Battery Monitoring System (BMS)

WARNING: This page is about a different car, the 2020 Jaguar XE and 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

When the ignition is switched off, the BMS control module records the battery state of charge and begins to monitor the battery condition.

If the battery state of charge falls by 7% from the critical start point, the BMS control module will start to monitor the battery for 5 minutes and sends a 'Warning' message on the LIN bus to the BCM/GWM assembly. If the battery charge has continued to fall below 50% due to the high quiescent drain current after the 5 minute monitoring period, the BMS control module will determine that the control modules are still 'awake'. The BMS control module sends a 'Shutdown' message on the LIN bus to the BCM/GWM assembly. The BCM/GWM assembly then transmits a 'Shutdown' message on both MS and HS CAN buses to all control modules, requesting them to shutdown.

The BMS control module will monitor the battery state of charge for a further 15 minutes and determine if the battery state of charge is still dropping due to the quiescent drain current. The BMS control module sends a 'Power Disconnect' signal to the BCM/GWM assembly on the LIN bus. The BCM/GWM assembly then sends a signal to the QCCM via the LIN bus to open its internal relays. When the QCCM relays are open, the power supply from the battery to non-critical control modules is removed. The non-critical control modules are any modules associated with the infotainment system and also the climate control system.

The use of the LIN bus communication ensures that no other control modules are 'woken' during this process. If CAN bus communication was used, all modules on the CAN bus would be woken by the message.