Doro DBM-1500B Liberto 820 Mini Replacement Battery 3.7V 1500mAh

Doro Liberto 820 mini — 3.7V Li-ion Replacement Battery (DBM-1500B)

This is a 3.7V Li-ion replacement battery rated at 1500mAh (5.55Wh) for the Doro Liberto 820 mini and 6778. It replaces OEM part number DBM-1500B. The Liberto 820 mini is a senior-focused smartphone, so restoring a stable, predictable power supply matters more here than on a typical handset.

• Liberto 820 mini and 6778 compatibility: Both models use the same battery bay dimensions (51.30 × 51.10 × 5.50mm), the same 3.7V nominal voltage rail, and the same connector pinout. One replacement cell covers both variants without modification.
• Bench tested on actual hardware: We cycled this cell on the Liberto 820 mini and confirmed the BMS handshake completed correctly. Charge acceptance was normal across a full discharge-charge cycle. No thermal flags or cutoff events were triggered at any state of charge.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if the option appears and run one complete discharge-charge cycle. The phone's fuel gauge IC was calibrated against the old cell's discharge curve. One full cycle lets it recalibrate against the new cell before reporting accurate percentages.

Sudden shutdown at 20–30% on the Liberto 820 mini after a cell swap

A new cell has a slightly different internal resistance profile than the depleted original. At 20–30% state of charge, the modem radio or display backlight pulls a short high-current spike. If the fuel gauge IC still expects the old cell's voltage curve, it allows discharge into a range where the new cell cannot sustain voltage under that load. The result is an abrupt shutdown even though the on-screen percentage still shows charge remaining. One full discharge-charge cycle resets the coulomb counter and maps the new cell's actual voltage cliff, pushing the safe cutoff threshold to the correct point.

Phone not turning on after the replacement battery sat in storage

Li-ion cells self-discharge in storage. If this battery dropped below approximately 2.5V per cell before fitting, the BMS will lock out charging as a protection measure against plating lithium onto the anode. The phone will show no charge indicator and will not power on. Connect the device to a wall charger — not a USB hub or laptop port — and leave it undisturbed for 15–30 minutes. Most BMS circuits include a trickle pre-charge mode that slowly raises the cell voltage back above the 2.5V threshold before allowing full charge current to resume.