ZTE Blade A7s Replacement Battery 3.8V 3900mAh Li3839T43P8H826348

ZTE Blade A7s / A7 2020 — 3.8V Li-Polymer Replacement Battery (Li3839T43P8H826348)

This is a 3900mAh (14.82Wh) Li-Polymer cell at 3.8V nominal, built to replace the original battery in the ZTE Blade A7s, Blade A7 2020, A7010, and EA72020. It restores power to the processor, display, and cellular radio when the factory cell no longer holds charge. Voltage and dimensions match OEM spec: 81.00 × 62.70 × 4.80mm.

• A7s / A7 2020 compatibility: The A7010 and EA72020 share the same battery bay dimensions, connector pinout, and 3.8V charge termination voltage as the Blade A7s — one cell covers all four variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Blade A7 2020 platform. The BMS accepted full charge without triggering thermal cutoff, and the fuel gauge IC tracked state of charge accurately after one full calibration cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state — preventing erratic percentage readings from the first day.

Why the Blade A7s reports wrong battery percentage after a cell swap

The fuel gauge IC on the A7s uses a coulomb counter calibrated to the original cell's impedance and discharge curve. When a new cell goes in, that stored profile no longer matches the actual chemistry. The gauge reads voltage against the old curve, so it shows 80% when the real state of charge is 65% — or higher. One full slow discharge from 100% to automatic shutdown, followed by a full charge to 100%, resets the counter against the new cell and brings the percentage display back into alignment.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display fires a high-current draw and the cell voltage drops below the BMS cutoff threshold — even though the gauge still shows charge remaining. On a fresh cell with an uncalibrated fuel gauge, the voltage cliff appears earlier than the percentage suggests. The phone cuts power to protect the cell before the displayed percentage reaches zero. Run two full slow charge-discharge cycles without fast charging, then check whether the shutdowns stop — after calibration, the gauge tracks the cliff accurately and the problem resolves.