About this replacement
UMI UMIDIGI A9 Pro — 3.85V Li-Polymer Replacement Battery (1ICP/5/65/80)
This is a 3.85V, 3700mAh Li-Polymer battery for the UMIDIGI A9 Pro smartphone. It replaces part number 1ICP/5/65/80 and restores power to the display, processor, and cellular radio. Use it when the original cell no longer holds charge or causes unexpected shutdowns.
- UMIDIGI A9 Pro fit: The A9 Pro uses a 3.85V nominal rail matched to its PMIC. This cell meets that voltage spec and matches the original connector pinout and physical dimensions — 81.30 × 65.20 × 4.20mm — so the BMS handshake with the charge IC completes correctly.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the A9 Pro platform and confirmed BMS communication, charge acceptance, and thermal behaviour under screen-on and modem-active loads. No cutoff anomalies were recorded during the test sequence.
- Fuel gauge recalibration on first use: On first installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This allows the fuel gauge IC to build an accurate discharge curve against the new cell before high-current charging is applied to an uncalibrated coulomb counter.
Sudden shutdown at 20–30% on the UMIDIGI A9 Pro after a cell swap
This happens because the fuel gauge IC is still reading the old cell's voltage curve. The new cell hits a voltage cliff under modem or display load at a state of charge the gauge reads as 20–30%. The phone cuts out because actual cell voltage drops below the PMIC's minimum threshold even though the percentage looks safe. One full discharge-charge cycle at standard rate re-maps the gauge to the new cell's curve and eliminates the cliff.
USB-PD fast charge not triggering after replacement
On the first cycle after installation, the A9 Pro's charge IC may not complete the USB-PD handshake with the new cell's BMS, so the phone accepts only standard 5V charging. This is normal — the BMS and charge IC exchange authentication on first contact and may require one standard charge cycle to settle. After that first full charge at standard rate, reconnect your fast charger and the PD negotiation should complete. If it does not trigger after two full cycles, check that the charge port is clean and the cable supports USB-PD.