Battery Monitoring System

NOTE: When any vehicle module is being programmed, connect an external battery charger to make sure that the module programming is completed without interruption due to the load shedding feature becoming active. The external battery charger must maintain a system voltage above 13 volts. This may require a charger setting higher than the lowest charge setting. The external battery charger negative connection must be made to an engine or vehicle chassis ground and not the negative battery terminal. If the connection is to the negative battery terminal, load shedding may begin and module programming may be corrupted. After charging has begun, start the engine to clear any load shed states and then turn the engine off and proceed with programming.

This vehicle is equipped with a Battery Monitoring System which manages battery charging by the generator and monitors the battery state of charge. The Battery Monitoring System also utilizes a load shed strategy to help control discharge of the battery and prevent, when possible, an excessively low battery state of charge. The BCM monitors the battery state of charge using the battery monitoring sensor attached to the negative battery terminal and cable assembly.

To maintain correct operation of the load shed system, any electrical devices or equipment must be grounded to the chassis ground and not the negative battery terminal. A connection to the negative battery terminal causes an inaccurate measurement of the battery state of charge and incorrect load shed system operation due to the current being used bypassing the battery monitoring sensor.

The battery monitoring sensor has to be recalibrated at regular intervals. This occurs during a rest period or when the battery closed-circuit current is less than 100mA. The rest period must last for at least 3 hours. The timeframe in which a recalibration must take place is 7 days. If the system has been unable to carry out a recalibration within this time then it is impossible to confirm the exact state of charge of the battery. Any devices left attached to the power socket that draw in excess of 100mA (or less depending on other battery loads) will prevent a battery monitoring sensor recalibration.

When the ignition is in ACC or ON mode and the BCM determines the battery voltage or the battery state of charge has dropped below set levels, a low battery warning message is displayed in the message center as described below. Should the battery voltage or the battery state of charge continue to drop, the audio system is powered down to save the remaining battery charge. This load shed state clears once the vehicle has been started and battery state of charge is allowed to recover.

When the ignition is in the ON mode and if load shed occurs, the message center can display the corresponding message to notify the driver that battery protection actions are active. The audio system shuts down after the message center displays the warning.

If a fault occurs with the battery monitoring sensor or circuit(s), the only engine off load shed strategy that is active is a 45 minute timer. After 45 minutes have elapsed, the audio system turns off. To clear the load shed state, restart the engine.

If the vehicle battery is replaced, carry out the Battery Monitoring System Reset using the scan tool. If the Battery Monitoring System Reset is not carried out, measurement data collected for the old battery will not be deleted and future state of charge measurements will be inaccurate. For example, if an old battery has a state of charge of 60% and the new battery has a state of charge of 90%, the BCM will recognize battery state of charge being 30% lower than it actually is. With the battery state of charge being perceived lower than it actually is causes shedding of loads earlier than is necessary. This also impacts the smart regenerative charge system by causing the battery to be maintained at a higher state of charge than perceived by the BCM, reducing fuel economy benefits.

If the vehicle has been jump started, test the battery condition.

Refer to: BATTERY .

For charging the vehicle battery,

Refer to: BATTERY .