Neither Alstom’s validation processes nor fault monitoring processes were sufficient to detect the overcharging of batteries prior to the event.
The ATSB is satisfied that the safety actions taken by Alstom will reduce the risk of this safety issue.
Alstom advised the following safety actions had been taken and were applicable to the global X05 fleet:
Immediately following the occurrence, Alstom made changes to the remote monitoring system to generate an automatic alert if a battery over temperature fault was detected. Automatic alerts are sent to the engineering and maintenance personnel for actioning.
Alstom also advised that in June 2020, two new fault codes were created within the TCMS to monitor the battery temperature and charging current on the SLR fleet. The faults were designed to detect and escalate the response depending on the fault severity.
The first fault code (IOS-52-2) monitored the charging current and generated an alert if the charging current exceeded 3 A for more than 5 minutes during float charging. The driver was alerted with a message on the DDU that there is a fault with the 24 V battery charging and to complete their journey.
The second fault code (IOS-52-3) monitored two parameters and isolated the battery charger if:
The DDU displayed the fault to the driver and the LRV must return to the depot.
Monitoring of the newly introduced fault codes found that they functioned although there were some spurious fault detections which did not alert the driver. Further review of battery temperature data from LRV 053 and the X05 fleet was used to refine the fault monitoring criteria.
In October 2020 a new release of the TCMS software contained revisions to improve battery temperature monitoring. Monitoring the charging current was removed and fault code IOS 52-3 was deleted. Fault code IOS-52-2 now monitors the following criteria and generates and alert if:
If any of the above are detected, the driver is alerted with a message on the DDU that there is a fault with the 24 V battery charging and to return to the depot.
The ATSB notes that the changes to the software validation and introduction of an additional fault code within the TCMS would likely prevent recurrence.