Browse technical resources about solar mounting systems, tracker technology, structural design, and installation best practices.
HOME / Overcharging A Lithium Battery Risks, Prevention, And - BeTheFuture Solar Foundation & Infrastructure
One of the most common types of batteries is lithium-ion. Due to this battery's lightweight and rechargeable nature, it is often used in laptops, smartwatches and mobile phones. However, lithium-ion batteries can be dangerous. When exposed to high temperatures, lithium-ion batteries have been known to overheat. Another common type of battery is Alkaline. These are used in small electronic devices and comes in many different shapes and sizes, including AAA and AA. There are no. Car batteries cannot be sent through our network – either within the UK or internationally. For a full list of restricted items, take a look at our prohibited items page. These are some of. As standard, we provide £50 of contents cover on all parcels sent within the UK. However, if you are sending a higher value electrical item, for example, a laptop or mobile phone, we recommend taking out extended contents cover. Due to their hazardous nature, parcels containing batteries must be packaged carefully to avoid damage during transit. When sending a battery in.
[PDF Version]When preparing shipments containing lithium batteries, it is important to ensure the batteries are not in any way defective, damaged, or have the potential to produce a dangerous evolution of heat, fire or short circuit. When packaging lithium batteries for shipment, strong rigid outer packaging must be used.
At PACK & SEND we can provide you with a complete packing and delivery service for lithium battery-powered equipment within the constraints of international regulations but be aware that this is a specialist and costly service and not appropriate for domestic lithium batteries not contained in their equipment.
When exposed to high temperatures, lithium-ion batteries have been known to overheat and even explode. For this reason, we have some restrictions when sending lithium-ion batteries through our network. You can send lithium-ion batteries within the UK, as long as the battery is fitted within the device.
Your items can safely be shipped with any courier service. Now, lithium and lithium-ion batteries are a much different story. Their shipping is tightly regulated by IATA (International Air Transport Association), as well as individual postal services in various countries.
THIS WILL ALMOST ALWAYS MAKE IT UNECONOMIC TO SEND LITHIUM BATTERIES ON THEIR OWN. For deliveries of shipments with lithium batteries included in the equipment to an overseas destination - be they laptops, mobile phones or more specialist equipment - trust us to get your shipments to their destination without the risk of problems arising.
FedEx adheres to IATA regulations for shipping lithium batteries by air and ADR regulations for shipping lithium batteries by road in Europe. Regulations on how to ship lithium batteries vary depending on which type you are shipping. Typically found in watches and cameras, they contain metallic lithium and are also called primary lithium batteries.
If neither the charger nor the protection circuit stops the charging process, then more and more energy enters the cell. As a result, the voltage in the cell rises – this is known as over-charging.
Liu et al. found that the cell thermal stability decreased gradually as lithium-ion batteries aged with slight overcharge cycling. Compared with slight overcharge, deep overcharge can make lithium-ion batteries complete failure and cause thermal runaway, resulting severe safety hazards such as fire and explosion.
Overcharging can happen for several reasons. Sometimes, it may be due to an incorrect charger that continues charging at the right time. Other times, it may occur because of a malfunction in the device's charging system. Regardless of the cause, overcharging can significantly affect the battery's performance and safety. Part 2.
In this paper, the overcharge performance of a commercial pouch lithium-ion battery with Li y (NiCoMn) 1/3 O 2 -Li y Mn 2 O 4 composite cathode and graphite anode is evaluated under various test conditions, considering the effects of charging current, restraining plate and heat dissipation.
Rupture of the pouch and separator melting are the two key factors for the initiation of TR during overcharge process. Therefore, proper pressure relief design and thermal stable separator should be developed to improve the overcharge performance of lithium-ion batteries.
The overcharge-induced TR process of lithium-ion batteries is an electrochemical-thermal coupled process accompanied with ohmic heat generation, gas generation and a series of exothermic reactions .
This situation is mainly caused by lithium plating. The plated lithium can react with the electrolyte at a lower temperature, and the thermal stability of the side reaction products is lower. However, when the overcharge exceeds V p, the cell temperature is higher.
Li-ion battery technology uses lithium metal ions as a key component of its electrochemistry. Lithium metal ions have become a popular choice for batteries due to their high energy density and low weight. One n. Li-ion batteries have many applications in the real world aside from simply running the apps. Whatever you need a Li-ion battery for, you can rely on its durability, rechargeability, safety, and long-lasting power supply. Lithium batteries have become a vital part of our everyday li.
Rechargeable lithium-ion batteries have become incredibly popular for smartphones, laptops, personal digital assistants (PDAs), and other portable electronic devices. There are many reasons why so many manufacturers have adopted rechargeable Li-ion batteries, for example: Li-ion batteries used in watches are small.
Rechargeable lithium-ion batteries incorporating nanocomposite materials are widely utilized across diverse industries, revolutionizing energy storage solutions. Consequently, the utilization of these materials has transformed the realm of battery technology, heralding a new era of improved performance and efficiency.
Lithium-ion batteries have garnered significant attention, especially with the increasing demand for electric vehicles and renewable energy storage applications. In recent years, substantial research has been dedicated to crafting advanced batteries with exceptional conductivity, power density, and both gravimetric and volumetric energy.
Handheld power tools commonly use lithium-ion batteries as well. Drills, saws, sanders – they all run on rechargeable lithium packs. The high energy density of lithium allows compact battery designs that don't add much bulk. And they deliver enough power and runtime for job site use.
Digital cameras were another early mass market product to use lithium-ion batteries. Their rechargeable nature eliminated the need to constantly buy disposable batteries. Higher capacity lithium batteries now provide DSLR cameras battery lives measured in hundreds of shots per charge.
The low self-discharge rate of a typical lithium-ion battery is ten times lower than a traditional lead-acid battery. Lithium batteries are the ideal solution if a system is not continually in use. People with mobility issues have found new freedom thanks to rechargeable lithium-ion batteries.
Although different types of lithium batteries offer varying degrees of water resistance, they should never be submerged in water. Submerging any battery in water may significantly damage it.
Water can have detrimental effects on lithium batteries, posing safety risks and compromising battery performance. Safety Considerations: Understanding the importance of proper use, handling, and storage of lithium batteries helps prevent accidents and ensures worker safety.
When water infiltrates a lithium battery, it instigates a series of detrimental reactions that can lead to heat generation, hydrogen gas release, and potential fire hazards. Upon contact with water, lithium batteries swiftly display signs of malfunction, including heat generation and the emission of smoke.
Water Contamination: When lithium batteries get wet, water contamination can occur, leading to potential damage. Water can react with the battery components, causing irreparable harm. Minor Splashing: Minor splashing or exposure to water may not immediately kill lithium batteries.
Fire Hazard Lithium-ion batteries are highly susceptible to catching fire when submerged in water. The water can cause the battery to short circuit, and as the battery heats up, it may ignite. Even worse, water cannot extinguish a lithium battery fire. Instead, it can exacerbate the flames, making the situation far more dangerous.
To prevent risks, keep lithium batteries dry. If a lithium battery gets wet, remove it from water, avoid charging or using it, gently dry it, and consider safe disposal if damaged. Corrosion and Short Circuits: When water infiltrates lithium batteries, it can cause corrosion and lead to short circuits.
Safety Precautions: To prevent water damage to lithium batteries, it is important to handle them with care and avoid exposing them to water. Proper storage, handling, and protection from moisture are essential to maintain the integrity and safety of lithium batteries.
A commonplace chemical used in water treatment facilities has been repurposed for large-scale energy storage in a new battery design by researchers at the Department of Energy's Pacific Northwest N.
Authors to whom correspondence should be addressed. Lithium iron phosphate (LFP) batteries have emerged as one of the most promising energy storage solutions due to their high safety, long cycle life, and environmental friendliness.
Lithium iron phosphate battery has a high performance rate and cycle stability, and the thermal management and safety mechanisms include a variety of cooling technologies and overcharge and overdischarge protection. It is widely used in electric vehicles, renewable energy storage, portable electronics, and grid-scale energy storage systems.
A lifetime in the car business, first engineering, now communicating BMW iX being tested with prototype Our Next Energy lithium iron phosphate battery Lithium iron phosphate (LFP) batteries already power the majority of electric vehicles in the Chinese market, but they are just starting to make inroads in North America.
Learn more. In recent years, the penetration rate of lithium iron phosphate batteries in the energy storage field has surged, underscoring the pressing need to recycle retired LiFePO 4 (LFP) batteries within the framework of low carbon and sustainable development.
In addition, lithium iron phosphate batteries have excellent cycling stability, maintaining a high capacity retention rate even after thousands of charge/discharge cycles, which is crucial for meeting the long-life requirements of EVs. However, their relatively low energy density limits the driving range of EVs.
Lithium manganese iron phosphate (LiMn x Fe 1-x PO 4) has garnered significant attention as a promising positive electrode material for lithium-ion batteries due to its advantages of low cost, high safety, long cycle life, high voltage, good high-temperature performance, and high energy density.
Yes! When a battery pack 'goes bad' it's usually because the BMS has decided to shut it off for one of many reasons. This is why it's a good idea to disassemble lithium-ion battery packs for its cells. In most other cases, just a single cell has failed. Remember, battery packs are made of many cells that are grouped in a specific. Lithium-ion battery packs are spot welded together. So it's no small feat to separate the cells. In fact, breaking down a lithium-ion battery pack is a rather. When breaking down a lithium-ion battery pack, having the right tools for the job is critical. The tools you use to disassemble a lithium-ion battery pack can be the difference between. If you are wondering how to remove cells from lithium-ion battery packs, the first answer is 'Very carefully.' A BMS protects a battery pack (and the user) from 99 percent of things that can cause fire and serious injury. When you. Your work area should be somewhere that is clean, well-ventilated, and far away from any flammable materials or liquids. Make sure your work surface is.
[PDF Version]When breaking down a lithium-ion battery pack, having the right tools for the job is critical. The tools you use to disassemble a lithium-ion battery pack can be the difference between salvaging a bunch of great cells and starting a fire. 5 pack of flush cut pliers. Perfect for removing the nickel strip that is attached to cells when salvaging.
Taking apart a lithium-ion battery pack may appear challenging at first, but with a solid approach and some patience, anyone can do it. It's super important to understand the connections between battery cells and to recognize the potential risks, like shoulder shorts.
The first step to take before dismantling a Li-ion battery is to identify its type and the amount of charge remaining in it. This information is critical because different types of batteries require different handling procedures. Additionally, the risks associated with dismantling the battery increase with the charge level.
It generally means that the other cell groups are just fine. Lithium-ion battery packs are spot welded together. So it's no small feat to separate the cells. In fact, breaking down a lithium-ion battery pack is a rather involved process that takes care and patience. You have to be extremely careful when breaking down a lithium-ion battery pack.
When it comes to disassembling a battery, the first important step is removing the battery cover or casing. This outer layer provides protection to the internal components of the battery and prevents any damage from external factors. By following a few simple steps, you can safely remove the cover or casing without causing harm.
Before you start the process, gather the following items: 1. Safety glasses: Protect your eyes from any potential sparks or debris that may fly off during disassembly. 2. Gloves: Wear gloves to safeguard your hands from accidental cuts or exposure to harmful chemicals present in some batteries.
The increase in battery demand drives the demand for critical materials. In 2022, lithium demand exceeded supply (as in 2021) despite the 180% increase in production since 2017. In 2022, about 60% of lithium, 30% of cobalt and 10% of nickel demand was for EV batteries. Just five years earlier, in 2017, these. In 2022, lithium nickel manganese cobalt oxide (NMC) remained the dominant battery chemistry with a market share of 60%, followed by lithium iron phosphate (LFP) with a share of just. With regards to anodes, a number of chemistry changes have the potential to improve energy density (watt-hour per kilogram, or Wh/kg). For example, silicon can be used to replace all or some of the graphite in the anode in order to make it lighter and thus increase.
In 2022, the global shipment of battery for energy storage hit 142.7 GWh, a surge by 204.3% from 2021's 46.9 GWh. The top 3 largest manufacturers each shipped more than 10 GWh, increasing multiple times compared with the previous year.
Total installed grid-scale battery storage capacity stood at close to 28 GW at the end of 2022, most of which was added over the course of the previous 6 years. Compared with 2021, installations rose by more than 75% in 2022, as around 11 GW of storage capacity was added.
The total volume of batteries used in the energy sector was over 2 400 gigawatt-hours (GWh) in 2023, a fourfold increase from 2020. In the past five years, over 2 000 GWh of lithium-ion battery capacity has been added worldwide, powering 40 million electric vehicles and thousands of battery storage projects.
Today's energy storage installations may seem minimal compared to what they are expected to be in 2030, but they have been growing fast already. New energy storage capacity in 2022 was 60% higher than in the year before. 43 GWh were added last year. This year, 74 GWh are expected to be added, which would be 72% more than last year.
In July 2021 China announced plans to install over 30 GW of energy storage by 2025 (excluding pumped-storage hydropower), a more than three-fold increase on its installed capacity as of 2022.
Automotive lithium-ion (Li-ion) battery demand increased by about 65% to 550 GWh in 2022, from about 330 GWh in 2021, primarily as a result of growth in electric passenger car sales, with new registrations increasing by 55% in 2022 relative to 2021.
A battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative). The anode and cathode store the lithium. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions. While the battery is discharging and providing an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When plugging in the device, the opposite. The two most common concepts associated with batteries are energy density and power density. Energy density is measured in watt-hours per kilogram (Wh/kg) and is the amount of energy the battery can store with.
This means that during the charging and discharging process, the lithium ions move back and forth between the two electrodes of the battery, which is why the working principle of a lithium-ion battery is called the rocking chair principle. A battery typically consists of two electrodes, namely, anode and cathode.
What happens in a lithium-ion battery when charging (© 2019 Let's Talk Science based on an image by ser_igor via iStockphoto). When the battery is charging, the lithium ions flow from the cathode to the anode, and the electrons move from the anode to the cathode.
Here is the full reaction (left to right = discharging, right to left = charging): LiC 6 + CoO 2 ⇄ C 6 + LiCoO 2 How does recharging a lithium-ion battery work? When the lithium-ion battery in your mobile phone is powering it, positively charged lithium ions (Li+) move from the negative anode to the positive cathode.
The charging and discharging of lithium ion battery is actually the reciprocating motion process of lithium ions and electrons. When charging, apply power to the battery to let lithium ions and electrons go to the graphite layer along different paths. At this time, lithium atoms It is very unstable.
Simply storing lithium-ion batteries in the charged state also reduces their capacity (the amount of cyclable Li+) and increases the cell resistance (primarily due to the continuous growth of the solid electrolyte interface on the anode).
Lithium batteries are one of the best rechargeable batteries that can be used repeatedly. It has a wide range of applications, such as mobile phone batteries, power banks, and electric vehicle batteries. etc. So, how does the charging and discharging of lithium ion battery works?
There are three main types of high rate batteries; sealed lead-acid Battery (SLA), high rate lifepo4 battery, and high discharge NMC lithium battery (ternary lithium battery).
The influence on battery from high charge and discharge rates are analyzed. High discharge rate behaves impact on both electrodes while charge mainly on anode. To date, the widespread utilization of lithium-ion batteries (LIBs) has created a pressing demand for fast-charging and high-power supply capabilities.
There was an immediate voltage change when the high rate pulses were applied. The maximum current that could be applied to the cathodes, at the rated charging voltage limit for the cells, was around 10 C. For the anodes, the limit was 3–5 C, before the voltage went negative of the lithium metal counter electrode.
Consequently, this study will contribute to providing solutions for enhancing battery safety and reliability under extreme operating conditions and environments. 1. Introduction According to multiple news sources, the number of electric vehicles (EVs) equipped with lithium-ion batteries (LIBs) in China has recently exceeded 20 million .
Electrolyte is an important factor that can affect the rate performance of LIBs. The electrolytes in LIBs consist of at least one type of lithium salts and one non-aqueous solvent, which produce different conductivities depending on the type of the salts and their interaction with the solvents.
For high rate charging at the cathode, there is a risk of forming a higher resistance phase around the predominantly hexagonal or rhombohedral phase particles . A high rate charge pulse can lower the surface lithium concentration to the point at which irreversible phase change can occur.
In general, high-rate charging and discharging can accelerate the degradation of lithium-ion cells by increasing the loss of active materials, such as lithium inventory and electrolyte (Zhang et al., 2022a, Qu et al., 2022, Bryden et al., 2018, Chen et al., 2024, Yang et al., 2019b, Darma et al., 2016).
Blade battery is a new type of battery based on lithium iron phosphate (LFP) chemical system. What makes it unique is its "blade"-shaped battery cell design.
The blade battery was officially launched by BYD in 2020. BYD claims that compared with ternary lithium batteries and traditional lithium iron phosphate batteries, the blade battery holds advantages in safety, range, longevity, strength and power.
BYD battery subsidiary FinDreams will launch a second generation version of its blade battery later this year, possibly in August. One of the key upgrades in the new battery will be the energy density which is expected to reach 190 Wh/kg.
At an online launch event themed “The Blade Battery – Unsheathed to Safeguard the World”, Wang Chuanfu, BYD Chairman and President, said that the Blade Battery reflects BYD's determination to resolve issues in battery safety while also redefining safety standards for the entire industry.
The Blade battery, which was first introduced in 2020, is an in-house development by BYD. The name refers to the unusual format: the cells are very long and therefore resemble a sword blade. The elongated cells are installed in the battery packs at right angles to the direction of travel.
"In terms of battery safety and energy density, BYD's Blade Battery has obvious advantages," said Professor Ouyang Minggao, Member of the Chinese Academy of Sciences and Professor at Tsinghua University. The Blade Battery has been developed by BYD over the past several years.
The energy efficiency of BYD Blade batteries is so high that it allows the company to produce NEVs with some of the industry's longest ranges. The company's efforts in the development of battery technology over the last 27 years have truly paid off. Despite the nail penetrating the battery, the temperature remained under control. Image: BYD
The lithium iron phosphate battery (LiFePO 4 battery) or LFP battery (lithium ferrophosphate) is a type of using (LiFePO 4) as the material, and a with a metallic backing as the. Because of their low cost, high safety, low toxicity, long cycle life and other factors, LFP batteries are finding a number o.
The lithium iron phosphate cathode battery is similar to the lithium nickel cobalt aluminum oxide (LiNiCoAlO 2) battery; however it is safer. LFO stands for Lithium Iron Phosphate is widely used in automotive and other areas .
Phosphorus has aroused growing concern as a promising anode material for both lithium and sodium ion batteries, owning to its high theoretical capacity and appropriately low redox potential.
Herein, we proposed a new preparation of lithium phosphate (Li 3 PO 4) as a solid electrolyte from lithium mother liquor (Li 2 CO 3) and the phosphate source trisodium phosphate dodecahydrate (Na 3 PO 4 *12H 2 O) for solid-state batteries.
Author to whom correspondence should be addressed. Due to its high thermal stability, environmental friendliness, and safety, lithium phosphate (Li 3 PO 4) is used as a solid electrolyte in battery applications, but it is usually used with dopants due to its lower ionic conductivity, which is required for ion transport.
Lithium iron phosphate modules, each 700 Ah, 3.25 V. Two modules are wired in parallel to create a single 3.25 V 1400 Ah battery pack with a capacity of 4.55 kWh. Volumetric energy density = 220 Wh / L (790 kJ/L) Gravimetric energy density > 90 Wh/kg (> 320 J/g). Up to 160 Wh/kg (580 J/g).
Multiple lithium iron phosphate modules are wired in series and parallel to create a 2800 Ah 52 V battery module. Total battery capacity is 145.6 kWh. Note the large, solid tinned copper busbar connecting the modules together. This busbar is rated for 700 amps DC to accommodate the high currents generated in this 48 volt DC system.
BYD: Vertically integrated battery and EV manufacturer with top market share in both segmentsArcadium Lithium: New lithium major following the merger between Allkem and LiventAlbemarle: Global lithium producer with ambitious expansion plansLG Energy Solutions: Critical battery supplier for ex-China automakers.
Nexeon is an electronics company that develops and manufactures lithium-ion batteries to reduce carbon anode energy inefficiency. Amprius develops an anode out of silicon nanowires for lithium-ion batteries. Natron Energy is an early-stage start up company based in the San Francisco Bay Area.
Lithium batteries are becoming more important as the world moves toward electrification and the need for energy storage grows. Because of this, the demand for lithium batteries is increasing very quickly. As a result, companies that make lithium batteries are expanding their operations all over the world.
In 2022, the global production of lithium-ion batteries was over 2,000 GWh. This number is expected to grow by 33% each year, reaching more than 6,300 GWh by 2026. At the same time, Asia produced 84% of the world's lithium batteries in 2022, making it the leader in production. This trend is expected to continue for the next few years.
Because of this, the demand for lithium batteries is increasing very quickly. As a result, companies that make lithium batteries are expanding their operations all over the world. In 2022, the global production of lithium-ion batteries was over 2,000 GWh. This number is expected to grow by 33% each year, reaching more than 6,300 GWh by 2026.
In 1999, LG Chem made Korea's first lithium-ion battery. Later, in the 2000s, it supplied batteries for the General Motors Volt. After that, the company became a key supplier for many global car brands, such as Ford, Chrysler, Audi, Renault, Volvo, Jaguar, Porsche, Tesla, and SAIC Motor.
However, the industry is mired with trade-offs, with improvement in one domain coming with compromises in another. When it comes to the good old lithium-ion batteries, their gravimetric and volumetric energy density can be, and in fact, has been, improved by the use of anode materials like silicon.
The Green BMS Android app is available here: Green-BMS App Step by step instructions for make Green BMS are available here: https://hackaday.io/project/181453/instructions.
If you are looking to build safe-high performance battery packs, then you are going to need to know how to choose a BMS for lithium batteries. The primary job of a BMS is to prevent overloading the battery cells. So, for this to be effective, the maximum rating on the BMS should be greater than the maximum amperage rating of the battery.
Overcharging can cause swelling, overheating, or even explosions, while deep discharges can permanently degrade the battery. A BMS ensures: Controlled charging and discharging. Voltage and current stabilization. Cell balancing to maintain uniform voltage across cells. Protection against overvoltage, undervoltage, and short circuits.
Smart BMS is an Open Source Battery Management System for Lithium Cells (Lifepo4, Li-ion, NCM, etc.) Battery Pack. The main functions of BMS are: Smart BMS consists of four main components:
A Battery Management Unit (BMU) is a critical component of a BMS circuit responsible for monitoring and managing individual cell voltages and states of charge within a Li-ion battery pack. The BMU collects real-time data on each cell's voltage and state of charge, providing essential information for overall battery health and performance.
Use a BMS with an alternator port with built-in current limiting, such as the Smart BMS CL 12/100 or the Smart BMS 12/200. For more information on charging lithium batteries with an alternator, see the Alternator lithium charging blog and video. Alternator charging 3.5. Battery monitoring
The charging process reaches completion upon attaining the designated voltage of 4.2 Volts. Overall, I would recommend utilizing this circuit. Additionally, the circuit can also balance batteries independently of the charging unit. Hope you will like this guide for designing the BMS circuit diagram for Li-ion battery charging.
For winter storage, disconnect the batteries, charge them to 50%, and store them in a dry, well-ventilated place. Don't let them get below -15°F (-26°C).
By following the right storage practices, you'll be ensuring your battery lasts longer, and your devices keep running smoothly for years to come. The first rule of battery storage is simple—never store a lithium-ion battery in an environment that's too hot or too cold. These batteries work best in moderate, room-temperature environments.
Regular maintenance and safety checks are important to ensure a safe environment for storing and handling lithium-ion batteries. This isn't a one-off task but an ongoing commitment, so scheduling regular inspections of your storage solutions is key. It's also important to keep an eye on the batteries themselves.
Follow guidelines for cleaning, disconnecting, and choosing the right storage location to safeguard your batteries. Monitoring and maintenance during winter storage are crucial for preserving lithium batteries. Regular inspection, temperature monitoring, and maintenance charging help ensure optimal battery health and performance.
The UK doesn't have specific regulations or legislation for the general storage of lithium-ion batteries. The Health and Safety Executive has, however, published guidance on good practices for handling and storing batteries, even though it is not compulsory. Regulations are not prescriptive but instead follow the typical routes:
Lithium-ion battery fires can even reignite after being contained. In this post, we'll talk through the safe storage requirements for lithium-ion batteries that manage the risks to keep people and facilities safe. The UK doesn't have specific regulations or legislation for the general storage of lithium-ion batteries.
Handle with Care: When handling the batteries, be mindful of their fragility and avoid dropping or mishandling them. Lithium batteries are sensitive to physical impact, and any damage to the battery casing can compromise their integrity and safety. 7.