About this replacement
Vivo iQOO Neo 9 Pro — 7.89V Li-Polymer Replacement Battery (BA13)
This is a 7.89V, 2500mAh (19.73Wh) Li-Polymer cell for the iQOO Neo 9 Pro smartphone. It fits the Neo 9 Pro directly, matching the OEM BA13 part number. Replace this when the original cell no longer holds usable charge or has swollen past safe operating limits.
- iQOO Neo 9 Pro fitment: The Neo 9 Pro uses a dual-cell Li-Polymer pack wired in series to reach the 7.89V nominal rail. The BA13 matches that series configuration, the flex connector pinout, and the NTC thermistor line the charge IC monitors during fast charging sessions.
- Bench tested on actual hardware: We cycled this cell through the iQOO Neo 9 Pro's charge IC handshake. The BMS accepted the cell without fault flags, the NTC thermistor reading stayed within the charge IC's acceptance window, and voltage under a screen-on modem load held above the low-voltage cutoff threshold.
- First-cycle fast charge protocol: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated cell.
Sudden shutdown at 20–30% on the replacement cell
The iQOO Neo 9 Pro's fuel gauge IC retains the discharge curve from the old, degraded cell. When the new BA13 cell hits a voltage point the IC hasn't mapped correctly, it reports a state-of-charge that's higher than actual. Under modem or display load, the cell voltage drops sharply past the BMS cutoff before the OS gets a low-battery warning. One full uninterrupted discharge-charge cycle without fast charging lets the coulomb counter remap to the new cell's curve. After that cycle, shutdowns at artificially high percentages stop.
USB-PD or proprietary fast charge not triggering after replacement
The iQOO Neo 9 Pro uses a proprietary fast charge protocol that requires the charge IC to verify cell temperature and voltage via the NTC thermistor line before stepping up current. On a freshly installed cell, the thermistor reading can sit outside the IC's learned acceptance window on the first plug-in, so the charger falls back to standard 5V/2A input. Reconnect the charger after the phone has been fully powered on for two minutes — this gives the charge IC time to read a stable thermistor value. If fast charge still doesn't activate, confirm the flex connector is fully seated, as a partial connection breaks the NTC circuit at pin level.