At the Battery Show, Sensata Technologies leading supplier of electrical protection, sensing, control, and power management solutions, unveiled the Lithium Balance n3-BMS, a brand-new battery management system (BMS) for high voltage applications. Specifically for battery manufacturers and producers of buses, electric trucks, and other heavy commercial vehicles, the Lithium Balance n3-BMS is designed for applications with power up to 1,000 volts/2,000 amps.
As electric commercial vehicle OEMs and battery packers focus on functional safety in their platforms while aiming for a quicker time to market, the demand for ISO 26262 certified components is increasing. The ISO 26262 certification procedure is difficult, expensive, and may take years to complete. The development time and associated costs can be decreased using an off-the-shelf, Automotive Safety Integrity Level (ASIL) C-certified solution like the Lithium Balance n3-BMS.
According to Sensata Technologies, the n3-BMS’s layered software architecture allows customers to modify the battery management system using their code and algorithms without jeopardizing the ASIL C certification. An External Software Layer (ESW) and Base Software Layer (BSW), connected by an open API link layer, comprise the BMS software architecture. Since the BSW layer of the software contains all the safety-critical BMS functionalities, developers are free to use their software code and algorithms in the ESW without jeopardizing the system’s ISO 26262 certification.
The Lithium Balance n3-BMS and its predecessor, the n-BMS, are distributed systems made up of a Master Control Unit (MCU), which gathers information and manages battery operations, and up to 30 Cell Monitoring Units for monitoring individual cells. It is simple to enhance from n-BMS to n3-BMS with the substitute of a single PCB board in a battery system of any size because the n-BMS’ MCU is compatible with the n3-BMS’ CMUs. This offers an easy and affordable way to upgrade to an ASIL C-certified BMS for developers of next-generation, heavy electric vehicles who anticipate the requirement for an ISO 26262-certified system in the future (available early 2023).
Battery Management System Growth
Battery management systems’ job is to make sure that a battery’s remaining energy is used as efficiently as possible. BMS systems shield batteries from deep discharge and over-voltage, caused by extremely fast charging and extremely high discharge current, to prevent overloading the batteries. To ensure that different battery cells have the same charging and discharging requirements, the battery management system also offers a cell balancing function in the case of multi-cell batteries.
The battery management system market in 2021 was worth USD 6.41 billion, and it will be worth USD 35.79 billion by 2030, growing at a 21.2% CAGR during 2021-2030. Electronic control circuits known as battery management systems (BMS) are used to monitor and manage the charging and discharging of batteries.
Electric Vehicle will drive advancements in BMS
The automotive industry will dominate future demand for battery systems. These include internal combustion engines (ICEs) with a start/stop technology (typically 48 Volt systems), full battery electric vehicles (400 Volt and up, BEVs), and mild hybrid 48V battery-driven and hybrid EVs. Less than 5% of new vehicle sales in 2022 were electric vehicles, but by 2030, many automakers anticipate that percentage to rise to 50%. As a result, one of the most rapidly expanding segments for several semiconductor manufacturers is electric vehicle technology.
The adoption of electric vehicles depends on a few key deliverables, the first of which is the requirement for better BMS, which impacts driving range. The customer can achieve a greater variety from the same battery pack with a more precise battery management system. For instance, the battery is charged nearer to its maximum storage level if the BMS can detect it with an accuracy of 1% or higher. Like guard-banding, the battery is used between 15 and 85% of its capacity with a 5% margin for error. Guard-banding the battery’s usable charge would be unnecessary if the BMS were more accurate. Therefore, reducing the error from 5% to 1% permits the use of 8% more of the stored charge, resulting in more miles per charge.
Additionally, an accurate state of charge (SOC) increases range projection accuracy while maintaining battery safety (preventing catastrophic failure) and allows better battery utilization from a safety and reliability standpoint. A smaller, lighter battery pack can be used with increased battery usage and effectiveness, lowering the vehicle’s cost.
A few trends are evolving in response to the batteries used in electric vehicles. The first is better accuracy, which translates to longer battery life and gradual cell aging. Improved “fuel gauge” accuracy also increases driver confidence and safety.
The demand for extra channels of frontend ADC and cell balancing pins per battery management system device is driven by the second major trend, which is that battery stacks are moving toward higher voltages, necessitating more cells in a stack. Currently, most battery cells operate at 400 volts or less, though some performance EVs already use 800 volt systems. In the near future, these levels are anticipated to increase to 1000+ Volts, resulting in faster charging that will enable EVs to achieve recharging times that are more similar to the time required to refuel an internal combustion engine. With the ability to now improve a battery pack, these capabilities give semiconductor suppliers a competitive edge.
ATE Testing Challenges
For manufacturers of automated test equipment (ATE), these developments in battery management systems pose new difficulties. The BMS’s increased accuracy presents the first obstacle. A significant proportion of the usable area falls along a rigid curve when a battery’s discharge curve is measured. The full Li-ion state of charge range from SOC 100-0% From 4.3V, i.e., fully charged, down to 2.2V i.e. discharged.
An average Li-ion discharge uses 80–20% or 90–10% of the battery’s capacity. The SOC voltage is relatively flat at 3.75–3.65V (100mV total or 1.7mV / 1% SOC Change) in the 80–20% region. This describes why BMS suppliers are looking into measurement accuracy of 100uV or 50uV in the 5V range.
The second difficulty is that, to mimic a stack of battery cells, the BMS device, which can include 16 to 24 cells or more, must be biased with common mode voltages. Due to this, the ATE must provide dense, high-precision, low-noise floating voltage/current sources (VIs). A high-precision measurement system must typically be multiplexed to all cell pins and the device’s corresponding discharge pins due to the testing nature of these devices. Suppose the ATE system does not have enough internal matrices. In that case, this may necessitate a huge amount of relays on the device interface board, necessitating a very large application space on the DIB.
In order to meet the demands of the automotive market, batteries and BMS devices are evolving. New test methodologies will be required as a result of these improvements. There will be numerous challenges in a short period, ranging from 1000+ Voltage systems to new battery chemistries. In order to keep up with the BMS requirements and deliver affordable solutions at large numbers of sites, ATE providers will need to build new tester capacity with quick production ramps.