Smart Battery Management System

 Smart Battery Management System

A battery management system (BMS) is any electronic system that manages a rechargeable battery (cell or battery pack), such as by protecting the battery from operating outside its safe operating area, monitoring its state, calculating secondary data, reporting that data, controlling its environment, authenticating it and / or balancing it.

A battery pack built together with a battery management system with an external communication data bus is a smart battery pack. A smart battery pack must be charged by a smart battery charger.

Smart Battery System (SBS) is a specification for managing a smart battery, usually for a portable computer. It allows operating systems to perform power management operations via a smart battery charger based on remaining estimated run times by determining accurate state of charge readings. Through this communication, the system also controls the battery charge rate. Communication is carried over an SMBus two-wire communication bus. The specification originated with the Duracell and Intel companies in 1994, but was later adopted by several battery and semiconductor makers.

The Smart Battery System defines the SMBus connection, the data that can be sent over the connection (Smart Battery Data or SBD), the Smart Battery Charger, and a computer BIOS interface for control. In principle, any battery operated product can use SBS.

• A special integrated circuit in the battery pack (called a fuel gauge or battery management system) monitors the battery and reports information to the SMBus. This information might include battery type, model number, manufacturer, characteristics, charge/discharge rate, predicted remaining capacity, an almost-discharged alarm so that the PC or other device can shut down gracefully, and temperature and voltage to provide safe fast-charging.

Battery Management System

Battery management system (BMS) is technology dedicated to the oversight of a battery pack, which is an assembly of battery cells, electrically organized in a row x column matrix configuration to enable delivery of targeted range of voltage and current for a duration of time against expected load scenarios.

How do battery management systems work?

Battery management systems do not have a fixed or unique set of criteria that must be adopted. The technology design scope and implemented features generally correlate with:

• The costs, complexity, and size of the battery pack
• Application of the battery and any safety, lifespan, and warranty concerns
• Certification requirements from various government regulations where costs and penalties are paramount if inadequate functional safety measures are in place

There are many BMS design features, with battery pack protection management and capacity management being two essential features. We’ll discuss how these two features work here. Battery pack protection management has two key arenas: electrical protection, which implies not allowing the battery to be damaged via usage outside its SOA, and thermal protection, which involves passive and/or active temperature control to maintain or bring the pack into its SOA.

The importance of battery management systems

Functional safety is of the highest importance in a BMS. It is critical during charging and discharging operation, to prevent the voltage, current, and temperature of any cell or module under supervisory control from exceeding defined SOA limits. If limits are exceeded for a length of time, not only is a potentially expensive battery pack compromised, but dangerous thermal runaway conditions could ensue. Moreover, lower voltage threshold limits are also rigorously monitored for the protection of the lithium-ion cells and functional safety. If the Li-ion battery stays in this low-voltage state, copper dendrites could eventually grow on the anode, which can result in elevated self-discharge rates and raise possible safety concerns. The high energy density of lithium-ion powered systems comes at a price that leaves little room for battery management error. Thanks to BMSs, and lithium-ion improvements, this is one of the most successful and safe battery chemistries available today.

Performance of the battery pack is the next highest important feature of a BMS, and this involves electrical and thermal management. To electrically optimize the overall battery capacity, all the cells in the pack are required to be balanced, which implies that the SOC of adjacent cells throughout the assembly are approximately equivalent. This is exceptionally important because not only can optimal battery capacity be realized, but it helps prevent general degradation and reduces potential hotspots from overcharging weak cells. Lithium-ion batteries should avoid discharge below low voltage limits, as this can result in memory effects and significant capacity loss. Electrochemical processes are highly susceptible to temperature, and batteries are no exception. When environmental temperature drops, capacity and available battery energy roll off significantly. Consequently, a BMS may engage an external in-line heater that resides on, say, the liquid cooling system of an electric vehicle battery pack, or turn-on resident heater plates that are installed underneath modules of a pack incorporated within a helicopter or other aircraft. Additionally, since charging of frigid lithium-ion cells is detrimental to battery life performance, it is important to first elevate the battery temperature sufficiently. Most lithium-ion cells cannot be fast-charged when they are less than 5°C and should not be charged at all when they are below 0°C. For optimum performance during typical operational usage, BMS thermal management often ensures that a battery operates within a narrow Goldilocks region of operation (e.g. 30 – 35°C). This safeguards performance, promotes longer life, and fosters a healthy, reliable battery pack.

The benefits of battery management systems

An entire battery energy storage system, often referred to as BESS, could be made up of tens, hundreds, or even thousands of lithium-ion cells strategically packed together, depending on the application. These systems may have a voltage rating of less than 100V, but could be as high as 800V, with pack supply currents ranging as high as 300A or more. Any mismanagement of a high voltage pack could trigger a life-threatening, catastrophic disaster. Consequently, therefore BMSs are absolutely critical to ensure safe operation. The benefits of BMSs can be summarized as follows.

• Functional Safety. Hands down, for large format lithium-ion battery packs, this is particularly prudent and essential. But even smaller formats used in, say, laptops, have been known to catch fire and cause enormous damage. Personal safety of users of products that incorporate lithium-ion powered systems leaves little room for battery management error.
• Life Span and Reliability. Battery pack protection management, electrical and thermal, ensures that all the cells are all used within declared SOA requirements. This delicate oversight ensures the cells are taken care of against aggressive usage and fast charging and discharging cycling, and inevitably results in a stable system that will potentially provide many years of reliable service.
• Performance and Range. BMS battery pack capacity management, where cell-to-cell balancing is employed to equalize the SOC of adjacent cells across the pack assembly, allows optimum battery capacity to be realized. Without this BMS feature to account for variations in self-discharge, charge/discharge cycling, temperature effects, and general aging, a battery pack could eventually render itself useless.
• Diagnostics, Data Collection, and External Communication. Oversight tasks include continuous monitoring of all battery cells, where data logging can be used by itself for diagnostics, but is often purposed to the task for computation to estimate the SOC of all cells in the assembly. This information is leveraged for balancing algorithms, but collectively can be relayed to external devices and displays to indicate the resident energy available, estimate expected range or range/lifetime based on current usage, and provide the state of health of the battery pack.
• Cost and Warranty Reduction. The introduction of a BMS into a BESS adds costs, and battery packs are expensive and potentially hazardous. The more complicated the system, the higher the safety requirements, resulting in the need for more BMS oversight presence. But the protection and preventive maintenance of a BMS regarding functional safety, lifespan and reliability, performance and range, diagnostics, etc. guarantees that it will drive down overall costs, including those related to the warranty.

The BMS may fulfill a variety of functions depending on the particular application as well as the type and size of the battery. The main goal of BMS is to keep the battery within the safety operation region in terms of voltage, current, and temperature during the charge, the discharge, and in certain cases at open circuit. In this way, the battery will serve the application as long as possible in the most predictable way without creating any threat menacing the energy system and the nearby people (inhabitants, staff, maintenance, etc.). This part of BMS may be referred as charge and discharge management. Additionally, BMS may analyze the battery behavior in a continuous or periodic manner transforming the monitored parameters into battery state data which are fed to the upper system level or are directly used to control the charge and the discharge processes on a feedback principle. The upper system level can be the battery user itself (like a driver of an electric car) or a software/hardware configuration controlling the energy system. Depending on the obtained battery state data, the user can choose and execute a given decision which can be reduced often to a simple termination or restart of the charge or the discharge process.

The batteries and the corresponding BMS can be divided into two main categories—aqueous electrolyte batteries and nonaqueous electrolyte batteries. The operation of the energy storage reactions in the aqueous electrolyte batteries is usually accompanied by the electrochemical reactions of water decomposition—hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). HER and OER are referred to as parasitic processes leading to loss of water, decrease of the Faradic and energy efficiency, as well as progressive battery degradation. The management of aqueous electrolyte batteries is focused on finding the right balance between the charge/discharge reactions and the water loss processes.

FEATURES

• Software development using Model Based Design (MBD) approach
• Monitoring of every cell Voltage , pack current and temperature
• Cell balancing (Passive)
• Advanced Estimation Techniques for State of Charge (SoC) and State of Health (SoH)
• Advanced Estimation Techniques for State of Power (SoP) and State of Safety (SoS)
• Active Monitoring and Derating
• Thermal Management
• Compatible with wide range of lithium-ion cells
• Failure detection and Diagnostics
• Modular and Scalable Architecture
• State of Art GUI for Monitoring, Configuration and Calibration

APPLICATION

• Applicable for 2w/3w/4w Electric and Hybrid Electric Vehicles
• Applicable for fuel cell and Ultra capacitor based systems
• Applicable for Energy Storage Systems
• Applicable for Agricultural and Off Road vehicles
• Applicable for Unmanned aerial vehicle (Drones)