BBK i267 BK-BL-4C Replacement Battery 3.7V 750mAh

BBK i267 / i508 / i509 / i518 Series — 3.7V Li-ion Replacement Battery (BK-BL-4C)

This is a 3.7V Li-ion cell rated at 750mAh (2.78Wh), replacing OEM part BK-BL-4C across the BBK i267, i508, i509, i518, and compatible models. It restores power to the handset when the original cell has degraded, swollen, or stopped holding a charge. Dimensions are 53.00 × 34.00 × 4.80mm — verify against your existing cell before fitting.

• Multi-model fit — i267 through i518 series: These BBK handsets share the same battery bay dimensions, connector pinout, and BMS handshake protocol, which is why a single cell covers the range. The charge IC in each model expects the same 3.7V nominal, 4.2V charge ceiling, and 2.75V cutoff floor.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on BBK-compatible test rigs. The BMS engaged cutoff correctly at low voltage and accepted the full charge cycle without triggering protection flags at rated current.
• Fuel gauge recalibration on first install: On first use after fitting, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the OS begins drawing on coulomb-counter data for percentage reporting.

Sudden shutdown at 20–30% on the BBK i267 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 the IC wasn't expecting at that state-of-charge, it misreads remaining capacity. Under modem or screen load, the voltage drops sharply — the IC sees it as a cliff and the phone shuts off. Run one full discharge to near-zero, then charge uninterrupted to 100% at standard rate. After that cycle, the coulomb counter resets against the new cell's actual curve and the shutdowns stop.

Phone won't power on after the replacement cell sat in storage

Li-ion cells self-discharge during storage. If the cell voltage has dropped below roughly 2.5V, the BMS enters lockout mode and blocks current flow to protect the cell from deep-discharge damage. The phone shows nothing — no charging animation, no response. Connect it to a wall charger rated at the original spec and leave it for 15–20 minutes without pressing any buttons. Most BMS circuits on this platform will accept a trickle-recovery charge once the cell climbs back above 2.75V and will then allow normal boot.