BoostMobile N9515 Replacement Battery 3.7V 1800mAh

BoostMobile N9515 / WARP SYNC — 3.7V Li-ion Replacement Battery

This 3.7V, 1800mAh Li-ion cell replaces the original battery in the BoostMobile N9515 and WARP SYNC smartphones. It fits phones where the stock cell has degraded through repeated charge cycles and can no longer hold a usable charge. Dimensions are 72.74 × 53.41 × 4.67mm — verify these against your current cell before installing.

• N9515 and WARP SYNC compatibility: Both models share the same battery bay dimensions, connector pinout, and charge IC handshake, so a single cell covers either unit without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge under screen-on and modem-active loads. The BMS held the charge rail stable across the full discharge curve without false cutoff events.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins — skipping this step causes erratic percentage readings for several cycles.

Sudden shutdown at 20–30% on a replacement cell

The N9515's fuel gauge IC stores a discharge curve calibrated to the original cell's internal resistance profile. A new cell has a different impedance, so the IC misreads the actual state of charge — it reports 25% remaining while the cell voltage has already dropped below the modem's minimum operating threshold. Under the combined load of an active radio and display, the phone shuts down even though the percentage counter shows charge remaining. Run two full discharge-charge cycles without fast charging to force the coulomb counter to recalibrate against the new cell, after which the reported percentage will track the real voltage accurately.

Device will not power on after the battery sat in storage

Li-ion cells self-discharge in storage. If this battery shipped or sat unused long enough for the cell voltage to drop below approximately 2.5V, the BMS enters lockout mode and blocks all current flow to protect the cell from permanent damage. The phone shows no response — no boot logo, no charging indicator — even when plugged in. Connect the phone to a wall adapter rated at 5V/1A or higher and leave it for 20–30 minutes without pressing the power button. The charge IC will trickle current into the cell until voltage climbs back above the BMS wake threshold, at which point the charging indicator will appear and normal operation resumes.