Circuit/System Description

The high voltage A4 Hybrid/Electric Vehicle Battery Pack consists of lithium-ion cells. Several cells are welded together in series or parallel and called a cell group. The cell groups are electrically joined in series to form the Cell Module Assembly (CMA) also known as a high voltage section battery. Based upon option content, the battery pack may contain up to 24 CMAs. Each CMA is identical, although uniquely serialized, and contains a non-serviceable K112 Hybrid/EV Battery Interface Control Module with wireless transmitter/receiver.

Each K112 Hybrid/Electric Vehicle Battery Interface Control Module monitors the temperature, current and voltage of its respective cell groups. Each K112 Hybrid/Electric Vehicle Battery Interface Control Module is also responsible for balancing the voltage of each cell group via internal resistance circuits. Each K112 Hybrid/Electric Vehicle Battery Interface Control Module communicates wireless with the K291 Hybrid Electric Vehicle Battery Pack Communication Module which is also located within the battery pack. The K291 Hybrid/ Electric Vehicle Battery Pack Communication Module in turn communicates with the vehicle mounted K16A Battery Energy Control Module (BECM) via wired communication circuits. The K16A BECM is the host controller for all battery diagnostics and system status.

In order for the system to communicate wirelessly with each cell module assembly (CMA), the unique CMA MAC address is stored in an access control list (ACL). The K291 Hybrid Electric Vehicle Battery Pack Communication Module is considered the master of this list, and a copy of the list resides within the K16A Battery Energy Control Module. In normal operation the K16A Battery Energy Control Module list is copied from the K291 Hybrid Electric Vehicle Battery Pack Communication Module the first time they communicate or whenever the K16 Battery Energy Control Module list is empty. If however the K291 Hybrid Electric Vehicle Battery Pack Communication Module list is empty it will learn the CMA MAC address list from the K16A Battery Energy Control Module. If both module lists are empty, the CMA MAC addresses must be manually restored using a scan tool.

The K16A Battery Energy Control Module compares the software expected number of CMA MAC addresses to the quantity stored in the access control list, and will set a DTC when too few or too many CMA MAC addresses are present.