vehicle. This level should be required to operate any electric school bus. The second level of training (HV2) goes a few steps
beyond that, with a high emphasis on safety. This level is for technicians servicing low-voltage systems on the vehicle, isolating the voltage from the high-voltage systems and checking the isolation from the supply. It trains on securing the high-voltage system against being activated, re-starting the high-voltage system, performing inspection of the de-energized, high-volt- age systems and components, and assessing the risk of high-voltage vehicles that were involved in an accident. Knowledge of personal protection equipment and how to work around the high-voltage systems is included. The final and most advanced level (HV3) focuses on
high voltage and de-energizing the BEV (battery electric vehicle). This is specifically for those who are working closely with high-voltage systems inside of the bus, cen- tered around decommissioning those systems. Not all
electric bus maintenance requires decommission, which is why this level is not required for all. Recently, the National Institute of Automotive Service
Excellence (ASE) has developed Electrified Propulsion Vehicles (xEV) High-Voltage Electrical Safety Standards. This is in addition to the S-1 to S-7 certification programs already available to mechanics to become ASE Master Certified School Bus Technicians. The ASE process brought together volunteers rep-
resenting varied viewpoints and interests to achieve consensus on electrified propulsion vehicle safety issues. The ASE Electrified Propulsion Vehicles (xEV) High-Voltage Electrical Safety Standards will serve as an excellent guide, sharing existing industry standards, concepts, and practices followed by individuals work- ing in the automotive, truck and commercial electrical industry. Anyone adding electric school buses to their fleet should consider the ASE xEV certification process for their technicians. ●
Robert Pudlewski is STN’s technical editor and a member of the National School Transportation Association Hall of Fame in recognition of his 40-plus year career as a school bus maintenance, technology and procurement expert.
Risk Management Considerations for Electric Buses, Hazards & Recommendations
1. Hazard – While some electric school bus (ESB) manufacturers have recently switched to more stable lithium-iron phosphate batteries, many vehicles already on the road are powered by lithium-ion batteries. There have been reported risks associated with the possibility of lithium-ion batteries reaching thermal runaway due to failure of internal components. These fires could be very intense and flare rapidly. If a fire were to occur due to a thermal runaway event originating from a faulty battery cell, maintenance issues, or other causes (accident/collision), specialized fire suppression may be needed. Recommendation – Work with the ESB manufacturer, electrical contractor, local fire department, local fire marshal, and local police to explore all potential hazards, suppression methods and response times. Form an emergency response plan that adequately addresses the known hazards.
2. Hazard - Battery discharge, proper maintenance of batteries and related components, and proper disposal of batteries. Recommendation - Maintenance technicians need to be fully trained on battery discharge procedures, and the use of PPE equipment, to alleviate the opportunity for thermal runway and/or workplace hazards due to electrical shock. OEM providers of the batteries should be contacted to identify and address safety equipment, preventative maintenance, storage, and disposal of batteries.
3. Hazard - Inadequate training for ESB drivers. Drivers should be trained to understand the different types of hazards associated with ESB versus the traditional diesel/gas powered buses. Recommendation – Ensure ESB drivers have safety training including recognizing early warning signs of a thermal runaway and evacuation response to such an event. Yearly training for drivers should take place in all aspects of the above-described events and related hazards response.
4. Hazard – ESB Charging Station Recommendation – Avoid attaching the charging station near regular bus fleet and/or heavy foot traffic areas. Large electrical charging cables can pose trip and fall hazard(s). Ensure the charging station is in an area with proper storm water drainage.
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