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/Electric Vehicle Battery Interface Control Module with wireless transmitter/receiver.

The A4 Hybrid/Electric Vehicle Battery Pack is assembled in two layers. The CMAs in each layer are configured in series, essentially operating like two battery packs in one assembly. The total voltage per layer is about 400V. Under normal operating conditions these two layers operate electrically in parallel with each other. If charging conditions allow, the high voltage contactors can be configured such that each layer is wired in series to facilitate 800V charging. Each layer is monitored independently by the K16A Battery Energy Control Module. The upper level is pack 1 and the lower level is pack 2.

During 800V charging only one battery pack layer supplies normal pack voltage (400V) to the high voltage components of the vehicle. After several minutes the battery pack layer connected to the vehicle will be switched so that one layer is not charged more than the other and they stay in balance. At no time is 800V supplied to the vehicle high voltage components.