What is a Battery Management System?

 

The power output depends on the battery, and thebattery management system (BMS)is the core of it. It is a system for monitoring and managing the battery. It controls the charge and discharge of the battery by collecting and calculating parameters such as voltage, current, temperature, and SOC. The process, the management system that realizes the protection of the battery and improves the overall performance of the battery is an important link between the battery and the battery application equipment.

The better BMS of foreign companies include UMC, Continental, Delphi, AVL, and FEV, etc. Now they basically follow the AUTOSAR architecture and ISO26262 functional safety requirements, with more software functions, higher reliability, and accuracy. Many domestic battery factories also have self-developed BMS products and applications, includingGrepow battery manufacturer. With the rapid development of batteries and BMS technology, they have become one of the world’s largest battery manufacturers.

BMS mainly includes three parts: hardware, bottom layer software, and application layer software.

The hardware of the battery management system (BMS)

1. Architecture

The topology of Battery Management System(BMS) hardware is divided into two types: centralized and distributed.

(1) The centralized type

The centralized type is to concentrate all the electrical components into a large board, the sampling chip channel utilization is the highest and the daisy chain communication can be adopted between the sampling chip and the main chip, the circuit design is relatively simple, the product cost is greatly reduced, but All the collection wiring harnesses will be connected to the mainboard, which poses a greater challenge to the security of the BMS, and there may also be problems in the stability of the daisy chain communication. It is more suitable for occasions where the battery pack capacity is relatively small and the module and battery pack types are relatively fixed.

(2) The Distributed type

Distributed includes a mainboard and a slave board. It is possible that a battery module is equipped with a slave board. The disadvantage of this design is that if the number of battery modules is less than 12, the sampling channel will be wasted (generally there are 12 sampling chips. Channel), or 2-3 slave boards to collect all battery modules. This structure has multiple sampling chips in one slave board. The advantages are high channel utilization, cost-saving, flexibility in system configuration, and adaptation to different capacities. Modules and battery packs of different specifications and types.

2. Function

The hardware design and specific selection should be combined with the functional requirements of the vehicle and battery system. The general functions mainly include collection functions (such as voltage, current, and temperature collection), charging port detection (CC and CC2), and charging wake-up (CP and A+) ), relay control and status diagnosis, insulation detection, high voltage interlock, collision detection, CAN communication and data storage requirements.

(1) Main controller

Process the information reported from the controller and the high-voltage controller, and at the same time judge and control the battery operating status according to the reported information, realize the BMS-related control strategy, and make the corresponding fault diagnosis and processing.

(2) High voltage controller

Collect and report the total voltage and current information of the battery in real-time, and realize timely integration through its hardware circuit, and provide accurate data for the calculation of the state of charge (SOC) and the state of health (SOH) for the motherboard. Charge detection and insulation detection function.

(3) Slave controller

Real-time collection and reporting of battery cell voltage and temperature information, feedback of the SOH and SOC of each string of cells, and a passive equalization function, effectively ensuring the consistency of cells during power use.

(4) Sampling control harness

Provide hardware support for battery information collection and information interaction between controllers, and at the same time add redundant insurance function to each voltage sampling line, effectively avoid battery short circuit caused by wiring harness or management system.

3. Communication method

There are two ways to transfer information between the sampling chip and the main chip: CAN communication and daisy chain communication. CAN communication is the most stable. However, due to the high cost of power chips and isolation circuits, daisy chain communication is actually SPI communication. The cost is very low, and the stability is relatively poor. However, as the pressure on cost control is increasing, many manufacturers are shifting to the daisy chain mode. Generally, two or more daisy chains are used to enhance communication stability.

4. Structure

BMS(Battery Management System) hardware includes power supply IC, CPU, sampling IC, high-drive IC, other IC components, isolation transformer, RTC, EEPROM, CAN module, etc. The CPU is the core component, and the functions of different models are different, and the configuration of the AUTOSAR architecture is also different. Sampling IC manufacturers mainly include Linear Technology, Maxim, Texas Instruments, etc., including collecting cell voltage, module temperature, and peripheral configuration equalization circuits.

Bottom layer software

According to the AUTOSAR architecture, it is divided into many general functional modules, which reduces the dependence on hardware, and can realize the configuration of different hardware, while the application layer software changes little. The application layer and the bottom layer need to determine the RTE interface, and consider the flexibility of DEM (fault diagnosis event management), DCM (fault diagnosis communication management), FIM (function information management), and CAN communication reserved interfaces, which are configured by the application layer.

Application layer software of the BMS

The software architecture mainly includes high and low voltage management, charging management, state estimation, balance control, and fault management, etc.

1. High and low voltage management

Generally, when the power is on normally, the VCU will wake up theBMSthrough the hardwire or 12V of the CAN signal. After the BMS completes the self-check and enters the standby mode, the VCU sends the high-voltage command, and the BMS controls the closed relay to complete the high-voltage. When the power is off, the VCU sends a high-voltage command and then disconnects and wakes up 12V. It can be awakened by CP or A+ signal when the gun is plugged in in the power-off state.

2. Charging management

(1) Slow charge

Slow charging uses an AC charging station (or 220V power supply) to convert AC to DC to charge the battery through an on-board charger. The charging station specifications are generally 16A, 32A, and 64A, and it can also be charged through a household power supply. The BMS can be awakened by CC or CP signal, but it should be ensured that it can sleep normally after charging. The AC charging process is relatively simple, and it can be developed in accordance with the detailed regulations of the national standard.

(2) Fast charge

Fast charging is to charge the battery with DC output from the DC charging pile, which can achieve 1C or even higher rate charging. Generally, 80% of the power can be charged in 45 minutes. Wake up by the auxiliary power A+ signal of the charging pile, the fast charging process in the national standard is more complicated, and there are two versions of 2011 and 2015 at the same time, and the different understanding of the technical details of the charging pile manufacturer’s unclear technical details of the national standard process also causes the vehicle charging adaptability A great challenge, so fast charging adaptability is a key indicator to measure the performance of BMS products.

3. Estimation function

(1) the State Of Power

SOP (State Of Power) mainly obtains the available charge and discharge power of the current battery through the temperature and SOC lookup table. The VCU determines how the current vehicle is used according to the transmitted power value. It is necessary to consider both the ability to release the battery and the protection of the battery performance, such as a partial power limit before reaching the cut-off voltage. Of course, this will have a certain impact on the driving experience of the whole vehicle.

(2) state of health

SOH (state of health) mainly characterizes the current state of health of the battery, which is a value between 0-100%. It is generally believed that the battery can no longer be used after it is lower than 80%. It can be expressed by the change of battery capacity or internal resistance. When using the capacity, the actual capacity of the current battery is estimated through the battery operating process data, and the ratio of the rated capacity to the rated capacity is the SOH. Accurate SOH will improve the estimation accuracy of other modules when the battery decays.

(3) the State Of Charge

SOC (State Of Charge) belongs to the BMS core control algorithm, which characterizes the current remaining capacity state, mainly through the ampere-hour integration method and EKF (Extended Kalman Filter) algorithm, combined with correction strategies (such as open-circuit voltage correction, full charge correction, charging End correction, capacity correction under different temperatures and SOH, etc.). The ampere-hour integration method is relatively reliable under the condition of ensuring the accuracy of current acquisition, but the robustness is not strong. Because of the error accumulation, it must be combined with a correction strategy. The EKF has strong robustness, but the algorithm is more complex and difficult to implement. Domestic mainstream manufacturers generally can achieve accuracy within 6% at room temperature, and it is difficult to estimate high and low temperatures and battery attenuation.

(4) the State Of Energy

SOE (State Of Energy) algorithm manufacturers do not develop much now or use a simpler algorithm, look up the table to get the ratio of the remaining energy to the maximum available energy in the current state. This function is mainly used to estimate the remaining cruising range.

4. Fault diagnosis

According to the different performance of the battery, it is divided into different fault levels, and in the case of different fault levels, the BMS and VCU will take different treatment measures, warning, limiting power, or directly cutting off the high voltage. Failures include data collection and rationality failures, electrical failures (sensors and actuators), communication failures, and battery status failures.

5. Balance control

The equalization function is to eliminate the inconsistency of the battery cells generated during battery use. According to the shortboard effect of the barrel, the cells with the worst performance during charging and discharging first reach the cut-off condition, and the other cells have some capabilities. It is not released, causing battery waste.

Equalization includes active equalization and passive equalization. Active equalization is the transfer of energy from more monomers to fewer monomers, which will not cause energy loss, but the structure is complex, the cost is high, and the requirements for electrical components are relatively high. Relatively passive The balance structure is simple and the cost is much lower, but the energy will be dissipated and wasted in the form of heat. Generally, the maximum balance current is about 100mA. Now many manufacturers can achieve better balance effects using passive balance.

The BMS(Battery Management System) control method, as the central control idea of ​​the battery, directly affects the service life of the battery, the safe operation of the electric vehicle, and the performance of the entire vehicle. It has a significant impact on battery life and determines the future of new energy vehicles. A good battery management system will greatly promote the development of new energy vehicles.

If you are interested in battery with BMS, please don’t hesitate to contact us!
Email:info@grepow.com
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Tips to Start a Car in Cold Weather

 There are many things to pay attention to when driving in winter, such as warming up before driving in winter. However, it is difficult for many cars to start in winter, which makes it difficult for many drivers. So, what is going on if a taxi fails to start in winter? How to solve the problem of not being able to catch a car in winter? The following is an introduction to the reasons and solutions for the car not catching fire in winter.

Table of Contents

• Why Can’t the Car Start in Cold Weather?
  • 1. The battery is aging or dead
  • 2. The ignition system is malfunctioning
  • 3. The exhaust pipe freezes
  • 4. Other
• What to Do If Your Car Won’t Start in the Cold?
  • 1. Check the battery status
• 2. Change the proper oil
  • 3. Replace the spark plug in time

Why Can’t the Car Start in Cold Weather?

1. The battery is aging or dead

For the engine to run normally, several conditions must be met at the same time: fuel, air, and starting energy.
The most important thing is the starting energy. It is because the spark plug must have the energy to jump the starter, and the starter must also have the energy to run to drive the engine to do work, and their energy is electricity.
Therefore, we often encounter the failure of the car to jump the starter normally. In most cases, it is caused by the lack of electricity, that is, the battery is running out of power.
If the battery is not used for a long time, it will discharge by itself. If it is too long, the battery will be dead. Also, after the car engine stops working, which is what we call the flameout, avoid using in-car electrical appliances. Without the power supply of the engine, long-term use of electrical appliances such as car audio equipment or car headlights will consume the internal power of the battery.

2. The ignition system is malfunctioning

Due to the low intake air temperature in the cylinder, the fuel atomization in the cylinder is not good. If there is insufficient ignition energy, it is easy to cause cylinder flooding, and too much fuel will accumulate in the cylinder, exceeding the ignition limit concentration and unable to start the car.
The fire limit concentration is a range, but it is not a value. It can only start within this range, and it will not work if it is high or low.
If this problem occurs, you can check whether there are any oil stains between the spark plug electrodes. If it is cleaned and installed, it can start. The thorough method is to check the ignition system to eliminate the reasons for low ignition energy, such as spark plug electrode gap, ignition coil energy, high-voltage line status, etc.

3. The exhaust pipe freezes

This situation is more likely to happen in winter when the weather is relatively cold and the temperature is relatively low.
Those car owners whose home and work are relatively close, their cars are used less frequently, the water vapor produced by the combustion of the engine freezes on certain parts of the exhaust pipe, and the heat of short-distance driving is not enough to melt the ice. After one night, more ice has formed, and the cycle time will affect the starting and exhaust of the vehicle. Therefore, the car should not be driven, and should not be left in the corner all the time.

4. Other

In addition, the reason for the failure to start in winter may also be the addition of water or low-quality antifreeze, which caused the waterway to be frozen and even the engine was frozen and cracked, and the car’s water pump could not work and could not start.

What to Do If Your Car Won’t Start in the Cold?

1. Check the battery status

In general, the difficulty of starting a car in winter is mostly caused by battery power loss or expiration of battery life. When the battery power is insufficient, the speed is weak when starting the car, and only a click sound is heard, and the click sound will gradually become a click sound when the fire starts again. Avoid continuous ignition to avoid exhaustion of the battery.
Do not park the vehicle for a long time in winter. Generally, the vehicle should be driven out for a full circle after parking for a week, so that the battery power can be effectively replenished.
The nominal service life of the battery is generally 2-3 years, and the maintenance-free battery generally has to be replaced in 2-3 years, and the water-filled battery can even be used for 6-7 years under good maintenance. Frequently check the electrolyte capacity of the water-filled battery If the battery does not leak but the electrolyte is lacking, please replenish distilled water in time.
Of course, in this case, you can also use a jump starter. Now the jump starter can not only start the car, it is convenient to carry, but also has many auxiliary functions. For example, the jump starter produced by Grepow can not only jump starter 3.0L ~ 9.0L diesel vehicles and gas vehicles, but also Air INFLATOR, LED, multiple sockets (which can charge your mobile phones, Bluetooth headsets, etc.), and also have wireless charging functions, etc. Customized services are also provided.

2. Change the proper oil

In winter, as the temperature drops, the viscosity of the oil will increase, and the oil will flow difficultly, which will increase the resistance of the engine.
If it is difficult to start, please check whether the oil label is wrong.
Engine oil marking includes two parts: classification and viscosity specification. At present, most of the engine oils on the market use SAE and other grades to mark the viscosity. SAE is the abbreviation of “American Society of Automotive Engineers” in English. For example, in 5W-40, “W” means Winter, which refers to the low-temperature viscosity grade of the oil. The smaller the number in front of it, the better the low-temperature fluidity of the oil, and the lower the ambient temperature available for use. The better the protection of the engine during cold start. The number after the “-” sign is the high-temperature viscosity grade of the lubricating oil. The larger the number, the greater the viscosity and the higher the applicable maximum temperature.
If you originally used 5W-40 oil, you can consider switching to 5W-30 or 0W-40 oil in winter to reduce the oil viscosity and make it easier to start

3. Replace the spark plug in time

After several years of use, spark plugs are likely to cause problems such as carbon deposits, leakage, excessive gaps, and ablation, which will cause difficulties in the car ignition. Cold start and even hot engine start are difficult and often require multiple ignitions. Therefore, please check the status of the spark plug and replace it in time if you drive to a certain number of kilometers or if you feel that the vehicle is difficult to start, drive weak, jitter, increase fuel consumption, or inexplicably stalled.

What do you think you need to prepare for driving in winter? If you need a portable jump starter, please contact us as soon as possible!
Email: info@grepow.com
jump starter: https://www.grepow.com/page/jump-starter.html

the lithium battery charging process

 

Lithium-ion batteries generally use lithium alloy metal oxide as the positive electrode material, graphite as the negative electrode material, and the non-aqueous electrolyte. Almost all mobile phones we use are lithium batteries. At present, most of the popular electric vehicles on the market are powered bylithium iron phosphate batteries. How do the lithium batteries charge and discharge?

First, let’s take a look at the structure of lithium batteries. Lithium batteries are generally composed of a positive electrode, negative electrode, electrolyte, and separator. Our common mobile phone lithium batteries are square in daily life. The batteries in electric vehicle battery packs are generally round. There are laminated and winding types. In addition to the positive and negative electrodes of the four contacts on a common mobile phone battery, the remaining contacts are simply used to detect (or monitor) various information of the mobile phone battery.

The positive electrode of lithium battery is generally lithium manganese oxide or lithium cobalt oxide, and lithium nickel cobalt manganese oxide materials. Electric bicycles generally use lithium nickel cobalt manganese oxide (commonly known as ternary) or ternary + a small amount of lithium manganate; the negative electrode is generally active The material is graphite or carbon with a similar graphite structure. The separator between the positive electrode and the negative electrode is a specially formed polymer film with a pore size that satisfies good ion permeability and also has electronic insulation, which allows lithium ions to pass freely. And electrons cannot pass. The electrolyte plays a role in transporting charges between the positive and negative electrodes. Generally, it is a carbonate-based solvent in which lithium hexafluorophosphate is dissolved, and a gel electrolyte is used for polymers.

When alithium batteryis charged, the positive electrode releases lithium ions, and the lithium ions pass through the diaphragm through the electrolyte, move to the negative electrode, and combine with the electrons of the abdominal muscles. At this time, the chemical reaction of the positive electrode is LiCoO2=Li(1-x)CoO2 +xLi++xe- (electron), the chemical reaction on the negative electrode is 6C+xLi++xe- = LixC6. When a lithium battery is discharged, the movement of lithium ions is exactly the opposite. Lithium ions enter the electrolyte from the negative electrode, pass through the diaphragm and finally reach the positive electrode, while the electrons travel from the negative electrode to the positive electrode by the external circuit (the direction of electron movement is opposite to the current direction), and the positive electrode This process can make the lithium battery output electric energy.

The charging process of lithium batteries is generally divided into three stages: trickle charging, constant current charging, and constant voltage charging. Take a mobile phone battery as an example. When charging starts, the internal charging management chip first detects the voltage of the battery to be charged. If the voltage is lower than 3V, pre-charge is required. The charging current is 1/10 of the set current and the voltage rises to 3V. , Into the standard charging process. The standard charging process is constant current charging with the set current, when the battery voltage rises to 4.20V, change to constant voltage charging, and keep the charging voltage at 4.20V. At this time, the charging current gradually decreases, and when the current drops to 1/10 of the set charging current, charging ends. Generally, the output voltage of a mobile phone charger is 5V, and the charging management chip inside the mobile phone is responsible for reducing the voltage to 3.7V suitable for the mobile phone battery.

Lithium batteries have relatively high energy. It has a high storage energy density, reaching 460-600Wh/kg, which is about 6-7 times that of lead-acid batteries; long service life, generally up to six years; high power endurance; low self-discharge rate. The applications in daily life are becoming wider and wider.

High-voltage Lithium Batteries Development

 

A high-voltage battery refers to a battery whose battery voltage is relatively higher than the ordinary battery that we use. With the development of global diversification, our lives are constantly changing, including the various electronic products we come into know. Then you must not know some of the components of these products, such as high-voltage lithium-ion batteries.

With the continuous improvement of the requirements for the capacity of lithium-ion batteries by electrical equipment, people have higher and higher expectations for the improvement of the energy density of lithium-ion batteries. In particular, various portable devices such as smart-phones, tablet computers, and notebook computers have put forward higher requirements for lithium-ion batteries with small size and long standby time. Also in other electrical equipment, such as energy storage equipment, power tools, electric vehicles, etc., are constantly developing lithium-ion batteries with lighter weight, smaller size, higher output voltage, and power density, so the development of high energy density Lithium-ion batteries are an important research and development direction in the lithium battery industry.

A high-voltage battery refers to a battery whose battery voltage is relatively higher than the ordinary battery. According to battery cells and battery packs, it can be divided into two types. The high-voltage battery is defined from the voltage of the battery cell. This aspect is mainly for lithium batteries. At present, the types of lithium battery cells mainly include high-voltage lithium battery cells and low-voltage lithium battery cells.

At present, lithium cobalt oxide has been widely studied and applied as a high-voltage anode material. The structure is non-nafeo2 type, which is more suitable for lithium-ion insertion and ejection. The theoretical energy density of lithium cobalt oxide is 274mAh/g, the production process is simple, the electrochemical performance is stable, and the market occupancy is high. In practical applications, only part of lithium ions can be reversibly inserted and ejected. The actual energy density is about 167mAh/g (working voltage is 4.35v). Increasing the working voltage can significantly increase the energy density. For example, increasing the operating voltage from 4.2v to 4.35v can increase the energy density by about 16%.

High-voltage lithium battery cells have higher energy density and lower safety performance than low-voltage batteries, but their discharge platform is relatively high. Under the same capacity, high-voltage batteries are lighter than low-voltage batteries in terms of volume and weight.

With the increase in voltage, high-voltage lithium-ion batteries will reduce certain safety performance during use, so they have not been used in batches in power vehicles. At present, the battery cathode materials used in power vehicles are mainly ternary materials and lithium iron phosphate. To increase the energy density to meet the demand, generally choose 811NCM and NCA and other high nickel cathode materials, high capacity silicon-carbon anode or improve battery space utilization and other methods to improve its energy density and endurance.

High current and high voltage make lithium cobalt oxide materials used in high-energy-density batteries, such as high-end mobile phone battery manufacturers’ increasingly high battery performance requirements, which are mainly reflected in the demand for higher energy density, such as carbon requirements for 4.35V battery cathodes The energy density is about 660wh/L, and the 4.4V battery has reached about 740wh/L. This requires the anode material to have a higher compaction density, a higher empty volume, and the structure of the material under high pressure and high pressure has a better stability. However, lithium cobalt oxide electrode materials have shortcomings such as scarcity of cobalt resources, high prices, and certain toxicity of cobalt ions, which limit its wide application in power lithium batteries.

In terms of discharge rate of high-voltage and low-voltage batteries, high-voltage lithium batteries have a higher discharge rate and stronger power than low-voltage lithium batteries. Therefore, in theory, a high-voltage battery should be more suitable for use in products and equipment that require high-rate discharge. , In order to better exert its advantages.

In the process of research and design, there must be problems of one kind or another. This requires our scientific research workers to constantly sum up the experience in the design process in order to promote continuous product innovation.

If you want to know more about high-voltage batteries, please check https://www.grepow.com/page/high-voltage-battery.html

For customized high voltage batteries, please contact us directly at info@grepow.com

LiFePO4 batteries are used in the industrial

 

Lithium iron phosphate battery is a lithium-ion battery that uses lithium iron phosphate (LiFePO4) as the positive electrode material and carbon as the negative electrode material. The rated voltage of the monomer is 3.2V, and the charge cut-off voltage is 3.6V~3.65V.

Application of lithium iron phosphate (LiFePO4) battery

1.Application of the new energy automobile industry

Lithium iron phosphate batteries are widely used in passenger cars, buses, logistics vehicles, low-speed electric vehicles, etc. due to their safety and low-cost advantages. Although, in the current new energy passenger vehicle field, it is subject to the state’s subsidy policy for new energy vehicles. Influence, relying on the advantages of energy density, ternary batteries occupy a dominant position, but lithium iron phosphate batteries still occupy an irreplaceable advantage in fields such as passenger cars and logistics vehicles. In the field of passenger cars, lithium iron phosphate batteries remain mainstream. In the field of special-purpose vehicles, the proportion of lithium iron phosphate batteries is gradually increasing. The use of lithium iron phosphate batteries in the extended-range electric vehicle market can not only improve the safety of vehicles, but also support the marketization of extended-range electric vehicles, eliminating the anxiety of pure electric vehicles such as mileage, safety, price, charging, and subsequent battery issues.

2. Start the application on the power supply

In addition to the power lithium battery characteristics, the starter lithium iron phosphate battery also has the ability of instantaneous high-power output. The traditional lead-acid battery is replaced by a powerful lithium battery with an energy of less than one kilowatt-hour, and the traditional starter motor and generator are replaced by a BSG motor. , It not only has the function of start and stop at idle speed, but also has the functions of engine stop coasting, coasting and braking energy recovery, acceleration assist, and electric cruise.

3. Application of energy storage market

Lithium iron phosphate battery has a series of unique advantages such as high working voltage, high energy density, long cycle life, low self-discharge rate, no memory effect, and green environmental protection. It also supports stepless expansion and is suitable for large-scale electric energy storage. Energy power stations have good application prospects in such fields as safe grid connection, grid peak shaving, distributed power stations, UPS power supplies, and emergency power systems.

With the rise of the energy storage market, in recent years, some power battery companies have deployed energy storage business to open up new application markets for lithium iron phosphate batteries. On the one hand, due to the characteristics of ultra-long life, safe use, large capacity, and environmental protection, lithium iron phosphate can be transferred to the energy storage field, which will extend the value chain and promote the establishment of new business models. On the other hand, energy storage systems supporting lithium iron phosphate batteries have become a mainstream choice in the market. According to reports, lithium iron phosphate batteries have tried to be used in electric buses, electric trucks, user-side, and grid-side frequency modulation.

1) Safe grid connection of renewable energy power generation

The inherent randomness, intermittent news, and volatility of wind power generation determine that its large-scale development will inevitably have a significant impact on the safe operation of the power system. With the rapid development of the wind power industry, especially most wind farms in my country are “large-scale centralized development and long-distance transmission”, the grid-connected power generation of large-scale wind farms pose severe challenges to the operation and control of large-scale power grids.

Photovoltaic power generation is affected by ambient temperature, sunlight intensity, and weather conditions, and photovoltaic power generation has the characteristics of random fluctuations. my country presents a development trend of “decentralized development, low-voltage on-site access” and “large-scale development, medium, and high voltage access” simultaneously, which puts forward higher requirements for power grid peak shaving and safe operation of the power system.

Therefore, large-capacity energy storage products have become a key factor in solving the contradiction between the power grid and renewable energy power generation. The lithium iron phosphate battery energy storage system has the characteristics of fast working condition conversion, flexible operation mode, high efficiency, safety, and environmental protection, and strong scalability. Engineering applications have been carried out in the national wind and solar storage and transmission demonstration project, which will effectively improve equipment efficiency and solve Local voltage control problems, improve the reliability of renewable energy power generation and improve power quality so that renewable energy can become a continuous and stable power supply.

With the continuous expansion of capacity and scale and the continuous maturity of integrated technology, the cost of energy storage systems will be further reduced. After long-term safety and reliability tests, lithium iron phosphate battery energy storage systems are expected to be used in wind power, photovoltaic power generation, etc. Safe grid connection of energy power generation and improvement of power quality are widely used.

2) Lithium iron phosphate battery for grid peak shaving

The main method of power grid peak shaving has always been pumped storage power stations. As the pumped storage power station needs to build two reservoirs, the upper and lower reservoirs are restricted by geographical conditions, it is not easy to construct in plain areas, and it covers a large area and high maintenance cost. Use lithium iron phosphate battery energy storage system to replace pumped storage power station, cope with grid peak load, free of geographical conditions, freedom of location, less investment, less land occupation, low maintenance cost, and will play an important role in the process of power grid peak regulation.

3) Lithium iron phosphate battery for distributed power station

The shortcomings of large-scale power grids make it difficult to guarantee the quality, efficiency, safety, and reliability requirements of the power supply. For important units and enterprises, dual power supplies or even multiple power supplies are often required as backup and protection. Lithium iron phosphate battery energy storage system can reduce or avoid power outages caused by grid failures and various accidents, and ensure a safe and reliable power supply for hospitals, banks, command and control centers, data processing centers, chemical materials industries, and precision manufacturing industries. Play an important role.

4) Lithium iron phosphate battery for UPS power supply

The sustained and rapid development of China’s economy has brought about the decentralization of UPS power users’ demand, which has caused more industries and more enterprises to have a continuous demand for UPS power.

Compared with lead-acid batteries, lithium iron phosphate batteries have the advantages of long cycle life, safety and stability, environmental protection, and low self-discharge rate. With the continuous maturity of integration technology, the cost continues to decrease. Lithium iron phosphate batteries are used in UPS power batteries. Will be widely used.

4. Applications in other fields

Lithium iron phosphate battery is also widely used in the military field because of its good cycle life, safety, low-temperature performance, and other advantages. Grepow battery company made a strong appearance at the military-civilian integration technology innovation exhibition, exhibiting military products including -45℃ military ultra-low temperature battery.

If you are interested in our products, please don’t hesitate to contact us at any time!
Email: info@grepow.com
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Wide temperature-range Ni-MH battery -40℃ to 80℃

 

The temperature has one of the greatest impacts on the charge and discharge performance of batteries. The electrode/electrolyte interface is considered the heart of the battery, and the electrochemical reactions at this interface are closely related to the ambient temperature. If the temperature drops, the reaction rate of the electrode also drops.

When NiMH batteries are charged and discharged, multiple factors must be considered: the surrounding environment of the batteries but especially battery performance and service life under extreme temperatures.

We will explore what occurs to NiMH batteries, particularly wide temperature-range NiMH batteries, when under low and high temperatures.

Wide temperature-range NiMH batteries

Wide temperature-range NiMH batteries, as their name implies, are a type of NiMH batteries with a wide working-temperature range and excellent performance at -40°C to 80°C. In other words, these batteries can operate efficiently at both low and high temperatures, and their temperature limitations are greatly reduced.

Under low temperatures

The discharge efficiency of ordinary nickel-hydrogen batteries are significantly reduced at low temperatures. At -20°C, the lye reaches its freezing point and the battery charging speed greatly diminishes. Charging at low temperatures (below 0°C) increases the internal pressure of the battery and possibly causes the safety valve to open.

In order to charge effectively, the ambient temperature range must be controlled between 5℃ to 30℃. Generally, charging efficiency increases with the rise of temperature. However, when the temperature rises above 45℃, the performance of the battery degrades, and the cycle life of the battery greatly shortens.

Under low temperatures, the viscosity of electrolyte becomes higher, the proton transfer rate inside the electrode becomes slower, and the ohmic internal resistance also increases, which leads to larger polarization of the battery during discharge. Some batteries cannot discharge at low temperatures due to large polarization.

Under high temperatures

Under high temperature, the viscosity of the electrolyte decreases, and the hydrophilic ability of various materials increases. Liquid absorption also increases, which leads to the expansion of the electrode sheet, and liquid starts to leak from poor electrical receptivity.

The following is the electrochemical principle of charging and discharging Ni-MH batteries with KOH as the electrolyte (7moL/LKOH+15g/LLiOH).

Charge

Positive Pole: Ni(OH)2+OH-→NiOOH+H2O+e-

Negative Pole: M+H2O+e-→MH+OH-

Total Response: M+Ni(OH)2→MH+NiOOH

Discharge

Positive Pole: NiOOH+H2O+e-→Ni(OH)2+OH-

Negative Pole: MH+OH-→M+H2O+e-

Total Response: MH+NiOOH→M+Ni(OH)2

In the above formula, M is the hydrogen storage alloy and MH is the hydrogen storage alloy with adsorbed hydrogen atoms. The most commonly used hydrogen storage alloy is LaNi5.

Characteristics of a wide temperature-range Ni-MH battery

The following are a couple of the characteristics of a Grepow’s wide temperature-range Ni-MH battery:

The charging and discharging efficiency of 0.2C at -40℃ can reach 80%

The charging and discharging efficiency of 0.2C at 80℃ can reach 85%

Ni-MH battery technology has been tried, tested and proven for commercial and industrial applications especially in automotive batteries and outdoor power supplies in high and cold temperatures. Its safety and reliability are unparalleled in the market.

Grepow Inc. offers a variety of Ni-MH batteries with a wide temperature range. These batteries provide new electrode-development technologies that can achieve a long life, and they have good usability and stability with compatible sizes.

For more information on batteries, stay tuned to our blog or our Battery Monday channel.

If you are interested in our products, don’t hesitate to contact us at any time!

Email: info@grepow.com

Grepow Website: https://www.grepow.com/

the causes of lithium batteries to swell

Lithium-ion polymer batteries are widely used due to their long life and high capacity. However, there are some issues that can arise, such as swelling, unsatisfactory safety performance, and accelerated cycle attenuation.

This article will primarily focus on battery swelling and its causes, which can be divided into two categories: the first is a result of a change in thickness of the electrode, and the other is a result of the gas produced by the oxidation and decomposition of electrolytes.

The change in thickness of the electrode pole piece

When a lithium battery is used, the thickness of the electrode pole pieces, especially the graphite negative electrodes, will change to a certain extent.

Lithium batteries are prone to swelling after high-temperature storage and circulation, and the thickness growth rate is about 6% to 20%. Of this, the expansion rate of the positive electrode is only 4%, the negative electrode’s is more than 20%.

The fundamental reason for the increase in the thickness of the lithium battery pole piece is due to the nature of graphite. The negative electrode graphite forms LiCx (LiC24, LiC12, LiC6, etc.) when lithium is inserted, and the lattice spacing changes, resulting in microscopic internal stress and an expansion of the negative electrode.

[caption id="attachment_3476" align="aligncenter" width="505"] The figure is the schematic diagram of the structure change of the graphite anode plate in the process of placement, charge, and discharge.[/caption]

The expansion of graphite negative electrodes is mainly caused by irreversible expansion after lithium insertion. This part of the expansion is mainly related to the particle size, the adhesive, and the structure of the pole piece. The expansion of the negative electrode causes the core to deform, which in turn causes the following: a cavity between the electrode and the diaphragm, micro-cracks in the negative electrode particles, breaking and reorganizing of the solid electrolyte interface (SEI) membrane, the consummation of electrolytes, and deterioration of the cycle performance.

There are many factors that affect the thickness of the negative pole piece although the properties of the adhesive and the structural parameters of the pole piece are the two most important reasons.

The commonly used bonding agent for graphite negative electrodes is SBR. Different bonding agents have different elastic modulus and mechanical strength and have different effects on the thickness of the pole piece. The rolling force after the pole piece is coated also affects the thickness of the negative pole piece in battery use.

When the amount of SBR added is inconsistent, the pressure on the pole piece during rolling will be different. Different pressures will cause a certain difference in the residual stress generated by the pole piece. The higher the pressure, the greater the residual stress, which leads to physical storage expansion, a full electric state, and an increase in the expansion rate of the empty electric state.

The expansion of the anode leads to the deformation of the coil core, which affects the lithium intercalation degree and Li + diffusion rate of the negative electrode, thus seriously affecting the cycle performance of the battery.

Bloating caused by lithium battery gas production

The gas produced in the battery is another important cause of battery swelling. Dependent on whether the battery is in a normal temperature cycle, high-temperature cycle, or high-temperature shelving, it will produce different degrees of swelling and gas production.

According to the current research results, cell bloating is essentially caused by the decomposition of electrolytes. There are two cases of electrolyte decomposition: one is that there are impurities in the electrolyte, such as moisture and metal impurities, which cause the electrolyte to decompose and produce gas. The other is that the electrochemical window of the electrolyte is too low, which causes decomposition during the charging process.

After a lithium battery is assembled, a small amount of gas is generated during the pre-formation process. These gases are inevitable and are also the source of irreversible capacity loss of the battery.

During the first charging and discharging process, the electrons from the external circuit to the negative electrode react with the electrolyte on the surface of the negative electrode to generate the gas. During this process, the SEI is formed on the surface of the graphite negative electrode. As the thickness of the SEI increases, electrons cannot penetrate and inhibit the continuous oxidation and decomposition of the electrolyte.

When a battery is used, the internal gas production gradually increases due to the presence of impurities in the electrolyte or excessive moisture in the battery. These impurities in the electrolytes need to be carefully removed. Inadequate moisture control may be caused by the electrolyte itself, improper battery packaging, moisture, or damage to the corners. Any overcharge and over-discharge, abuse, and internal short-circuiting will also accelerate the gas production rate of the battery and cause battery failure.

In different systems, the degree of battery swelling is different.

For instance, in the graphite anode system battery, the main causes of gas swelling are the SEI film formation, excessive moisture in the cell, abnormal chemical conversion process, poor packaging, etc.

In the lithium titanate anode system, battery swelling is more serious. In addition to the impurities and moisture in the electrolyte, lithium titanate cannot form an SEI film on its surface like a graphite-anode system battery to inhibit its reaction to the electrolyte.

If you are interested in good quality battery products, please don't hesitate to contact us at any time!
Email: info@grepow.com
Grepow Website: https://www.grepow.com/