AB1200CWMT Philips E135x Replacement Battery 3.7V 1100mAh

Philips Xenium E135x — 3.7V Li-ion Replacement Battery (AB1200CWMT)

This is a 3.7V Li-ion cell rated at 1100mAh (4.07Wh), sourced to match the OEM specification for the Philips E135x and Xenium E135x feature phones. It replaces part number AB1200CWMT directly. The E135x is a basic GSM phone, and this cell restores full call and messaging function when the original battery no longer holds adequate charge.

• E135x and Xenium E135x compatibility: Both variants share the same battery bay geometry, contact spacing, and 3.7V nominal voltage rail. No BMS handshake is required on this platform — the charge IC reads cell voltage directly, so cell swaps are straightforward.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the E135x platform. The charge IC accepted the new cell without error flags, and the protection circuit triggered correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge to automatic shutdown, then charge uninterrupted to 100% before normal use. The E135x fuel gauge tracks coulomb count against the old cell's curve — one full cycle rewrites that baseline against the new cell, preventing erratic percentage readings.

Why the E135x reports wrong battery percentage after a cell swap

The E135x fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, the IC applies that old curve to the new cell's actual voltage readings, producing mismatched percentage figures. The mismatch is worst in the middle of the charge range and corrects itself after one full discharge-to-shutdown and uninterrupted recharge cycle. After that single cycle, the gauge recalculates against the new cell's actual voltage-to-capacity relationship.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — typically during a voice call when the GSM radio draws a burst of current — before the fuel gauge registers low battery. A freshly installed cell with an uncalibrated fuel gauge makes this worse, because the IC underestimates how close to the cutoff voltage the cell actually is. The protection circuit then hits its 3.0V cutoff and shuts the phone down while the display still shows 20–30%. One full calibration cycle resolves the gauge mismatch; if shutdowns continue after that, check resting voltage with a meter — a healthy cell at rest should read above 3.6V.