MetroPCS Ascend II HB5K1H Replacement Battery 3.7V 1200mAh

MetroPCS Ascend II — 3.7V Li-ion Replacement Battery (HB5K1H)

This is a 3.7V, 1200mAh Li-ion cell for the MetroPCS Ascend II smartphone. It replaces OEM part number HB5K1H and restores power to calls, messaging, and Android applications. Capacity matches the original factory specification at 4.44Wh.

• Ascend II fit: The Ascend II uses a removable 49.50 × 44.20 × 4.50mm cell with a low-current BMS suited to its basic Android load profile. This replacement matches that footprint and connector orientation exactly — no case modification needed.
• Bench tested on actual hardware: We cycled this cell through charge and load on the Ascend II platform. The BMS accepted charge handshake without error, held voltage above 3.5V under combined modem and screen load, and shut down cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge to automatic shutdown followed by a full uninterrupted charge. This lets the Ascend II's fuel gauge IC map the new cell's discharge curve before it starts reporting percentages to the OS.

Sudden shutdown at 20–30% on the Ascend II after a cell swap

The Ascend II's fuel gauge IC stores a discharge curve calibrated to the old, degraded cell. When a fresh cell goes in, the IC underestimates remaining capacity because the new cell holds voltage higher for longer before dropping sharply. At the voltage cliff — typically around 3.5V under modem load — the phone cuts power before the percentage readout reaches zero. One full discharge-to-shutdown cycle followed by a complete charge resets the coulomb counter and corrects the reported percentage against the actual cell curve.

Ascend II not powering on after the replacement cell sat in storage

Li-ion cells self-discharge in storage. If this cell dropped below approximately 2.5V per cell during shipping or warehouse time, the BMS enters lockout to prevent damage and the phone will not respond to the power button. Connect the phone to a wall charger — not a PC USB port — and leave it for 15–20 minutes without pressing anything. The charge IC will trickle current into the cell until voltage rises above the BMS recovery threshold, typically around 2.9V, at which point normal charging resumes and the phone will power on.