Battery Management While The Engine Is Idling

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

While the engine is idling, the battery sensor measures current, voltage, and temperature values of the battery, and this data is sent to the gauge control module via the UART line. The gauge control module sends the idle speed control signal and alternator control signal to the PCM via the F-CAN A line. Then, based on those signals and the signal from the ELD, the PCM determines the idle speed that is appropriate for the current state of charge of the battery, and also controls the alternator output. Because of these functions, battery condition is maintained, and fuel economy is improved.

If the battery sensor detects any problems, a warning message is shown on the multi-information display (MID) to inform the client that the system needs attention.

Fig 1: Battery Management System Diagram - While Engine Is Idling

Courtesy of AMERICAN HONDA MOTOR CO., INC.

NOTE:

Even though the engine is not idling, the warning messages will be shown as long as the ignition switch is ON (II).
If there are any problems with the charging system or the battery, the charging system indicator comes on at the same time.
The most common causes for "BATTERY CHARGE LOW" message are:
1. Short-trip driving
2. Using vehicle electrical devices or aftermarket electrical accessories for long periods with the engine OFF and the ignition ON.
If the "BATTERY CHARGE LOW" message is displayed after fully charging the battery, disconnect the gray 2-pin connector next to the Battery Sensor for 10 seconds, then reconnect the connector and the warning will be removed from the display.
If battery replacement is required, always replace with a new battery of the same group size.