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Battery management systems (BMSs) for military systems require Fault-tolerance and Cyber Security

The vision for the future soldier is to be combat effective and also highly mobile, adaptive, networked, sustainable with total battle space situation awareness and information assurance. Therefore, he is equipped with night- vision goggles, radios, smartphones, GPS, infrared sights, a laptop as well as batteries to power them. Some of the missions the soldiers perform can take weeks, rather than days, without any ability to recharge; therefore he carries many spare batteries. Sometimes soldier carry seven types of batteries weighing up to 16 pounds for a 72-hour mission. All that weight slows down soldiers on foot, tethers them to constant resupply, and contributes to muscular and skeletal injuries caused by excessively heavy packs.


Powering all of this equipment is vital for success on the battlefield, however, they also add up to the weight, an infantry platoon currently carries about 700 pounds of batteries (17 pounds per soldier) for a 72-hour mission, according to the Army. In addition it is expensive, according to the U.S. Army Research Laboratory; a typical infantry battalion spends more than $150,000 on batteries alone each year, the second-highest expense next to munitions. Such high demand of power may not be fulfilled by batteries alone.


The major military organizations in the world are devising various ways for meeting enhanced power requirements, while also reducing the logistical load thereby enhancing soldier’s agility on the battlefield. Some of the solutions are developing smaller, lighter, cost-effective power sources, switching to renewable energy options, flexible solar panels, wearable energy solutions, nuclear batteries, low power electronics, battery and power management. 


As military platforms and systems such as land vehicles are fitted with more electronic equipment, their electrical energy demands will continue to increase and it is anticipated that their limited electrical energy storage capabilities (i.e. their batteries) will present issues during the vehicles’ life of type.  Furthermore, the development of hybrid electric vehicles (HEV) and electric vehicles (EV) has introduced new performance requirements on the batteries used in land vehicles.


Lightweight, long-lasting, fast, and field-rechargeable batteries are in heavy demand.  Because the rate at which chemicals within a battery react is dependent on temperature, reactions proceed more quickly as temperature increases. This means that, for military batteries, great care has to be taken to ensure that the power generated in a cold-weather environment is sufficient to meet a soldier’s needs.


On the other hand missions in high-temperature regions face overheating challenges. It is well known that certain battery cell chemistries, lithium-ion for example, are susceptible to overcharging and to over-discharging operational problems. Occurrences of these conditions and other events can cause a reduced useful battery life. In the extreme, destructive mishaps involving intense heat, fire, and even explosion can occur. Because a battery is an energy storage device, by definition a good battery contains large amounts of energy in a confined space.


Relying on flammable and combustible materials, current Li-ion batteries (LIBs) are susceptible to catastrophic fire and explosion incidents — most of which arrive without any discernable warning. Notably, Samsung Galaxy7 phones were banned from airlines because of this danger, and the Navy’s prohibition of e-cigarettes on ships and submarines is a direct response to the obvious need to reduce the flammability of the power source of choice for portable electronics, electric vehicles, and more.


To facilitate access and energy distribution for troops on the move, the Army and industry are working on Conformal wearable battery (CWB) and  “wearable” power generation devices that could be attached to a soldier’s vest or body armor. In the near future, soldiers will be carrying CWBs with a higher energy density than current models, However, the rise of higher-capacity cells raises another consideration, and that centers on preserving the safety of the soldiers. Consider what happens when these soldiers, with battery units worn close to their bodies, are involved in a firefight. If the CWB isn’t designed with the right safety features, it can endanger soldiers. When a battery case is punctured or crushed, the energy contained inside escapes. Escaping energy creates high heat in seconds, which transfers to the neighboring cells. Finally, as temperatures of the battery cells reach 800 degrees Celsius, the battery pack will ignite, or worse, explode.


One way to keep battery cells from exploding in combat and other dangerous situations involves applying chemical, mechanical and electrical engineering to create an anti-thermal propagation system that safeguards the soldier from fire. This can be accomplished by placing a thermal block between the battery cells to prevent the transfer of heat or thermal runaway. Another way is to do it through anti-flame suppression. That’s where the battery releases an anti-flame substance to prevent the escaping gases from reaching that explosion-inducing flashpoint.


Safety, therefore, is a paramount concern, and it must be established that Soldier Portable batteries (SPBs) will fail gracefully, i.e., without damaging other components of an electrical system or posing a danger to operators. Graceful failure must hold in the face of many different types of possible abuse. Requirements cover the testing necessary to establish the battery’s response to explosive decompression, submersion, thermal and mechanical shock, sand and dust storms, and numerous other environmental hazards that a military battery might encounter during its service life.


Battery management system (BMS)

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


A BMS may monitor the state of the battery as represented by various items, such as:

  • Voltage: total voltage, voltages of individual cells, or voltage of periodic taps
  • Temperature: average temperature, coolant intake temperature, coolant output temperature, or temperatures of individual cells
  • Coolant flow: for air or fluid cooled batteries
  • Current: current in or out of the battery

The BMS will also control the recharging of the battery by redirecting the recovered energy (i.e.- from regenerative braking) back into the battery pack (typically composed of a number of battery modules, each composed of a number of cells).


Army Maj. Ronald Schow, assistant program manager for soldier power at program executive office soldier said a conformable wearable battery (CWB) and power management system have been developed to simplify things for soldiers on the go. “Our power distribution system will triple charge all those other batteries that are on the ends of those radios, so all the soldier has to worry about is managing his conformable wearable battery in order to meet his mission requirements,” he said. The CWB and the connected power distribution system would result in a 17 percent net weight reduction for troops because they would need to carry fewer batteries, Schow said.


Thermal management

Battery thermal management systems can be either passive or active, and the cooling medium can either be air, liquid, or some form of phase change. Air cooling is advantageous in its simplicity. Such systems can be passive, relying only on the convection of the surrounding air, or active, utilizing fans for airflow. Commercially, the Honda Insight and Toyota Prius both utilize active air cooling of their battery systems. The major disadvantage of air cooling is its inefficiency. Large amounts of power must be used to operate the cooling mechanism, far more than active liquid cooling. The additional components of the cooling mechanism also add weight to the BMS, reducing the efficiency of batteries used for transportation.


Liquid cooling has a higher natural cooling potential than air cooling as liquid coolants tend to have higher thermal conductivities than air. The batteries can either be directly submerged in the coolant or the coolant can flow through the BMS without directly contacting the battery. Indirect cooling has the potential to create large thermal gradients across the BMS due to the increased length of the cooling channels. This can be reduced by pumping the coolant faster through the system, creating a tradeoff between pumping speed and thermal consistency


Fault-tolerant battery management system

Military systems require a fault-tolerant battery management system that includes redundancy, for applications including electric vehicles. A fault-tolerant battery management system comprises of the first set of electronic circuits and the second set of electronic circuits; each set for redundantly monitoring and managing a common plurality of interconnected battery cells; a controller for commanding and for collecting data from the first and second set of electronic circuits.


Portions of its circuitry are constituted in distinct fault domains with control, monitoring, and balancing of cells circuitry fault-effect-isolated from the circuitry associated with built-in real-time testing. Built-in tests are orchestrated in fault domains isolated from the functional circuitry being verified. These built-in tests provide test stimulus unique for each cell measurement. Cell balancing is performed in a fault-tolerant manner. It takes at least two independent faults, in two mutually distinct fault domains, to negatively affect balancing capability or to interfere with a redundant circuit’s ability to operate.


Texas Instruments Wireless Battery Management System

Recently, Texas Instruments  has revealed their new battery management system for electric vehicles. Unlike a traditional BMS, the new system removes the need for any control lines or sensing on the power cable itself and utilizes a wireless connection between the vehicle and charging station to transfer information.

The specially designed protocol allows for all data regarding the vehicle’s battery to be transmitted, and the system can provide information on more than 100 cells in milliseconds. Also stated by Texas Instruments is that the power consumed by the wireless chips is very low. According to a TI presentation, the main node of the system consumes 294uW while the individual devices consume 200uW.

Furthermore, the new system can work with multiple battery configurations, including 32, 48, and 60 cells. The safety has been confirmed by TÜV Süd in Germany, who is an independent safety testing service.

The  main advantage of a wireless BMS is the overall reduction of cables. Fewer cables mean that less can go wrong with physical wiring (such as strain and breakage), and therefore will potentially increase reliability. The advantage of reducing the overall number of wires used is reducing the weight of the vehicle. Electric vehicles are already trying to compete against fossil fuel cars on the range, and every kilogram removed from a vehicle helps improve the overall range. Thus, removing wires reduces the weight, and thereby requires less energy to move the car.


Wireless battery management systems also simplifies the construction of a vehicle. Traditional cell monitors are wired in series, but the use of dedicated communication cables quickly increases the design’s complexity. Thus, the use of a wireless system allows simplifying of the connection system. According to TI, another advantage is that the use of a wireless system simplifies the implementation of time-synchronized data. This may be due to the wireless system’s ability to read all cell voltages within a few milliseconds.


However wireless BMS also raises concerns of safety and cyber security.  Wireless systems do not have a direct physical link between the transmitter and receiver. This means that information is more likely to be lost in transit due to noise or external signals interfering.  If the connection between the BMS and the individual cells is prone to a connection failure, then the system’s safety is seriously compromised. Data regarding cell condition, voltage, temperature, and current draw is critical to the battery’s safe operation. Thus, using a potentially unreliable communication system means that there may be times when battery health cannot be read.


Wireless systems are far easier to hack than a wires system. Cybersecurity is becoming an increasing concern, and it is unlikely that a wireless system can ever be made unbreakable. An attacker who has access to the wireless network could feed in false information and potentially take control of the vehicle. While access to the steering wheel and breaks may not be possible, sending false readings could cause the car to shut down for safety reasons.



Cyber Security of BMS

The emerging Internet of Things (IoT) and cloud computing technologies are expected to advance the battery management systems (BMSs) by fully utilizing IoT wireless network, powerful computing, and unlimited cloud support, resulting in providing significant value in cost reduction, extended scalability, and greater visibility in the lithium-ion battery energy storage systems. However, IoT presents a growing threat from cyber-attacks as the IoT devices are always connected on networks.


Electric Vehicles (EV) like all modern vehicles are entirely controlled by electronic devices and networks that expose them to the threat of cyberattacks. Cyber vulnerabilities are magnified with EVs due to unique risks associated with EV battery packs. Compromised battery management systems such as the control of the voltage regulator could lead to cyberattacks that can either overdischarge or overcharge the pack. Overdischarge could lead to failures such as internal shorts in timescales of under an hour through cyberattacks that utilize energy-intensive EV subsystems like auxiliary components. Attacks that overcharge the pack could shorten the lifetime of a new battery pack to less than a year. Further, this also poses potential physical safety risks via the triggering of thermal (fire) events.


CSIRO partners with local battery-maker on ‘defence-grade’ management software

To decarbonise the grid, renewables need to replace coal and gas. Storage will act as a vital leveler of supply and demand. A battery-maker must be competitive and reliable. The opportunities for things to go awry multiply as storage is integrated into a multitude of systems, which includes the grid, building management systems, energy management systems, microgrids and so on.


As batteries slowly assume their role as integral suppliers of stability and services to their owners and the grid, the consequences of mismanagement – intentional or otherwise – will become severe. Australian lithium-ion battery manufacturer has partnered with the CSIRO to develop a defence-grade cybersecure battery management system (BMS) for its range of batteries. The software will include a cybersecurity layer that will allow encryption at both ends to protect the security of data transferred between the battery and client or monitoring service.


The $1.46 million BMS project is jointly funded by Energy Renaissance, the CSIRO and Innovative Manufacturing CRC, a not-for-profit, independent cooperative research centre. The battery management software will be exclusive to Energy Renaissance as part of its superStorage rack, a range of storage solutions in development that will include stationary applications (rack-based battery systems from about 50kWh to 5MWh to start with) and transport applications (buses, vans, light commercial).


CSIRO principal research scientist Adam Best has been seconded to Energy Renaissance to work on the project in addition to the Commonwealth government’s battery minerals roadmap that will incorporate Australian resources into the batteries that Energy Renaissance will produce. “The BMS is the brains of the battery,” Best tells EcoGeneration. “It controls the cells in terms of their charge and discharge profiles and gives information about state of charge and state of health, which is critical to the longevity of the product.”


An initial step, he says, is to work out what threats are worth guarding against and which ones are so challenging that they would make a BMS uneconomical. “Understanding the threat matrix, what we’re trying to exclude and … do that in an affordable and secure environment is critical.” Communicating through an inverter, the system will enable secure real time data, analytics and remote management to drive down the risk of battery failure and operating costs for grid-scale energy storage users.


Integrated Soldier Power and Data Systems (ISPDS)

ISPDS is a technology that is available today to help lighten the load (both weight and power) and make power management a more controlled, agile routine for dismounted soldiers. An ISPDS enables simultaneous connectivity and control over data transmission and power management of multiple wearable devices. This technology makes sure that soldiers have unequaled situational awareness on the battlefield to make better decisions on-the-spot in combat and thereby increase mission efficacy.


Increased combat effectiveness requires vast amounts of information and high-speed data to be exchanged, in real-time, between soldiers on the battlefield and command centers. Today’s soldiers are now also a means of data collection and exchange, well-appointed with communication systems, advanced weapons, data storage, navigation and other intelligence. When soldiers are dismounted, these solutions necessitate smart networking with each other and then, back to command centers.


Versatile ISPDS hubs can be used to manage both down (from command) and upstream data (to command) as a personal area network (PAN) backbone for field-deployed operations. A multitude of connection options including USB, fast Ethernet, Gigabit Ethernet and serial ports on a single hub that fits in the palm of your hand, creates a powerful, flexible communications hub that can connect and exchange data between wearables.


With the use of USB and power over Ethernet (PoE), the same ports that can help devices share data can also help to power and/or recharge them. While wearable devices have their own battery, a centralized power source, usually a lithium-ion battery, is carried to recharge those devices. And, of course, these lithium-ion batteries must be either replaced as they lose charge or recharged by an external power source—the preferred scenario to keep both individual and platoon burdens lower. In this later scenario, the ISPDS must be able to manage both the charge to each wearable device and the recharging of the lithium batteries.


Here is where power management can get much more complex than data management since it is a newer challenge to technologists. Recharging devices that connect via USB have a standard for sharing a charging profile via the “power manager” within the hub. Using either Linux on a chip or a microcontroller, the hub can determine which power profile these connected downstream devices need and will take the power from the battery and charge the wearable as needed. These standards have been in place for years and the job is straightforward.


Unfortunately, not all rechargeable batteries are alike. Each battery was developed without a power communications standard and thus has a different charging profile. In order to know how to properly recharge each battery, the charging profile can be hardcoded into the ISPDS hub, or the ISPDS hub can scan it and make a decision on which charging profile to use. That said, since each vendor might have its own nuances to achieve optimal charge performance, you need to program the specific battery type and charge profile into the ISPDS. Until charging profiles are standardized across batteries (i.e. data communications standards), ISPDS must have the intelligence to read charging profiles of the rechargeable batteries and then charge them accordingly to maximize them for mission longevity.


Next-generation ISPDSs use intelligent power management to prioritize energy supply for devices on the personal area network (PAN) and the battery life of the rechargeable batteries. Integrating with mission software, soldiers can have the information via visual statistics to decide whether to continue to use a specific device or shut it down to conserve battery and prioritize other devices more critically needed to complete the mission. This intelligent battery management can be managed via smartphone, tablet or laptop.

Integrated data and power management and charging capabilities that lighten the soldier’s required load work in two ways:

First, by integrating data networking and power management into one lightweight device, the number of devices a soldier must carry is reduced.

Second, by powering multiple devices with a central conformal battery, the need for each individual system to have its own battery is eliminated. Central batteries tend to be smaller, more lightweight and have a vast improvement on battery life.


Integrated Soldier Power and Data Systems deliver an immediate solution to the “battery fatigue” soldiers are dealing with every day. Recent interviews with soldiers on the front-line discuss all sorts of devices handed to them to help improve the mission. The reality is that we need to empower soldiers and provide them with the tools needed to make the mission manageable, without adding excess weight. Integrating power systems and controlling weight burdens before handing soldiers yet another new device is not only mission critical, but it ensures that wearable technologies designed to help soldiers don’t hinder them on the battlefield,  writes Ronen Isaac, General Manager, MilSource (El Segundo, CA).




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