C765804220L BLU Win HD Compatible Battery 3.8V 2300mAh

BLU Win HD / W510U Series — 3.8V Li-Polymer Replacement Battery (C765804220L)

This 3.8V, 2300mAh Li-Polymer cell replaces the original C765804220L battery in the BLU Win HD, W510U, Life 8, and L280 smartphones. It restores calling, messaging, and app functionality when the original cell has degraded or failed to hold a charge. Capacity figure is 8.74Wh as rated.

• Win HD / W510U platform fit: These models share the same battery bay dimensions, 3.8V nominal voltage rail, and connector pinout. The BMS handshake on each device accepts this cell's protection circuit without modification or adapter.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a BLU Win HD unit. The BMS accepted the cell on first insertion, protection thresholds tripped correctly at low voltage, and charge current ramped without fault flags.
• 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 map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the start.

Sudden shutdown at 20–30% on the BLU Win HD after a cell swap

A new Li-Polymer cell has a slightly different voltage-versus-capacity curve than the worn cell the fuel gauge IC was calibrated against. When the modem fires during a call or the screen peaks in brightness, load current spikes and the cell voltage briefly dips below the BMS cutoff threshold — even though the gauge still reads 20–30%. The phone shuts down to protect the cell. One full discharge-charge cycle with fast charging off forces the coulomb counter to relearn the new cell's actual voltage floor, and the shutdowns stop.

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

Li-Polymer cells self-discharge in storage, and if the cell voltage drops below roughly 2.5V per cell, the BMS enters lockout mode and blocks all current flow to protect against thermal runaway. Plugging in the charger appears to do nothing — no charging indicator, no boot. Connect the phone to a wall adapter rather than USB-PC, leave it for 15–20 minutes untouched, and the charge IC will trickle enough current through to bring the cell above the BMS re-enable threshold. The phone should then show a charging indicator and boot normally.