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July 24, 20234 min read

High-Voltage Charging Solutions for Non-Road Machinery

This is a summary from the presentation by the same title by Mourad Chergui, Sr. Product Manager at Delta-Q Technologies, at the Future of Electrification 2023 conference. Watch the full session here: 

Chergui began by saying that high-voltage charging solutions for non-road machinery are rapidly gaining traction in the industry. They offer significant advantages over traditional charging methods such as reduced resource usage, improved energy efficiency, and increased sustainability. These systems use thinner conductors, which helps to reduce the overall weight of the vehicle. Additionally, high-voltage charging systems require fewer conductors and less metal, making the vehicles more economical and environmentally friendly. The key principle behind high-voltage charging is to leverage direct current (DC) charging instead of alternating current (AC) charging, as it allows for more efficient power transfer. This reduces power losses and enhances performance.

The adoption of high-voltage charging solutions, specifically 800-volt systems, holds great promise for the non-road machinery industry. These solutions are designed with upcoming developments in mind and are well-positioned to meet the demands of battery technology. As advancements continue, the potential for higher-capacity batteries in future electric vehicles (EVs) is expected. By implementing high-voltage charging systems, non-road vehicles can be charged at a faster rate, reducing downtime and maximizing productivity on job sites. By embracing high-voltage charging solutions, the industry can ensure that its charging infrastructure remains compatible with evolving technology.

However, Chergui notes, a significant obstacle to the widespread adoption of 800-volt systems is the limited availability of 800-volt DC charging stations. While there are over 400,000 publicly accessed fast chargers worldwide, very few support 800 volts. This is a significant impediment to the rapid expansion of 800-volt architecture in automotive applications that rely heavily on public charging infrastructure. The good news is that most EV charging station manufacturers have started future-proofing their DC charging systems by increasing the upper limit of the voltages. Industrial and commercial operators, who do not typically rely on public charging stations, have their own private charging infrastructure and could easily use new EV charging stations that support 800 volts.

There are also additional challenges and considerations associated with the transition to 800-volt systems. The new generation of semiconductors improves the efficiency of electric motors but also increases the stress on the components and insulation system due to electrical arcing, also known as partial discharges. This necessitates the use of more robust fuses, cable insulation, plugs, and contactors, which often need to be redesigned to meet the specifications of newer systems. There is also an increase in electromagnetic compatibility challenges, and the system requires more complex thermal management, especially within the battery compartment. Inside the batteries themselves, there is an increase in stress on the components. The availability of materials and components designed for 800-volt systems is limited. When these components are available, they often have very high entry prices, making them less accessible.

To ensure safety, high voltage interlock loops (HVIL) are used. They immediately notify the system and disconnect the high voltage system in the presence of any potential danger. Some systems employ pre-charge mechanisms to prevent the sudden large inrush of currents from moving through the power system when it's turned on, which could otherwise cause significant damage and pose risks for those working with the system. Bleed-off resistors may be necessary to safely discharge any remaining voltage after disconnection, considering the high levels of capacitance in high-voltage systems. 

The high voltages and noisy environment in the drive systems require robust and high-performance galvanic isolation to ensure safe and reliable operation. Often the creepage distances and insulation resistance need to be doubled compared to 400-volt systems. In particular, there is a need for developing and producing a class of 800-volt EV cables capable of properly handling voltages up to 1,000-volt peaks. Continuous monitoring of insulation, voltage levels, and resolution loss is a significant challenge in these systems. Early detection and interruption of insulation faults is essential. Faults in the insulation system during normal operation can be caused by various factors such as contamination, salt, humidity, faulty connectors, or beam influences.

In the Q&A session following the presentation, Chergui was asked what he saw as the future of off-road equipment charging, away from any public charging infrastructure. He believes that the future of charging non-road machinery lies in private charging stations. For example, EV charging stations, especially mobile transportable ones that can be connected by an electrician on the site, can be temporarily installed until the job is finished on the job site and then moved to another location. These chargers will be tailored to meet the unique requirements of off-road equipment, considering factors such as charging speed, power demands, environmental conditions, and integration with onboard telematics systems. By providing specialized charging solutions, these dedicated chargers can optimize the charging process and enhance the overall performance of off-road equipment. These charging stations offer the robustness and safety necessary for today's job site.

The rapid development of technologies and components supporting high-voltage powertrain architecture is driving the electrification of heavy machinery. Manufacturers venturing into this space need to consider many aspects related to system architecture, design, component selection, safety, regulations, reliability, and serviceability. The 800-volt architecture is emerging to provide the ultimate performance for heavy mobile equipment. The industry is actively addressing the implementation issues and is paving the way to full electrification at all category and size levels of construction equipment.