An OBD Compliant 12V Main Battery and DEC-ECU. Wait, what??

"This presentation comes from direct experiences developing an OBDII Compliance solution for a 12V Main, or starter battery. This is not your typical OBD-relevant component, inasmuch as �1968.2 (e)(17.5) allows one to, ��disable monitoring systems that can be affected by vehicle battery or system voltage levels.� OEMs interpret these requirements such that the 12V Main Battery, alternator, power distribution, etc. are all exempt from OBD Monitoring. However, it is possible to bring such systems into relevance based on how they are used by the emissions control or OBDII System of the vehicle. Many OEMs have adopted the use of Intelligent Battery Sensors, and these sensors provide state-of-charge, voltage, current and temperature information to the vehicle systems. The powertrain controls can then utilize this data to enable the efficient use of the alternator for charging, such that energy savings can be realized by varying the charge current to the 12V battery. The same information can also be used to enable/disable OBDII Diagnostics, because it is a direct indication of System Voltage. The intelligent Battery Sensor is typically classified as a Smart Device, enabling the use of the data it provides for these purposes in an OBDII-Compliant manner. 12V Lithium-Ion batteries have been utilized in vehicle applications where the vehicle developer wants the performance of a Lead-Acid battery in a smaller, lighter package. Lithium-Ion batteries come with a battery management system (BMS) that measures voltage, current and temperature to communicate charge and discharge power limits to the vehicle. This BMS replaces the intelligent battery sensor, and the number of inputs and outputs disqualify the BMS as a Smart Device, but the data provided by the BMS is still used to enable/disable OBDII Diagnostics. Therefore, the BMS becomes a DEC-ECU and is a key component to System Voltage."