Mitsubishi M720 Replacement Battery 3.7V 550mAh Li-ion

Mitsubishi M720 / M750 Series — 3.7V Li-ion Replacement Battery

This 3.7V, 550mAh Li-ion cell replaces the original battery in the Mitsubishi M720, M750, DO13, and M341i mobile phones. It matches the original's physical footprint at 46.02 × 38.51 × 5.56mm and slots directly into the battery bay without modification. Voltage and capacity figures come from the product data, not estimated equivalents.

• M720, M750, DO13, M341i compatibility: These four models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. A single cell works across all four because the BMS communication protocol and charge IC requirements are consistent within this Mitsubishi handset family.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the M720 platform. The BMS accepted the cell without fault codes, charge termination triggered correctly at full voltage, and the protection circuit tripped as expected under short-circuit simulation.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes into an uncalibrated cell — preventing erratic percentage readings from the first day.

Sudden shutdown at 20–30% on the replacement cell

A new Li-ion cell has a slightly different discharge curve than the worn cell it replaces. The phone's fuel gauge IC was calibrated to the old cell's curve, so it misjudges the remaining charge on the new one. Under modem load or screen-on draw, the cell voltage drops faster than the IC expects, and the phone shuts down before the displayed percentage reaches zero. One full discharge-charge cycle with fast charging disabled resets the coulomb counter and eliminates the premature cutoff.

Device not powering on after the replacement cell sat in storage

If the replacement cell was stored for an extended period before installation, it may have self-discharged below 2.5V — the threshold at which the BMS enters lockout to prevent cell damage. The phone will show no response when the power button is pressed. Connect the handset to a charger and leave it for 15–20 minutes without pressing anything; the charge IC will trickle-charge the cell back above the BMS re-enable threshold, after which normal charging and power-on behaviour resumes. If the cell recovers to 3.0V or above, the BMS unlocks and the phone boots normally.