About this replacement
Asus P552w — 3.7V Li-ion Replacement Battery (SBP-18)
This is a 3.7V, 2200mAh Li-ion replacement battery for the Asus P552w smartphone. It fits directly in place of the original SBP-18 cell. The P552w is a Windows Phone-based device, and this battery restores full power to calling, messaging, and app functions.
- P552w platform fit: The P552w uses a specific connector and BMS handshake tied to the SBP-18 form factor. This cell matches the 52.18 × 42.03 × 10.15mm footprint and the 3.7V nominal voltage rail the device's charge IC expects. Swapping an incorrect cell voltage here causes the charge controller to reject the battery entirely.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the P552w platform. The BMS accepted the charge handshake without fault flags, and the fuel gauge IC tracked state-of-charge through the full curve without erratic readings mid-cycle.
- First-cycle calibration on the P552w: After installation, disable fast charging and run one full discharge-to-charge cycle before enabling high-current charging. The fuel gauge IC on this device calibrates its coulomb counter against the new cell's discharge curve on that first cycle. Skipping this step leaves the percentage readout misaligned by up to 15% for days.
Sudden shutdown at 20–30% on the P552w after a cell swap
This happens because the fuel gauge IC is still using the discharge curve it mapped to the old, degraded cell. When the new cell hits a voltage point that the old curve read as 20–30%, the IC can't predict the real voltage drop under modem or screen load. The phone shuts down not because the cell is empty, but because the IC flagged an unexpected voltage cliff. One full discharge cycle — drain to auto-off, then charge uninterrupted to 100% — forces the coulomb counter to remap against the new cell. After that cycle, shutdowns at falsely low percentages stop.
P552w not powering on after the replacement battery sat in storage
Li-ion cells in storage self-discharge over time. If the cell drops below 2.5V, the BMS enters a lockout state to prevent damage from deep discharge. The P552w won't power on and may show no charging indicator at all when connected to USB. Connect the device to a wall charger — not a PC port — and leave it for 20–30 minutes without attempting to power on. The charge IC will trickle-charge the cell back above the BMS recovery threshold, typically around 2.9V, at which point the device will boot normally.