Asus ZenFone Go 4.5 B11P1428 Replacement Battery 3.85V 2050mAh

Asus ZenFone Go 4.5 / ZB452KG — 3.85V Li-ion Replacement Battery (B11P1428)

This is a 3.85V, 2050mAh (7.89Wh) Li-ion cell for the Asus ZenFone Go 4.5 (ZB452KG / X009DB). It matches OEM part number B11P1428 and fits directly into the battery bay without modification. The cell ships with a partial charge, as is standard for Li-ion transport.

• ZB452KG and X009DB compatibility: Both model variants use the same 3.85V single-cell architecture with the same connector pinout and BMS handshake protocol. Swapping between these variants does not require any firmware change or hardware adaptation.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on a ZB452KG unit. The BMS accepted the cell without rejecting the charge IC handshake, and the fuel gauge IC began tracking state-of-charge correctly after one complete cycle.
• Fuel gauge recalibration after install: On first use, disable fast charging and run one complete discharge down to automatic shutdown, then charge to 100% uninterrupted. This allows the fuel gauge IC to map its coulomb counter against the new cell's actual discharge curve before high-current charging begins.

Sudden shutdown at 20–30% on a replacement cell in the ZB452KG

The ZenFone Go 4.5 uses a single-cell 3.85V configuration with no cell balancing. When the modem and display draw simultaneous load peaks, the cell voltage can sag sharply below the BMS protection threshold even if the fuel gauge still reads 20–30%. This happens because the fuel gauge IC is still calibrated to the old cell's internal resistance curve. After one full discharge-charge cycle, the coulomb counter resets its model to the new cell, and the sag-triggered shutdowns stop.

Phone not powering on after the replacement cell sat in storage

If this battery was stored in a discharged state for an extended period, the cell voltage may have dropped below 2.5V — the BMS lockout threshold. At that voltage the BMS opens its protection circuit and blocks all charge input to prevent thermal runaway. Connect the phone to a wall charger for at least 15–20 minutes without pressing the power button; the charge IC applies a trickle current that slowly recovers the cell voltage back above the 2.8V re-enable threshold. Once the BMS re-initialises, normal charging resumes automatically.