens because the fuel gauge IC is still using the discharge curve from the old, degraded cell. The new cell has a steeper voltage cliff at low state-of-charge, so the phone hits undervoltage cutoff well before the gauge reads zero. The BMS shuts the device down to protect the cell, even though the displayed percentage says there's charge remaining. Run two full discharge-charge cycles without fast charging — by the second cycle, the coulomb counter will have mapped the new cell's actual curve and the shutdowns will stop.

STG-LX1 reporting wrong battery percentage after replacement

The percentage readout is driven by the fuel gauge IC, which learned its calibration data from the original cell over months of use. A fresh cell has different internal resistance and a different discharge slope, so the IC's stored model no longer matches reality. You'll see the percentage jump, stall, or drop suddenly — especially below 40%. Fully discharge the phone until it powers off automatically, then charge uninterrupted to 100% at standard rate; repeat once more and the gauge IC will have enough data to recalibrate to the new cell.