BBK VIVO Y50 Replacement Battery 3.85V 4800mAh

BBK Vivo Y50 / 1935 — 3.85V Li-Polymer Replacement Battery

This is a 3.85V, 4800mAh Li-Polymer replacement battery for the Vivo Y50 (model 1935). It replaces a degraded or failed original cell and restores power to the device's processor, display, and wireless radios. Dimensions are 88.10 × 63.55 × 4.85mm — confirm your existing cell matches before fitting.

• Vivo Y50 / 1935 compatibility: Both the Y50 and its internal board designation 1935 share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell fits both references without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and load discharge on a Y50 unit. The BMS accepted charge current without fault flags, and the protection circuit tripped correctly at low-voltage threshold — no thermal runaway events across the test run.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter starts reporting to the OS — skipping this step causes erratic percentage readings in the first few days.

Sudden shutdown at 20–30% on the Vivo Y50 after a cell swap

This happens because the fuel gauge IC still holds the discharge curve of the old, degraded cell. When the new cell hits a voltage point the IC wasn't expecting, it interprets remaining capacity incorrectly. Under high-draw moments — mobile data, screen at full brightness, GPS active — the actual cell voltage drops faster than the reported percentage suggests. The fix is one full discharge to auto-off followed by a full uninterrupted charge, which forces the coulomb counter to resync to the new cell's actual voltage floor.

USB-PD or Vivo FlashCharge not activating on the replacement cell's first cycle

Fast charging protocols on the Y50 require a handshake between the charge IC and the battery's BMS before elevated current is allowed. On a fresh cell, the BMS often defaults to slow-charge mode on the first cycle as a protection measure — this is normal behaviour, not a fault. Plug into the original Vivo charger and cable, not a third-party adapter, and let the first cycle complete at standard rate. Fast charging typically activates from the second cycle onward once the BMS clears its initial check.