Vivo Y69 Compatible Battery 3.85V 2900mAh B-C8

Vivo Y69 Series — 3.85V Li-Polymer Replacement Battery (B-C8)

The B-C8 is a 3.85V, 2900mAh Li-Polymer cell for the Vivo Y69, Y69 Dual SIM, Y69 Dual SIM TD-LTE, and model 1714. It replaces the original cell when capacity fade causes noticeably shorter screen-on sessions, unexpected shutdowns, or swollen packaging. Capacity is rated at 11.17Wh to match the original specification.

• Y69 variant compatibility: All four listed models — Y69, Y69 Dual SIM, Y69 Dual SIM TD-LTE, and 1714 — share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One cell fits all four without modification.
• Bench tested on actual hardware: We cycled this cell through charge and load on the Y69 platform and confirmed the BMS accepted the cell, reported state-of-charge correctly after one full cycle, and held voltage above the modem-load cutoff threshold throughout discharge.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging pushes current into an uncalibrated coulomb counter.

Why the Y69 reports wrong battery percentage after a cell swap

The Y69 uses a fuel gauge IC that tracks charge state against a learned discharge curve stored from the old cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry and impedance. The IC reads voltage and translates it to a percentage using the old map — so 70% on screen may be 55% of real capacity. One full discharge-to-charge cycle forces the IC to relearn the curve and sync the coulomb counter to the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff, not a capacity problem. When the modem transmits or the screen brightness peaks, current draw spikes sharply. If the fuel gauge IC is still calibrated to the old cell, it overestimates remaining charge — then the cell voltage drops below the BMS cutoff threshold under that spike load and the phone shuts off immediately. The fix is the same recalibration cycle: discharge to auto-shutdown, charge uninterrupted to 100%, then check that reported percentage tracks evenly down to around 3.5V under load before the next shutdown.