Vivo IQOO 8 B-R8 Replacement Battery 7.74V 2150mAh

Vivo IQOO 8 Series — 7.74V Li-Polymer Replacement Battery (B-R8)

This 7.74V, 2150mAh Li-Polymer cell replaces the original B-R8 battery in the Vivo IQOO 8, IQOO 8 5G, and V2136A. It restores full device function — processor, display, 5G modem, and all onboard systems. Dimensions are 83.30 x 63.50 x 5.60mm, matching the original footprint.

• IQOO 8 and V2136A compatibility: These three models share the same battery bay geometry, connector pinout, and BMS handshake protocol. The B-R8 part number covers all three — no adapter or modification needed.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the IQOO 8 platform. The BMS accepted the new cell without error flags, and the charge IC held within spec across both standard and fast-charge current profiles.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's actual discharge curve before high-current fast charging pushes current into an uncalibrated state. Skip this step and percentage readings will drift.

Sudden shutdown at 20–30% on a replacement cell

The IQOO 8's fuel gauge IC stores a charge curve calibrated to the original cell. A new cell with a different internal resistance profile hits a voltage cliff at a different state of charge than the stored curve expects. Under high load — 5G modem activity or display at full brightness — the cell voltage drops faster than the IC predicts, and the phone cuts power before the reported percentage reaches zero. One full discharge-charge cycle with fast charging disabled resets the coulomb counter against the new cell's actual curve. After that cycle, shutdowns at 20–30% stop.

USB-PD fast charge not triggering on first cycle after a cell swap

The IQOO 8 charge IC checks BMS cell voltage before handing off to the fast-charge protocol. On a new cell fresh from storage, resting voltage is typically around 3.7–3.8V per cell — within spec, but the IC may treat the uncalibrated cell as an edge case and fall back to standard 5V charging. This is not a fault with the battery or charger. Letting the phone complete one full standard charge cycle re-establishes the handshake, and fast charging resumes on the next plug-in. Confirm fast charge is active by checking the lock screen indicator — it should read "Flash Charging" at 5V/4A or higher.