ITT Easymax BL666 Replacement Battery 3.7V 1050mAh

ITT Easymax — 3.7V Li-ion Replacement Battery (BL666)

This is a 3.7V, 1050mAh Li-ion cell for the ITT Easymax smartphone. It replaces part number BL666 when the original cell can no longer hold a charge or has failed completely. Voltage and physical dimensions match the original slot: 53.00 × 33.90 × 5.60mm.

• Easymax platform fit: The Easymax uses a single-cell 3.7V nominal architecture with a dedicated charge IC on the main board. This cell matches that voltage rail and connector pinout, so the board's charge IC communicates with the replacement BMS without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Easymax platform and confirmed the BMS handshake completed correctly. The charge IC accepted the cell without throwing a fault, and the protection circuit tripped cleanly at the expected low-voltage cutoff.
• First-cycle fuel gauge reset: On first use after fitting, disable fast charging if your carrier or app allows it, then run one full 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 state.

Sudden shutdown at 20–30% on the Easymax after a cell swap

A new cell has a slightly different voltage-to-capacity curve than the aged cell the fuel gauge IC was calibrated against. When the modem fires up for a call or the screen hits full brightness, it pulls a current spike the cell can sustain — but the reported 20–30% figure is wrong. The real state of charge is already near the protection cutoff, so the BMS trips and the phone shuts down. One full discharge-to-charge cycle recalibrates the coulomb counter against the actual new cell curve. After that cycle, the percentage readings stabilise.

USB charging not recognised on the first connection after replacement

When a new cell sits below roughly 3.0V from storage, the BMS may not present the expected handshake signal to the phone's charge IC on first plug-in. The phone sees a connected cable but registers no charging current. Connect the phone to a low-current USB source — a standard 5V 500mA port rather than a fast charger — for 10–15 minutes to bring the cell above the BMS re-engagement threshold of approximately 2.9–3.0V per cell. Once the BMS exits lockout, normal charging resumes and a fast charger will be recognised.