Audi 8W7907468D Emergency Supply Compatible Battery 3.2V 1500mAh

Audi 8W7907468D Emergency Supply — 3.2V LiFePO4 Replacement Battery (4K0915989A)

This 3.2V, 1500mAh LiFePO4 cell replaces the backup battery inside the Audi 8W7907468D emergency power supply unit. It fits the A4, A5, and related models that use OEM part 4K0915989A or cross-references 4M0907486, 9A7915989A, and A2C01600000. When the main vehicle battery fails or disconnects, this cell keeps emergency lighting and eCall/SOS systems powered.

• A4 and A5 platform compatibility: These models share a common emergency supply architecture with the same connector pinout, 3.2V LiFePO4 chemistry requirement, and BMS handshake protocol — swapping between variants listed does not require any wiring change.
• Bench tested on actual hardware: We cycled this cell through the 8W7907468D unit's charge management circuit. The BMS accepted the cell on the first cycle, held charge termination at 3.65V, and engaged the low-voltage protection cutoff at 2.5V without fault codes triggering.
• Post-install charge cycle requirement: After fitting, leave the vehicle's ignition in accessory mode for a minimum of two hours before parking long-term — the 8W7907468D management module will not log the battery as "ready" until it completes one supervised charge pass from the vehicle's 12V rail.

Why the 8W7907468D shows a battery fault immediately after a new cell is fitted

The 8W7907468D emergency supply module runs a voltage-presence check within seconds of detecting a new cell. If the replacement cell ships at a storage charge below roughly 3.0V, the module logs a fault before the charge circuit can bring it up. This is not a compatibility failure — it is the module's safety threshold rejecting an uncharged cell. Connect the vehicle to a power supply or run the engine for 30 minutes and the fault will clear once the cell crosses the module's acceptance threshold of approximately 3.1V.

Emergency supply self-test failure after battery replacement

The 8W7907468D runs a periodic self-test that includes a brief discharge-under-load check to validate the battery can sustain emergency draw. A freshly installed cell that has not completed a full charge cycle will fail this test because the module cannot confirm usable capacity. The fix is straightforward: allow a full supervised charge cycle — cell voltage must reach 3.65V — before the self-test runs. If the test failure persists after a full charge, check that the cell's dimensions match the 68.00 × 37.20 × 18.70mm spec, as poor contact with the module terminals causes the same symptom.