BBK V205 Replacement Battery BK-BL-4C 3.7V 900mAh

BBK V205 / i531 / V206 Series — 3.7V Li-ion Replacement Battery (BK-BL-4C)

This is a 3.7V, 900mAh Li-ion cell built to the BK-BL-4C specification. It fits the BBK V205, i531, i606, V206, and five additional BBK mobile handsets that share the same connector and voltage rail. Capacity figure is taken directly from the product data — 900mAh, 3.33Wh.

• Multi-model fit — V205, i531, i606, V206: These BBK handsets share the same physical footprint, contact layout, and 3.7V nominal rail, so a single BK-BL-4C cell covers the group without modification or adapter.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a BBK-compatible test rig. The BMS held cutoff cleanly at the upper voltage limit and did not trip on a standard 500mA charge current.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the OS starts reading state-of-charge from it.

Why the V205 reports wrong battery percentage after a cell swap

The fuel gauge IC on BBK handsets stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry, so the percentage reading drifts. The OS reads state-of-charge from the coulomb counter, which is still calibrated to the old cell's internal resistance profile. One full discharge down to automatic shutdown followed by a full charge to 100% forces the IC to rewrite its reference curve. After that single cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% remaining on the replacement cell

This is a voltage cliff, not a capacity fault. Under modem or screen load, the new cell's voltage drops faster than the fuel gauge IC expects, crossing the hardware cutoff threshold before the display reads zero. It happens most often in the first few cycles when the IC is still using the old cell's voltage-to-capacity map. Run two full discharge-charge cycles without fast charging to give the coulomb counter enough data to recalibrate. If shutdowns continue past three cycles, check that resting cell voltage reads at least 3.7V with a multimeter after a full charge.