About this replacement
UMI UMIDIGI A1 Pro — 3.85V Li-Polymer Replacement Battery (1ICP/5/64/85)
This is a 3.85V, 3000mAh (11.55Wh) Li-Polymer cell replacing part number 1ICP/5/64/85 in the UMIDIGI A1 Pro smartphone. It fits the original battery bay and connects via the stock flex connector. Use the capacity figure above — not third-party listings, which vary.
- UMIDIGI A1 Pro fit: The A1 Pro uses a 3.85V nominal rail with a single-cell Li-Polymer pack at 70.62 × 56.30 × 4.30mm. This cell matches that physical envelope and voltage rail exactly, so the charge IC and BMS handshake proceed without mismatches.
- Bench tested on actual hardware: We cycled this cell through charge and load draws that mirror the A1 Pro's modem, display, and idle states. The BMS held cutoff at the correct low-voltage threshold and accepted charge termination without error flags.
- Fuel gauge recalibration after install: On first use after fitting this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge to 100% uninterrupted. This lets the A1 Pro's fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins.
Why the UMIDIGI A1 Pro reports wrong battery percentage after a cell swap
The A1 Pro's fuel gauge IC stores a learned discharge curve from the original cell. When you install a new cell, that stored curve no longer matches actual cell behaviour. The gauge reads voltage and applies the old curve, so the percentage shown can be off by 10–20% in either direction. One complete discharge-charge cycle with no interruptions forces the IC to relearn the new cell's voltage-to-capacity relationship and restores accurate readings.
Sudden shutdown at 20–30% on the replacement cell
This happens when the modem or display pulls a brief high-current spike and the cell voltage drops below the BMS cutoff threshold faster than the fuel gauge expects. A new cell has higher internal impedance than a settled one, which makes voltage sag under load more pronounced in the first few cycles. The phone interprets the voltage cliff as a dead cell and shuts down even though the gauge shows charge remaining. After three to five full discharge-charge cycles, internal impedance drops and the shutdowns stop — no replacement needed.