About this replacement
Vivo iQOO Neo 855S Racing — 3.85V Li-Polymer Replacement Battery (B-H5)
This is a 3.85V, 4400mAh (16.94Wh) lithium-polymer cell built to replace the original B-H5 battery in the Vivo iQOO Neo 855S Racing. It fits the V1936TL and V1936L variants using the same connector and physical footprint. When the factory cell loses capacity or fails to hold voltage under load, this replaces it.
- iQOO Neo 855S Racing, V1936TL, V1936L: All three model numbers share the same chassis, battery bay dimensions (85.30 × 64.05 × 4.60mm), and BMS handshake protocol — one cell covers the full lineup without modification.
- Bench tested on actual hardware: We ran charge and discharge cycles through a full voltage sweep from 4.35V to 3.0V cutoff. The BMS accepted the cell cleanly, and protection circuits responded correctly at both ends of the curve.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current protocols push significant charge into an uncalibrated cell.
Sudden shutdown at 20–30% after fitting a new cell
This happens when the fuel gauge IC is still referencing the discharge curve of the degraded original cell. The new cell has a steeper voltage cliff at lower states of charge than the old one, so the phone cuts power before the percentage display reaches zero. The Snapdragon 855+ modem and display draw enough current during peak loads to pull cell voltage below the BMS cutoff threshold faster than the gauge expects. One full discharge-charge cycle at standard current resets the coulomb counter and resolves the mismatch.
Fast charge not activating on the first cycle after replacement
Vivo's proprietary fast-charge protocol performs a handshake between the charger IC and the BMS on each new charge session. On a freshly installed cell, the BMS may default to standard 5V charging until it completes an initial calibration pass. Disconnect and reconnect the charger after the phone has been on for two minutes — this re-triggers the handshake. If fast charge still does not activate, complete one full cycle at standard charge current first, then retry with the original Vivo adapter.