Asus Pegasus X005 Replacement Battery 3.8V 4000mAh

Asus Pegasus X005 — 3.8V Li-Polymer Replacement Battery (PS-486490)

This is a 3.8V, 4000mAh lithium-polymer battery for the Asus Pegasus X005 smartphone. It replaces OEM part PS-486490, the internal cell that powers this device. Install it when the original battery no longer holds charge, swells, or shuts the phone down unexpectedly.

• Pegasus X005 fit: The PS-486490 footprint — 89.20 x 62.50 x 4.50mm — matches the Pegasus X005 battery bay exactly. The connector pinout and BMS handshake align with this model's charge IC, so the phone reads cell state correctly from the first boot.
• Bench tested on actual hardware: We cycled this cell through charge and discharge under load conditions that replicate modem, display, and GPS draw. The BMS held voltage above the cutoff threshold and reported state-of-charge to the fuel gauge IC without triggering a false low-battery shutdown.
• First cycle after installation: Disable fast charging for the first complete discharge-charge cycle. This gives the fuel gauge IC time to recalibrate against the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated cell.

Why the Pegasus X005 shuts down suddenly at 20–30% after a cell swap

The fuel gauge IC on the Pegasus X005 stores a discharge curve calibrated to the old cell. A new cell has a different internal resistance profile, so the IC misjudges remaining capacity. When the phone hits a load spike — modem handshake, screen brightness burst — the voltage drops below the shutdown threshold faster than the IC predicts. One full discharge-charge cycle without fast charging lets the coulomb counter recalculate the actual curve of the new cell and eliminates premature cutoffs.

USB fast charge not activating on the replacement cell's first cycle

On the first charge after installation, the charge IC may default to standard 5V/1A input instead of engaging the fast charge protocol. This happens because the BMS on the new cell starts with a conservative pre-charge phase until cell voltage clears 3.0V. Once the cell climbs past that threshold, the charge IC re-negotiates the fast charge handshake automatically. If fast charging still does not activate after the first full cycle, check that the cable and adapter support the correct protocol — the Pegasus X005 uses Qualcomm Quick Charge.