About this replacement
ZTE Blade A5 2020 / Visible R2 — 3.85V Li-Polymer Replacement Battery (Li3931T44P8h806139)
This is a 3.85V, 3100mAh Li-Polymer cell built to replace the original battery in the ZTE Blade A5 2020, Visible R2, Z5151V, and Blade A7 Prime, among other compatible models. It targets phones where the original cell no longer holds adequate charge or has failed outright. Capacity is 11.94Wh — matched to OEM part Li3931T44P8h806139.
- Cross-model fit on the A5 2020 platform: The Blade A5 2020, Visible R2, and Z5151V share the same battery bay dimensions, connector pinout, and BMS handshake protocol — that is why one cell covers all three. The 78.76 × 60.70 × 3.60mm footprint is fixed across this platform.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Blade A5 2020 unit. The BMS accepted the cell without fault codes, and the charge IC completed a full cycle to 4.35V cutoff without thermal interruption.
- Fuel gauge recalibration after installation: On first use, disable fast charging and run one complete discharge-to-charge cycle at standard current. This allows the fuel gauge IC to recalibrate its discharge curve against the new cell before high-current charging begins on an uncalibrated coulomb counter.
Sudden shutdown at 20–30% on the Blade A5 2020
This happens when the fuel gauge IC is still mapped to the old cell's discharge curve. The phone reads 25% but the new cell's actual voltage under modem and screen load drops sharply — the BMS cuts power before the gauge catches up. It is not a defective cell. Run one full discharge cycle without fast charging, and the coulomb counter will remap to the new cell's voltage cliff. After that cycle, shutdowns at 20–30% stop on correctly functioning cells.
Phone will not power on after the replacement cell sat in storage
Li-Polymer cells ship in a partial state of charge, typically around 30–40%. If the phone sat unused after installation, the cell may have self-discharged below the BMS lockout threshold — usually 2.5V per cell. The BMS enters a protective lockout and the phone will not respond to the power button. Connect the phone to a wall charger — not a PC USB port — and leave it for 20–30 minutes before attempting to power on. If the cell has not dropped below the hard lockout floor, the charge IC will recover it and the phone will boot normally.