Asus Zenfone C B11P1421 Replacement Battery 3.8V 2150mAh

Asus Zenfone C ZC451CG — 3.8V Li-ion Replacement Battery (B11P1421)

This 3.8V, 2150mAh Li-ion cell replaces the original B11P1421 battery in the Asus Zenfone C (ZC451CG, Z007). It fits the standard battery bay and connects to the same flex cable and charge IC as the factory unit. Voltage and capacity match OEM specs exactly — no modifications needed.

• ZC451CG and Z007 compatibility: Both model numbers reference the same hardware platform — identical battery bay dimensions (59.82 × 53.34 × 5.30 mm), the same 3.8V charge rail, and the same BMS handshake with the Zenfone C's charge IC. One cell covers both variants.
• Bench tested on actual hardware: We cycled this cell through a full discharge-charge sequence on the ZC451CG. The BMS accepted the charge IC handshake without fault codes, and protection circuits triggered correctly at both high-current and trickle-charge thresholds.
• Fuel gauge recalibration after install: After fitting this cell, disable fast charging and run one complete discharge down to auto-shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC one clean cycle to map the new cell's discharge curve before high-current charging resumes.

Sudden shutdown at 20–30% on the Zenfone C after a cell swap

The Zenfone C's fuel gauge IC holds a learned discharge curve from the old cell. A new cell has a different internal resistance profile, so the IC misreads remaining capacity and triggers shutdown before the cell is actually depleted. This is a calibration gap, not a fault with the replacement battery. One full discharge-to-shutdown followed by a complete uninterrupted charge resets the coulomb counter and eliminates premature cutoffs. After that cycle, the percentage readout stabilises.

Phone stays on the Asus logo after replacement — won't boot

If a replacement cell has sat in storage, its voltage may have dropped below the BMS lockout threshold — typically under 2.5V per cell — which causes the phone to stall at the boot logo or refuse to power on at all. Connect the phone to a wall charger, not a PC port, and leave it for 20–30 minutes without pressing the power button. A PC USB port often can't supply enough current to wake a locked-out BMS. Once the charge IC detects a rising cell voltage above the lockout floor, the BMS releases and the phone boots normally.