About this replacement
Philips Xenium S318 / CTS318 — 3.8V Li-Polymer Replacement Battery (AB2500AWMT)
This is a 3.8V, 2300mAh (8.74Wh) Li-Polymer cell built to the AB2500AWMT specification. It fits the Philips Xenium S318 and CTS318 smartphones. Voltage, connector footprint, and BMS handshake all match the OEM part.
- S318 and CTS318 compatibility: Both models run the same battery bay geometry, 3.8V nominal rail, and AB2500AWMT connector pin-out. The BMS on each device accepts the same charge termination signal, so one cell covers both variants without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the S318 platform. The BMS accepted the charge handshake cleanly on the first cycle, voltage held steady under combined screen and modem load, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-to-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging pushes current into an uncalibrated state.
Sudden shutdown at 20–30% on the replacement cell
This happens when the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell has a different voltage-versus-capacity profile, so the IC misreads remaining charge and the phone hits the hardware low-voltage cutoff before the percentage display reaches zero. Under modem or display load, voltage drops sharply at the knee of the discharge curve — faster than the IC predicts. One full discharge-charge cycle at standard current forces the coulomb counter to resync against the new curve. After that cycle, shutdowns at 20–30% typically stop.
Device not powering on after the battery sat in storage
Li-Polymer cells self-discharge during storage. If the cell voltage drops below approximately 2.5V, the BMS enters lockout and blocks normal charge current to prevent thermal runaway on a deeply discharged cell. The phone will not respond to a charger or power button in this state. Connect a known-good USB charger and leave it for 20–30 minutes — most chargers deliver a trickle pre-charge current that nudges the cell above the BMS re-enable threshold. Once the cell recovers to around 3.0V, the BMS releases and normal charging resumes.