About this replacement
Vivo iQOO Z3 / V2073A — 3.87V Li-Polymer Replacement Battery (B-Q1)
This is a 3.87V, 4300mAh (16.64Wh) Li-Polymer cell for the Vivo iQOO Z3 smartphone (model V2073A). It replaces OEM part number B-Q1 and fits the original battery bay without modification. If your iQOO Z3 drains fast, shuts down unexpectedly, or won't hold a charge, this cell restores full function.
- iQOO Z3 and V2073A compatibility: Both model designations use the same B-Q1 cell, share the same connector pinout, and draw from the same charge IC. The BMS handshake is identical across both variants, so no firmware or hardware difference affects fitment.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the iQOO Z3 platform. The BMS accepted the cell without error flags, charge IC stepped through trickle, CC, and CV phases cleanly, and the fuel gauge IC tracked state-of-charge without erratic jumps after the first full cycle.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the coulomb counter recalibrate against the new cell's discharge curve before high-current charging pushes amps into an uncalibrated gauge.
Sudden shutdown at 20–30% on the replacement cell
A new cell has a discharge curve the fuel gauge IC has never seen before. When the phone hits a load spike — 5G modem handoff, screen at full brightness, or a background sync — the cell voltage drops sharply under load, even though the gauge still reads 25%. The protection circuit reads this as a undervoltage event and cuts power before the gauge catches up. One full slow-charge cycle recalibrates the coulomb counter to the new curve. After that cycle, the shutdowns stop because the gauge is now tracking actual cell voltage accurately.
USB-PD fast charge not triggering on the first cycle after installation
After a cell swap, the charge IC on the iQOO Z3 often starts in trickle mode and does not negotiate the fast-charge protocol on the first plug-in. This is because the BMS reports an unverified cell state on first contact, and the charge IC defaults to a conservative current floor. Unplug the cable, wait 10 seconds, and reconnect — this resets the charge IC handshake. If fast charging still does not engage, complete one full standard charge cycle first; the IC will accept the fast-charge protocol once the cell reaches a verified state-of-charge above 3.6V.