Hybrid & Electric Vehicle Corner
by: Curt Ward
Professor at Joliet Junior College
Teaching High Voltage Battery Systems
As I write this article, the spring semester is complete, and I am looking forward to reconnecting with my fellow instructors during the summer instructor conference season. My students will tell you that high voltage batteries are the part of the EV curriculum they enjoy the most. I will tell you that high voltage battery diagnostics and repair are some of the most difficult technologies to teach in an EV program. This is in part because the battery designs vary widely across automakers. The packs differ by chemistry, voltage range, module layout, cooling strategy, connector type, access point and service requirements. Including this technology in the curriculum can help the students identify issues involving capacity loss, internal resistance, imbalance, leakage, stored energy levels or another condition that affects battery performance and safety. In this article, I will share some of the high voltage battery experiences our students have completed inside and outside the lab.
The first battery is from a Nissan Leaf. First and second-generation Nissan Leaf batteries do not have an external cooling system. They rely entirely on heat transfer through the case. This makes this vehicle ideal for battery removal and installation lab activities (See Figure 1 – Nissan Leaf Battery). All that is needed is a lift with adequate clearance and a battery lift table with sufficient capacity. After disconnecting the high voltage and low voltage connections, it is simply a matter of removing the attaching bolts and lowering the battery. If the vehicle is a first generation Leaf the battery case is sealed with a reusable gasket. This makes it an ideal battery to open to see the internal components. Later generations of this battery use a urethane sealer and are more difficult to open and reseal.
The second battery is from a Volkswagen ID4. This battery was part of a VW customer service action 
that involved replacing specific battery modules that were identified as potentially defective. One of the items that made this battery interesting was the fact it was an 800-volt system. The students were able to see the use of arc-flash clothing when the battery was opened. Prior to removing the battery from the vehicle, specific pack data was gathered with the scan tool and used to pre-balance the new battery module. The battery was removed from the vehicle, and the suspect module was removed and replaced (See Figure 2 – ID4 Battery). The module replacement included the application of new heat transfer paste and the replacement of the internal bus bars and fasteners.
The third battery is from a Toyota Corolla Hybrid. This lithium battery is much smaller than the electric vehicle batteries (See Figure 3 – Toyota Corolla Battery). It is easy to remove and disassemble. It is a great battery for teaching the operation of internal components such as the contactors, recharge resistor, temperature 
sensors, and monitoring circuits. It also provides an example of a battery that is air cooled when discussing battery thermal management. The live data stream and the fault code diagnostics that Toyota provides for this vehicle makes it a great lab vehicle.
The Rivian battery was a great example of a battery not to use in class. Rivian does not service this battery in the field and replaces it as a unit when there is an internal problem. Although it is possible to remove individual modules, most of the battery contents are covered in a white polyurethane material that is designed to promote cooling and pack stability (See Figure 4 – Rivian Battery). This makes it virtually impossible to test anything outside of the control module. Additionally, the top battery cover was damaged beyond reuse when we removed it.
The last battery in the sequence is from a Mustang Mach-e. It was part of the recall for defective contactors. Removing this battery from the vehicle requires a special set of lift adapters that anchor the vehicle by grabbing the pinch welds. Once the cover is removed, the contactor assembly is easily replaced (See Figure 5 – Mach-e Battery). This battery is a great example of the process used to verify the cooling system and battery enclosure are properly sealed before reinstalling the battery.
Some of these activities and demonstrations would not have been possible without the generosity of our industry and dealership partners. These are organizations that go well beyond participating in advisory committee meetings. They realize their active participation in the program leads to graduates who are more prepared, and more likely to succeed, when they graduate.
Your activities will look different based on the components and vehicles you have available. The goal is to help the students identify issues involving capacity loss, internal resistance, imbalance, leakage, stored energy levels or another condition that affect battery performance and safety. These are failures that are becoming more frequent and need to be addressed in the field.
I will finish this article with the same offer I make after each of my presentations. If you are interested in getting started in the process of adding hybrid and electric vehicles to your curriculum or want more information, please feel free to reach out. I am more than willing to sit down in-person or online and share my experiences. Are you looking for a classroom textbook? Reach out to Pearson and ask for a review copy of the all-new Electric and Hybrid Electric Vehicle text that Jim Halderman and I co-authored. It is a comprehensive text covering all the latest information on the subject.