UMIDIGI A7s Compatible Battery 3.85V 4050mAh 1ICP/5/63/80

UMI UMIDIGI A7s — 3.85V Li-Polymer Replacement Battery (1ICP/5/63/80)

This is a 3.85V, 4050mAh Li-Polymer cell for the UMIDIGI A7s smartphone. It replaces the original OEM battery when capacity fade makes the phone unreliable through a full day. Direct fit for the A7s chassis — 79.20 x 61.70 x 4.50mm, matching the OEM envelope exactly.

• UMIDIGI A7s fit: The A7s uses a single-cell Li-Polymer pack at 3.85V nominal. The connector pinout and BMS handshake match the fuel gauge IC on the A7s board — the phone reads state-of-charge from the same signal lines as the original cell.
• Bench tested on actual hardware: We cycled this cell through full discharge-charge sequences on the A7s board, confirmed the BMS accepted the cell without fault flags, and verified the fuel gauge IC tracked voltage across the full discharge curve without dropping into lockout.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the charge IC pushes high current into an uncalibrated pack — the A7s fuel gauge needs a clean reference cycle or it will read percentage inaccurately from the start.

Sudden shutdown at 20–30% on the UMIDIGI A7s

The A7s modem and display draw sharp current spikes that cause a weakened cell's terminal voltage to sag below the BMS cutoff threshold — even when the fuel gauge still shows charge remaining. A fresh cell with full capacity won't sag under that load, but the fuel gauge IC must first be calibrated to the new cell's voltage-versus-capacity curve. Until that calibration cycle runs, the phone can misread the state-of-charge and cut power earlier than the actual remaining capacity warrants. Run one full discharge to automatic shutdown, then charge uninterrupted to 100% before resuming normal use. After that cycle, the fuel gauge recalibrates and shutdown-under-load behaviour normalises.

USB fast charge not activating after battery replacement

On the first charge cycle after a cell swap, the A7s charge IC sometimes defaults to standard 5V charging rather than negotiating fast charge protocol. This happens because the BMS presents different impedance on a new cell versus a cycled one, and the charge IC uses that impedance reading during handshake. It is not a fault with the replacement cell. Charge the phone once at standard current using a basic 5V charger, let it reach 100%, then reconnect your fast charger — the IC renegotiates the protocol correctly on the second cycle.