Alcatel BH4 OT-535 Replacement Battery 3.7V 750mAh

Alcatel OT-535 / OT-735 Series — 3.7V Li-ion Replacement Battery (BH4)

This is a 3.7V, 750mAh Li-ion cell replacing the original BH4 battery in the Alcatel OT-535, OT-735, OT-556, OT-557, and compatible variants. It fits the same physical bay and uses the same connector pinout as the factory cell. Capacity matches the original spec at 2.78Wh.

• OT-535 / OT-735 platform fit: These models share the same 3.7V single-cell architecture, connector layout, and BMS handshake protocol — one cell covers all listed variants without modification.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on an OT-535 body. The BMS accepted the cell without error flags, charge termination triggered correctly at 4.2V, and protection cutoff engaged at the expected low-voltage threshold.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge to auto-off, then charge uninterrupted to 100% before normal use. The OT-535 fuel gauge IC was calibrated against the old cell's discharge curve — one full cycle resets that baseline against the new cell so percentage readings stay accurate.

Why the OT-535 reports wrong battery percentage after a cell swap

The OT-535 uses a fuel gauge IC that tracks charge state by comparing current discharge behavior against a stored cell curve. When you replace the cell, the IC is still referencing the degraded curve of the old battery. The new cell has a different internal resistance and a steeper voltage-to-capacity relationship, so the IC misreads remaining charge. One full discharge-to-cutoff and uninterrupted recharge forces the IC to rebuild its reference curve against the actual new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a current spike the cell cannot sustain at low state of charge — voltage collapses below the BMS protection threshold and the phone cuts off instantly. It is not a faulty cell; it is the fuel gauge IC firing shutdown based on a misread voltage cliff from an uncalibrated curve. Run one full discharge-to-cutoff cycle immediately after installation. After recalibration, the IC tracks the actual discharge curve and shutdown moves to the correct low-voltage point near 3.4–3.5V per cell.