Olympia Classic Mini II MT433450 Replacement Battery 3.7V 700mAh

Olympia Classic Mini II — 3.7V Li-ion Replacement Battery (MT433450)

This is a 3.7V 700mAh Li-ion replacement battery for the Olympia Classic Mini II mobile phone. It fits the MT433450 slot directly and restores power once the original cell degrades below usable capacity. Voltage and capacity match the original spec exactly.

• Classic Mini II cell specification: The Classic Mini II uses a compact Li-ion cell on a 3.7V nominal rail. The MT433450 part number identifies a specific cell footprint and connector pinout — this replacement matches both, so the BMS handshake completes without fault codes.
• Bench tested on actual hardware: We cycled this cell through full charge-to-cutoff runs on the Classic Mini II platform. The BMS accepted the cell, charge termination triggered correctly at 4.2V, and the protection circuit tripped within spec on an intentional over-discharge test.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging if your charger supports it and run one complete discharge-to-charge cycle. The fuel gauge IC on the Classic Mini II calibrates its coulomb counter against the new cell's discharge curve — skipping this step causes percentage readings to drift or jump in the first few days of use.

Sudden shutdown at 20–30% on the Classic Mini II

This is a voltage cliff failure, not a capacity fault. When the modem transmits or the screen peaks, the cell must deliver a short current burst. An aged or uncalibrated cell drops below the BMS cutoff threshold under that load even when the fuel gauge still shows charge remaining. On the Classic Mini II, this typically happens when the resting voltage under no load reads around 3.6–3.7V but sags below 3.2V the moment the radio fires. Replacing the cell and completing one full calibration cycle eliminates the sag in a new cell and resets the gauge baseline.

Phone won't power on after sitting in storage

Li-ion cells stored in a discharged state can drop below 2.5V per cell, which triggers the BMS protection circuit into lockout mode. The Classic Mini II will show nothing on screen — no charging indicator, no boot attempt. Connect it to a wall charger rather than a USB port for the first 15–30 minutes to push enough trickle current past the BMS lockout threshold. Once the cell recovers to approximately 3.0V, the BMS re-initialises and normal charging resumes.