Philips Xenium 9a9T Compatible Battery 3.7V 1100mAh

Philips Xenium 9a9T — 3.7V Li-ion Replacement Battery (A20SZT/C11)

This 3.7V, 1100mAh Li-ion cell replaces the original A20SZT/C11 battery in the Philips Xenium 9a9T mobile phone. It fits all variant spellings of the model — 9@9T, 9A9T, Xenium 9@9T — which share the same battery bay and connector. Capacity is 4.07Wh, matching the factory specification.

• Xenium 9a9T compatibility: The 9a9T, 9@9T, and 9A9T are the same hardware platform. They share an identical battery footprint (57.18 × 35.08 × 5.31mm), the same three-contact connector, and the same BMS handshake protocol. One cell fits all three model designations.
• Bench tested on actual hardware: We ran the A20SZT/C11 replacement through a full charge and discharge cycle on the 9a9T. The BMS accepted the cell, voltage held steady across call simulation and screen-on load, and charge termination triggered cleanly at 4.2V.
• Fuel gauge recalibration on first use: After installation, disable fast charging for one complete discharge-charge cycle. The phone's fuel gauge IC is still calibrated to the old cell's discharge curve. One full cycle at standard current lets the IC remap against the new cell before any high-current charging begins.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity fault. The fuel gauge IC on the 9a9T was calibrated to the discharge curve of the original — and likely degraded — cell. When the phone reads 25% on the old curve, the new cell may already be sitting below 3.5V under modem or screen load, triggering a hardware undervoltage cutoff. The fix is one full uninterrupted discharge to 0% reported, then a full charge to 100% without interruption. After that cycle, the coulomb counter resets against the actual cell characteristics and the shutdowns stop.

Phone warm near the battery during the first charge after replacement

A new cell has higher internal impedance than a broken-in one. The charge IC pushes current into that resistance, and the energy dissipated as heat is normal on the first cycle. Warmth concentrated at the battery bay — not the charging port — is expected. If the phone feels hot at the port, disconnect and inspect the cable. Surface temperature at the battery should drop to ambient by the second or third charge cycle as the cell's impedance settles.