System Operation - 12 Volt Dual Battery System - ADAS Equipped

WARNING: This page is about a different variant/trim than selected.

The dual battery Engine Stop/Start (ESS) system consists of four main components that are connected to and operate the starting, charging and vehicle electrical systems. The following four components make up the dual battery system:

Main Battery
Auxiliary Battery
Dual Battery System Module (DBSM)
Dual Battery System Fuse

NOTE:

The DBSM replaces the Power Control Relay (PCR) on vehicles equipped with the ADAS system. The DBSM separates the system into two sides, the main battery side and auxiliary battery side.

The main battery is the larger battery that is directly connected to the starter when the batteries are isolated.
The auxiliary battery is the smaller battery that is directly connected to the alternator and Power Distribution Center (PDC) powering the modules and accessories when the batteries are isolated.

There is an Intelligent Battery Sensor (IBS) connected in series on both battery negative cables which provides information about the batteries to the Body Control Module (BCM) over a Local Interface Network (LIN) bus. The IBS monitors the current flow going out of the batteries, and current flowing into the batteries during charging to make these calculations. Some of the information stored and provided by the IBS are:

Battery voltage
Battery temperature
Battery State of Charge (SOC) - The battery SOC is the percentage of battery charge based on measured voltage, charge and discharge rates.
Battery State of Function (SOF) - The SOF is the calculated voltage that the battery will drop to when the starter is engaged to crank the engine.
Battery State of Health (SOH) - The SOH is the measurement of current battery capacity along with depreciation in battery health.

The BCM broadcasts the IBS and IBS 2 data over the CAN bus. The Powertrain Control Module (PCM) will use the battery SOC to determine charge rates as well as when to allow features such as the Engine Stop/Start (ESS) system to function. The BCM uses the battery information received from IBS and IBS 2 to make decisions on load shedding when battery SOC is determined to be low.

In a normally functioning system, the two batteries (main and auxiliary) of the system are always connected through the Dual Battery System Module (DBSM) except for the brief periods during cranking events. Both batteries are connected to the entire electrical system during this mode. This allows charging of the main battery through its connection to the auxiliary battery side, and the main battery to be connected to the Power Distribution Center (PDC) and assist the auxiliary battery in operating the modules and accessories.