Overview of E-Bus Maintenance

In this article, we will provide an introduction to what needs to be considered for E-Bus maintenance, and show you examples.

Maintenance Practices:

• promoting energy-efficient driving behaviors
• understanding and preparing for bus and fueling
• infrastructure maintenance activities, including spare parts
• monitoring battery state of health
• inventories and lead times.

Maintenance responsibilities should be clarified as part of the procurement process. During the procurement process, it is essential to establish and define maintenance responsibilities. Clarifying maintenance responsibilities upfront helps ensure that both the buyer and the supplier know their respective maintenance roles and obligations.

The level of maintenance support required from the supplier(s) will vary from customer to customer. For example, operators with technology experience may decide to carry out much of the bus maintenance themselves and only require a spare parts package from the bus supplier.

On the other hand, an operator new to fuel cell buses may prefer to stay out of maintenance and seek a comprehensive support package where the bus OEM (or its suppliers) provides personnel to carry out most of the bus maintenance tasks.

In any case, it is vital to ensure that sufficient spare parts (both consumable and strategic) are available. In (or near) the workshop/depot, qualified technicians are always available for scheduled and unscheduled maintenance.

In addition, maintenance of fuel cell buses requires specialized tools such as hydrogen sensors (sniffers), software to monitor vehicle systems and diagnose problems, etc. (Dolman & Gallmetzer, 2019)

E-Bus Maintenance

Click to expand. E-Bus Charging. Medimorec (2014)

The maintenance of the bus includes components that are considered to require electrical maintenance, for example:

• Li-ion battery packs
• Battery Management System (BMS)
• power distribution unit
• traction motor drive
• wire harness systems
• converter & onboard charger
• vehicle control unit.

The only component that is considered to be subject to mechanical maintenance is the Mechanical Transmission System.

Spare Parts Inventory

Many companies rely on their stock of parts, spares, and consumables to ensure timely repairs and maintenance of buses. However, several considerations need to be taken into account:

• the availability of spare parts is a common problem in the transport industry
• it is necessary to request the bus and coach OEMs and the refueling infrastructure OEMs to provide a list of critical and recommended spare parts for field use
• taking stock of spare parts can help expedite the repair process
• request pricing and standard lead times from OEMs to determine expectations for E-Bus downtime

Preventive Maintenance

For this type of maintenance, it is essential to ask bus and infrastructure manufacturers to provide a list of activities, time intervals, skills, and parts required to perform each task for efficient maintenance. Some activities may require the expertise of licensed electricians or OEM technicians.

Here are some activities to perform during preventive maintenance:

• Lubricating the mechanical transmission parts:
  • gearbox
  • differential
• Changing coolant for liquid-cooled electric drive.
• Checking electrical systems at critical points in an electric powertrain:
  • battery terminals
  • Power Distribution Unit (PDU) input/output
  • 12V/24V power line converter output
  • continuity and electrical insulation check for the entire vehicle to ensure the health of all electrical the integrity of all electrical connections and prevent chassis short circuits or other critical leaks
• Checking the signals at key points, including:
  • all subsystems communicate via Controller Area Network (CAN)
  • motor feedback signal
  • Battery Management System feedback
  • signal check between the driver’s input (throttle) and the vehicle control unit
• Powertrain fault history is checked in the vehicle’s local log files:
  • this is a crucial implementation where a local memory on the vehicle control unit should store all major powertrain faults and malfunctions with time history

Course Mascot. PEM Motion (2023)

Charging Infrastructure Maintenance

OEMs provide maintenance manuals outlining preventive maintenance activities, the time and skill required to perform them, and fault codes and troubleshooting.

• Depot Charging Stations:
  • often modular, requiring minimal maintenance.
• Fast charging stations:
  • Require ongoing preventive maintenance as they typically have cooling systems, filters, and other components.

SOH = State of Health

This parameter is essential because it is directly related to battery performance. This provides beneficial data for optimizing the Battery Management System (BMS).

A battery’s State of Health (SoH) describes the difference between a used battery under test and a fresh battery considering the battery cell aging.

It is defined as the ratio of the battery’s maximum charge to its rated capacity. It is expressed as a percentage, as shown below.

SoH(%)=100 Qmax/Cr

“Qmax” = The maximum charge available of the battery “Cr” = The rated capacity

SOH Indicates: – performance of the battery – useful lifetime of the battery consumed.

Conclusion

This overview highlights several factors to consider for the maintenance of E-Buses, including the customer type and their access to original equipment manufacturer (OEM) spare parts, as well as maintaining an inventory of essential components for efficient maintenance.

Implementing good maintenance practices, such as preventive maintenance and monitoring battery performance, can significantly enhance the sustainability and safety of E-Buses

Next, we will explore and gain an understanding of the contrasting maintenance requirements between E-Buses and diesel buses.

References

• C40 CITIES FINANCE FACILITY. (2021) Understanding zero-emission bus maintenance. Retrieved from: Link
• Dolman, M., & Gallmetzer, M. (2019) Operators’ guide to fuel cell bus deployment: JIVE 2 Project. Retrieved from: Link