HBU83S MetroPCS M635 Replacement Battery 3.7V 950mAh

MetroPCS M635 / Pinnacle 2 — 3.7V Li-ion Replacement Battery (HBU83S)

This is a 3.7V, 950mAh Li-ion replacement battery for the MetroPCS M635, M636, Pinnacle 2, and related handsets. It uses OEM part numbers HBU83S and HB4A1H. Physical dimensions are 53.78 × 34.05 × 4.80mm — measure your original before ordering if you're unsure of your exact variant.

• M635 and Pinnacle 2 compatibility: These models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The BMS handshake is identical across the M635, M636, and Pinnacle 2 lineup, so one cell fits all without adapter or modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the M635 platform. The BMS accepted the cell on first insertion, reported state-of-charge correctly after one full cycle, and thermal readings stayed within normal limits throughout.
• First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the charge controller starts applying higher current. Skip this and the OS may report inaccurate percentages for the first several cycles.

Why the M635 reports wrong battery percentage after a cell swap

The M635 uses a fuel gauge IC that builds its state-of-charge model around the discharge curve of the original cell. When you install a new cell, the IC is still referencing the old curve. Until it recalibrates, the percentage display can read high or low by 10–20%. One full discharge from 100% down to automatic shutdown, followed by an uninterrupted charge to 100%, resets the coulomb counter and aligns the IC to the new cell. After that cycle, percentage accuracy normalises.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. Under modem transmission load or screen-on draw, the cell's terminal voltage drops sharply before the fuel gauge registers it. The phone shuts off because the processor loses its minimum voltage rail, even though the gauge still shows charge remaining. It happens most often in the first few cycles before the fuel gauge recalibrates. Run two full discharge-charge cycles without fast charging — if the shutdowns continue past that point, check that the replacement cell is seated fully and the connector is locked flat, then verify resting voltage reads at least 3.7V with a multimeter.