About this replacement
BLU Win HD 5.5" / X150 Series — 3.8V Li-Polymer Replacement Battery (C806003250L)
This is a 3.8V, 2500mAh Li-Polymer battery for the BLU Win HD 5.5", X150Q, and X150 smartphones. It replaces part number C806003250L. Use it when the original cell no longer holds a usable charge or causes unexpected shutdowns.
- Win HD 5.5" / X150 platform fit: The X150 and X150Q share the same battery bay dimensions and connector pinout. All three models pull from the same 3.8V nominal rail, and the BMS handshake is consistent across the family — one cell covers the full range.
- Bench tested on actual hardware: We ran this cell through full charge and load cycles on the Win HD 5.5" platform. The BMS accepted the charge IC handshake on the first cycle, and protection cutoffs triggered correctly at both ends of the voltage range.
- Fuel gauge recalibration after swap: After fitting this cell, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated register — reducing percentage jumps in the first few days of use.
Why the Win HD 5.5" reports wrong battery percentage after a cell swap
The fuel gauge IC on the Win HD 5.5" uses a coulomb counter that was calibrated to the original cell's discharge curve. When you fit a new cell, those stored values no longer match the actual charge state. The phone may show 40% and shut off, or sit at 100% longer than expected. One full discharge to shutdown followed by an uninterrupted charge to 100% resets the counter. After that single cycle, percentage reporting stabilises.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under load — typically when the modem fires up for a call or the display hits full brightness. A Li-Polymer cell that reads 3.6V at rest can sag below the 3.2V cutoff threshold instantly under that current draw, triggering a hard shutdown even though the gauge still shows charge remaining. It is not a faulty cell — it is the fuel gauge IC reporting from stale calibration data. Run one full discharge-charge cycle and confirm the cell rests at 3.8V–4.2V at top of charge before concluding there is a deeper fault.