Wednesday, November 6, 2024

What engineers need to know about current sensors for EV applications


Whether for the BMS or motor control, here are the key specs to understand when
sourcing these critical EV components.

Electric vehicles continue to grow in popularity and market share, and electric current is the fuel of the future. Current sensors are a critical component of today’s EVs, serving two primary applications according to Ajibola Fowowe, global offering manager at Honeywell.

“The battery management system (BMS) uses current sensors, in conjunction with other sensors such as the voltage and temperature sensors, to monitor the state of charge and overall health of the battery pack. The other use for current sensors is in motor control, where it is relied on to quickly detect and isolate a fault in the electric drive,” said Fowowe.

Regardless of the use case, there are several considerations EV engineers must understand when selecting among the many available current sensors. Here’s what you need to know.

Types of EV current sensors

There are different types of current sensors that each have advantages and disadvantages for EV applications.

Closed loop current sensors
Closed loop current sensors have a feedback system for improved measurement accuracy. A magnetic core concentrates the magnetic field generated by the flow of current and provides a proportional voltage to the amount of current detected in the core. This enables the sensor to generate a precise current measurement. Because of their high accuracy and stability, closed loop sensors are well suited for use in the BMS.

The Honeywell CSNV 500 (pictured above) is a closed loop current sensor rated for a primary current measurement range of ±500 amps of direct current. The CSNV 500 features a proprietary Honeywell temperature compensation algorithm with digital CAN output, to provide high accuracy readings within ±0.5% error over the temperature range of -40⁰ to 85⁰ C for robust system performance and reliability.

Open loop current sensors
Open loop current sensors operate on the principle of magnetic induction. They consist of a primary winding, through which the current travels, and a secondary winding that measures the induced voltage. Open loop sensors require less additional electronics and processing compared to closed loop sensors, resulting in faster response times. However, they require additional calibration because they are more prone to variations in heat and magnetic field. This means they are also less accurate — reaching approximately 2% error of the primary readings.

The fast response time of open loop current sensors makes them ideal for motor control functions. Motor control applications don’t require the same level of precision as the BMS, so the loss of accuracy compared to a closed loop or flux gate sensor isn’t critical.

The Honeywell CSHV line of open loop sensors have a range of 100 amps to 1,500 amps, and their response times are as fast as six microseconds. They are used in fault isolation and fault detection, as well as controlling motor speed. They can also be used in battery management systems that do not require very high accuracy, such as in hybrid electric vehicles. These sensors use AEC-Q100 qualified integrated circuits to meet high quality and reliability requirements.

The Honeywell CSHV series open loop sensor

Honeywell’s CSNV 1500 has both closed loop and open loop functionality. This enables the sensor to meet an accuracy requirement of 1%, and is designed for applications that require high accuracy. The CSNV 1500 is used for similar EV applications as the CSNV 500, as well as stationary energy storage systems and industrial operations.

Flux gate current sensors
Flux gate current sensors measure changes in the magnetic flux of a current as it passes through a magnetic loop, from which it can derive current measurements. The Honeywell CSNV 700 is designed for applications that fall between 500 A and 1,000 A requirements. It has a better zero-offset and higher sensing range than 500 amps sensors—but it also has higher power consumption than a closed loop sensor. The CSNV 700 has similar accuracy rating as the CSNV 500, at 0.5%, and it also uses AEC-Q100 qualified integrated circuits.

As with closed loop sensors, the flux gate sensor is best used in BMS settings that require high accuracy. When using flux gate sensors, however, engineers need to be mindful of their higher power requirements, which could consume more battery energy.

Honeywell’s CSSV 1500 is a combination open loop and flux gate sensor. It was designed to meet Automotive Safety Integrity Level C (ASIL-C) requirements for safety-critical applications where customers desire a higher level of reliability and performance. While many 1500 A sensors consume more power, the combination of open loop and flux gate technologies uses less power while still meeting the accuracy and functional safety requirements. It meets Automotive Safety Integrity Level C (ASIL C) requirements for safety critical applications. This requirement is typical of battery electric vehicles (BEV).

Shunt current sensors
A shunt current sensor measures the voltage drop across a sense resistor placed in the conduction path between a power source and a load. It is an inline current sensor connected directly to the busbar; closed loop, open loop and flux gate sensors are non-contact sensors that don’t have that direct connection.

One of the benefits of a shunt sensor is that it can provide an instantaneous measurement of current. However, it generates more heat and contributes to power loss in the circuit. This creates parasitic energy waste. Fowowe says that advancements in shunt technology is increasing its attractiveness in high voltage systems and Honeywell is actively researching additional value that can be derived from the application of shunt technology such as the potential combination of current and voltage measurements into one sensor to reduce the overall cost of the BMS.

Other key considerations for EV current sensors

In addition to considering which sensor to use in which application, engineers will also need to factor in other variables. Since the sensor needs to work properly in a magnetized environment, its capacity to handle magnetic interference is important. For BMS applications that rely on a high level of accuracy, engineers will need to consider the sensor’s zero-offset, which is the amount of deviation in output or reading from the lowest end of the measurement range.

Ease of integration is also important to consider. EVs can use either controller area network (CAN bus) standard or analog outputs. CAN communication is more common in the BMS. CAN bus communication speed is limited by the CAN protocol to 10 milliseconds, which is acceptable for the BMS. For more immediate measurements, motor control functions use analog outputs, which can respond in microseconds.

Another factor to be mindful of is the EV’s driving environment. EVs need to be able to function properly in any conditions, from a heat wave in Arizona to a snowstorm in New York. Therefore, the sensor’s operating temperature range needs to be factored in. According to Fowowe, Honeywell’s sensors are built to maintain performance in temperatures ranging from -40 to 85 degrees Celsius; the sensors feature a Honeywell patented multi-point temperature compensation algorithm to ensure the sensors can deliver very high accuracy and performance under any driving condition.

To learn more about current sensors for EVs, visit Honeywell at TTI.



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Tadano brings rough terrain electric crane to North America


Japanese crane manufacturer Tadano is introducing its fully electric EVOLT eGR-1000XLL-1 rough terrain crane in the US and Canada.

The new crane delivers the same lifting capability as its 100-ton rough-terrain GR1000XLL-4 in a quieter, zero-emissions package.

The eGR-1000XLL-1 offers up to seven hours of lifting or up to five hours of lifting plus 5.5 miles of jobsite travel powered by its on-board lithium-ion battery pack. The crane can be charged using standard 480 VAC grid power or a CCS1 fast charging system. Plug-in operation provides continuous crane operation, improving its efficiency.

The accompanying EVOLT App displays the battery status, operating history and journey distance for the operator, while the AML Control System provides crane control and monitoring through straightforward onboard diagnostics, improved settings and easily adjustable lifting limits.

Source: Tadano



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PPG develops new application method for battery pack fire protection coatings


US-based paint and specialty materials manufacturer PPG has developed a new method for applying battery fire protection coatings, called Intelligent Dynamic Non-Masking Airless Application (IDNMAA).

PPG says the battery fire protection coatings they developed are highly adaptable, enabling them to accommodate any battery pack design—an essential feature as packs become increasingly complicated.

IDNMAA technology merges the advantages of airless and flat stream methods, according to the company. While the traditional airless method is effective, it requires time-consuming masking and unmasking. The flat stream method eliminates the need for masking because of its precision but has longer cycle times, high film thickness in overlapping areas and bumps on the surface finish, resulting in material waste.

IDNMAA is designed to deliver both precision and efficiency, enabling rapid application and a smooth finish while reducing or eliminating the need for masking. This increases operational efficiency, minimizes waste and reduces costs related to manpower and material usage, the company explains.

Source: PPG



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Toshiba and partners testing electric buses with rapid pantograph charging system


Multinational electronics company Toshiba is partnering with Japanese bus operator Rinko Bus and Swiss electric bus equipment manufacturer Drive Electro Technology on a demonstration project to test the effectiveness of a rapid-charging battery powered by a pantograph to charge an electric bus in 10 minutes.

Drive Electro Technology will produce the pantograph charging system and convert a diesel bus to electric, powered by a Toshiba SCiB rechargeable battery. The pantograph charging facility is being installed in a bus depot in Kawasaki, south of Tokyo. Operation of the test bus on the city’s roads will begin in November 2025.

Used batteries installed in the pantograph charging system will be charged to reduce power consumption during peak demand and used to supply power to the onboard battery via the pantograph.

The project aims to take the lead in introducing the system in Asia to address the challenges of long charging times and the need for large charging spaces and numerous charging facilities that present barriers to widespread adoption of e-buses.

Source: Toshiba



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Tuesday, November 5, 2024

Seven cities form North American Electric Construction Coalition


Government officials from six cities in the US as well as Montreal, Canada have made a commitment to use more electric construction equipment in North America.

Leaders in the municipalities of Austin, Texas; Boulder County, Colorado; Los Angeles, California; Montréal, Canada; New York City; Philadelphia, Pennsylvania; and San Diego, California pledged to support pursuing programs and policies to advance the use of electric construction equipment wherever possible. Major capital construction entities, the signatories collectively spent more than $9.57 billion capital dollars in 2023 on purchased, rented or contracted construction equipment.

Some of the largest cities in the world are committed to advancing the goals of the Paris Climate Agreement through the increased use of electric construction equipment. As the market availability of electric construction equipment is nascent, the coalition can potentially spur the growth of the market in North America by taking steps to encourage its use.

For instance, The City of Austin is committed to reducing carbon emissions from municipal purchasing by 50% and is electrifying its fleet assets, which feature about 300 EVs. It has a goal of using EVs to travel 40% of total vehicle miles. Los Angeles has already made some purchases of all-electric equipment for city street services and construction and is taking steps to pilot contract language to support the use of electric equipment on public works projects.

“Although there is a robust market and infrastructure for electric construction equipment in certain cities around the world, the market needs significant growth in North American cities,” the officials said. “We want to leverage our role as leaders to build industry partnerships and create opportunities to develop the market for electric construction equipment in North America.”

“As suppliers increase market availability, signatories to this letter intend to purchase and/or use electric construction equipment on our projects wherever applicable and also intend to promote and pursue strategies that encourage the increased use of electric construction equipment in our contexts,” they added. “We call on suppliers to increase the availability of electric construction equipment and its supporting infrastructure and engage with this coalition.”

Source: North American Electric Construction Coalition



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General Motors to invest $625 million in new Lithium Americas JV


General Motors (GM) has entered into a new investment agreement with Lithium Americas to establish a joint venture (JV) to fund, develop, construct and operate the Thacker Pass lithium carbonate project in Humboldt County, Nevada.

GM will provide $430 million of direct cash funding and a $195 million letter of credit facility to support the construction of Phase 1 of Thacker Pass alongside a conditional commitment for a $2.3 billion US Department of Energy (DOE) loan announced earlier this year.

The GM financing can be used as collateral to support reserve account requirements under the DOE Loan. The JV transaction replaces a $330-million Tranche 2 common equity investment commitment from GM under its original investment agreement with Lithium Americas announced in January 2023, in which GM acquired 15 million shares in the developer.

Once the transaction is closed, GM will have a 38% interest and enter into an additional 20-year offtake agreement for up to 38% of production volumes from Thacker Pass Phase 2 and will retain its right of first offer on the remaining balance of Phase 2 volumes.

Detailed engineering at Thacker Pass continues to progress in advance of issuing full notice to proceed, and approximately 40% of the design is complete. Site preparation for major earthworks has been completed and approximately 50% of the process plant area has been excavated to prepare for concrete placement, which is forecast to begin by mid-2025.

“We’re pleased with the significant progress Lithium Americas is making to help GM achieve our goal to develop a resilient EV material supply chain,” said Jeff Morrison, SVP, Global Purchasing and Supply Chain at GM. “Sourcing critical EV raw materials, like lithium, from suppliers in the U.S., is expected to help us manage battery cell costs, deliver value to our customers and investors, and create jobs.”

Source: Lithium Americas



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24M Technologies reports battery separator innovations that can reduce battery fires


Lithium-ion battery technology developer 24M has released new testing data for its Impervio battery separator. The testing was related to the issue of battery-fire risk in EVs, energy storage systems and consumer applications.

The company’s Impervio battery separator was designed to reduce the risk of overcharging that can cause metallic dendrite formation and internal shorts, which can result in a battery fire and/or explosion. According to 24M, Impervio obstructs dendrite propagation and prevents thermal runaway by monitoring the cell’s electrochemistry and enabling the implementation of a failsafe in the event of a potential short.

24M’s lab tests compared performance between a 10 Ah high-nickel NMC/graphite pouch cell with an Impervio separator and another off-the-shelf nickel NMC/graphite pouch cell with a conventional separator. Both were fully charged and then advanced to 100% overcapacity. The cells with Impervio did not short or overheat with a full hour of overcharge, but the off-the-shelf cells overheated from dendrite-caused micro shorts within 15 minutes of overcharging and exploded into flames after 38 minutes.

The company expects to bring Impervio to market in 2025 or 2026.

“Battery safety is a major roadblock to the widespread adoption of EVs,” said Naoki Ota, 24M’s President and CEO. “A sustainable energy future is only possible with innovations like Impervio, which can help prevent battery fires and create new opportunities for battery innovation.”

Source: 24M



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What engineers need to know about current sensors for EV applications

Sponsored by TTI. Whether for the BMS or motor control, here are the key specs to understand when sourcing these critical EV components. ...