Philips Xenium S598 Replacement Battery AB4000CWMT 3.85V

Philips Xenium S598 / CTS598 / X598 — 3.85V Li-Polymer Replacement Battery (AB4000CWMT)

This is a 3.85V, 3900mAh lithium-polymer battery for the Philips Xenium S598, CTS598, and X598 smartphones. It replaces OEM part AB4000CWMT. If your phone shuts down unexpectedly, charges slowly, or drains faster than it used to, the original cell is likely past its service life.

• S598, CTS598, and X598 compatibility: All three model variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The AB4000CWMT part number covers the full range — no adapter or modification needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S598 platform. The BMS accepted the cell without error, the charge IC stepped through its CC/CV stages correctly, and fuel gauge registration completed within the first full cycle.
• 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 the new cell's discharge curve before high-current charging pushes load into an uncalibrated state. Skip this step and the OS percentage readout may drift for several cycles.

Sudden shutdown at 20–30% on the Xenium S598

This is a voltage cliff failure, not a capacity problem. When the modem transmits or the screen peaks brightness, current draw spikes sharply. An aged cell cannot hold its voltage under that load — it drops below the BMS cutoff threshold even though the fuel gauge still reads 20–30%. A fresh 3900mAh cell with lower internal resistance sustains voltage through those spikes. After fitting the replacement, run one full discharge to 0% and charge to 100% so the coulomb counter resets its floor and ceiling against the new cell's actual voltage curve.

USB fast charge not working after fitting the replacement cell

The Xenium S598's charge IC performs a BMS handshake before it steps up to fast-charge current. On the first cycle with a new cell, the IC sometimes stays in trickle or standard charge mode because it hasn't yet confirmed the cell's temperature and impedance profile. This is normal behaviour — not a fault with the battery or the charger. Unplug, wait 30 seconds, and reconnect. If fast charging still doesn't engage after a full standard-rate charge cycle, check that the charge port is clean and the cable supports the required current rating.