About this replacement
BBK VIVO Y20 Series — 3.8V Li-Polymer Replacement Battery (BK-B-68)
This is a 3.8V, 2500mAh (9.5Wh) lithium-polymer cell replacing part number BK-B-68 in the VIVO Y20, Y20W, and Y20T. The original cell degrades over charge cycles, causing the phone to shut down early or fail to hold a charge. This replacement restores the battery bay to factory capacity.
- VIVO Y20, Y20W, Y20T compatibility: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 93.47 × 58.07 × 3.41mm cell fits the chassis without modification, and the charge IC on each variant accepts the same BMS communication.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a VIVO Y20 unit. The BMS accepted the cell without error flags, and the charge IC completed CC/CV charging without cutoff anomalies or temperature fault triggers.
- 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 against the new cell's discharge curve before the charge IC pushes high current into an uncalibrated cell.
Sudden shutdown at 20–30% on the VIVO Y20 after a cell swap
The VIVO Y20's fuel gauge IC builds a discharge model based on the old cell's internal resistance profile. A new cell has a different voltage-versus-capacity curve, so the IC misreads remaining capacity and reports 20–30% when the cell is already near its cutoff voltage. Under modem transmit or display brightness load, the cell voltage drops below the BMS threshold instantly and the phone shuts off. One full discharge-charge cycle without fast charging forces the coulomb counter to resync to the new cell's actual curve.
Phone warm near the battery compartment during the first few charges
A fresh lithium-polymer cell has slightly higher internal impedance than a broken-in cell. During the first two or three charges, the charge IC converts more energy to heat as it pushes current through that higher impedance. This is normal and reduces as the cell cycles. If warmth persists beyond the third charge cycle or the phone becomes hot to the touch, check that the back cover is fully seated — a lifted cover traps heat directly against the cell.