SBP-06 Asus P526 Replacement Battery 3.7V 2400mAh

Asus P526 — 3.7V Li-ion Replacement Battery (SBP-06)

This is a 3.7V, 2400mAh Li-ion replacement battery for the Asus P526 smartphone. It replaces OEM part SBP-06 when the original cell can no longer hold usable charge. The P526 is a mid-2000s Windows Mobile handset, and finding a working original cell is increasingly difficult.

• P526 platform fit: The P526 uses a single-cell Li-ion pack at 3.7V nominal with a direct contact connector on the battery door frame. This replacement matches that contact layout and communicates correctly with the phone's charge management circuit.
• Bench tested on actual hardware: We cycled this cell through a full charge and two discharge passes on a P526 unit. The charge IC accepted the cell on the first connection, reached 4.2V at termination, and the BMS reported no fault flags throughout.
• Fuel gauge recalibration on first install: On first use, disable any sync or background data activity and run one complete discharge down to auto-shutoff, then charge to full without interruption. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before the OS reads from it.

Why the P526 reports wrong battery percentage after a cell swap

The P526 uses a fuel gauge IC that builds its capacity model from previous charge and discharge cycles. When you install a new cell, that stored model no longer matches the new cell's actual voltage-to-capacity curve. The IC reads voltage and maps it to a percentage using the old curve, so it can be off by 15–25% in either direction. One complete uninterrupted discharge-charge cycle resets the coulomb counter and lets the IC relearn the curve against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff problem, not a capacity problem. Under load from the radio modem or screen backlight, the cell voltage drops faster than the fuel gauge expects, hitting the protection cutoff threshold while the OS still shows 20–30% remaining. It happens most often when the fuel gauge IC has not yet recalibrated to the new cell. Run the recalibration cycle described above — after one full cycle, the reported percentage and the actual cutoff voltage will align more closely, and the shutdowns stop.