BoostMobile MAX Replacement Battery 3.8V 3200mAh Li-Polymer

BoostMobile MAX / N9520 — 3.8V Li-Polymer Replacement Battery

This 3.8V, 3200mAh Li-Polymer battery replaces the original cell in the BoostMobile MAX and N9520 smartphones. It matches OEM voltage and capacity specifications. Install it when the original cell no longer holds a usable charge through a normal day of use.

• MAX and N9520 compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. This cell fits either device without modification — the same 3.8V nominal rail and 95.58 × 57.15 × 4.16 mm footprint cover both.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the MAX platform. The BMS accepted the cell without fault flags, charge termination triggered correctly at full capacity, and protection cutoffs fired within spec on over-discharge simulation.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging pushes current into an uncalibrated cell.

Sudden shutdown at 20–30% on the BoostMobile MAX after a cell swap

A new cell has a different discharge curve than the aged original. The fuel gauge IC on the MAX is still referencing the old curve, so when the new cell's voltage drops quickly under modem or screen load, the IC sees a voltage cliff it wasn't expecting. The phone interprets that as a critically low state and shuts down — even though the reported percentage still shows 20–30%. One full discharge-to-shutdown followed by a complete charge cycle forces the coulomb counter to re-anchor to the new cell's actual capacity floor.

OS reporting wrong battery percentage after replacement

The Android fuel gauge IC on the N9520 and MAX stores learned capacity data from the previous cell. After swapping cells, that stored profile no longer matches the new cell's impedance and capacity. Percentage readings can jump erratically or plateau well above or below the true charge state. Run one full charge from 0% to 100% without interruption — this clears the stored learned data and lets the IC recalibrate against the new cell's actual voltage-to-capacity curve.