Brondi AMICO COMFORT Replacement Battery 3.7V 900mAh

Brondi AMICO COMFORT Series — 3.7V Li-ion Replacement Battery (KLB423450)

This 3.7V 900mAh Li-ion cell replaces the KLB423450 battery used in the Brondi AMICO COMFORT, AMICO PRATICO, AMICO SINCERO, and AMICO STONE. It restores power to a phone that no longer holds a charge or fails to switch on. Capacity and voltage match the original specification exactly.

• AMICO series compatibility: These models share the same battery bay dimensions (53 × 34 × 4.80mm), voltage rail, and connector pinout. The KLB423450 part number covers all four variants, so one cell fits the full lineup without modification.
• Bench tested on actual hardware: We cycled this cell through full discharge and charge sequences on the AMICO platform. The BMS accepted charge from the phone's onboard charge IC without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100%. The phone's fuel gauge IC is calibrated against the old cell's discharge curve — one full cycle resets it to the new cell so percentage readings stay accurate.

Sudden shutdown at 20–30% on a replacement cell

A new cell with an uncalibrated fuel gauge IC causes this. The phone's software estimates remaining capacity from a stored discharge curve that matched the old, degraded cell — not this one. When the screen or network radio draws current, voltage drops faster than the estimate predicts, and the OS calls a protection shutdown before the gauge catches up. One full discharge-to-shutdown followed by an uninterrupted charge cycle resets the coulomb counter and clears the premature cutoff.

Phone will not power on after the battery sat in storage

Li-ion cells self-discharge in storage. If the cell drops below approximately 2.5V, the BMS enters lockout mode and blocks charge to prevent damage to a deeply discharged cell. Plugging in the charger shows nothing on screen. Leave the charger connected for 20–30 minutes — the charge IC trickle-charges at low current to recover the cell voltage above the BMS re-enable threshold before switching to normal charge current. If the screen remains blank after 30 minutes, check the charger cable is delivering voltage to the port.