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The lithium ion battery design specification includes the design specification of PACK lithium battery summary, some design specifications of lithium battery PACK case, square type lithium battery safety design, specification design of cylindrical lithium ion battery type lithium battery case, safety code for design of standardization, we take a look at these lithium battery design specifications.
First, PACK lithium battery design specifications safety preface.
Because there are hundreds of millions of mobile phones worldwide, to achieve security, the failure rate of security protection must be less than 1/100000000. As a result, the circuit board failure rate is generally higher than 1/100000000. Therefore, the battery system design must have more than two lines of security. The common error design is to use the charger (adaptor) to directly remove the charging pool. In this way, the overcharge protection task is completely delivered to the protective panel on the battery pack. Although the protective plate failure rate is not high, but the failure rate is low, even to one millionth chance on global or every day there will be an explosion accident, we each battery engineer must to the maximum extent to prevent the occurrence of the accident.
Two, PACK lithium battery design specifications, experience summary:
The battery system can provide two safety protection for overcharge, over discharge and over current, and the failure rate of each protection is 1/10000, two protection can reduce the failure rate to 1/100000000. The common battery charging system is shown below. It contains two parts: charger and battery pack.
①The charger includes two parts, the adapter (Adaptor) and the charging controller. The adapter transfers alternating current to direct current, and the charging controller limits the maximum current and maximum voltage of the direct current.
②The battery pack contains two parts of the protective plate and battery core, and a PTC to limit the maximum current. The function of adapter AC DC text block in the following diagram: current limiting of electric controller. Charger text block function: protection plate overcharge, over discharge, over-current and other protection. Storage battery: the limit of the text box. The battery core mobile phone battery system as an example, overcharge protection system using the charger output voltage is set at about 4.2V, to achieve the first layer of protection, so that the failure of the battery protection board, the battery will not be overcharged and dangerous. The second protection is the overcharge protection function of the protection board, which is generally set to 4.3V. In this way, the protection board is usually not responsible for cutting off the charging current, only when the charger voltage is abnormally high, it needs to be operated. Over current protection is the protection plate and limit plate to be responsible, this is the two barrier, preventing overcurrent and external short circuit. Because over discharge will only occur in the process of electronic products being used. Therefore, the general design is provided by the circuit board of the electronic product to provide the first protection, and the protection board on the battery pack provides second protection. When the electronic product detects that the supply voltage is lower than 3.0V, it should be automatically shut down. If the product does not design this function, the protection board will turn off the discharge circuit when the voltage is low to 2.4V.
Experience in the design of lithium batteries: the battery system is designed to provide two electronic protection against overcharge, over discharge, and over current. Remove the protective plate and charge the battery. If the battery explodes, it will mean bad design. Remove the protective plate and charge the battery. If the battery explodes, it will mean bad design. Although the method provides two protection, but because consumers in the charger is broken, often buy non original charger to charge the charger industry, based on cost considerations, the charge controller removed, to reduce costs. As a result, bad money drives out good money, and many bad chargers appear on the market. This makes overcharge protection lose the first and most important line of defense. Overcharge is also the most important factor in battery explosion, so inferior charger can be called the culprit of battery explosion. Of course, not all battery systems use the solution as shown above. In some cases, there is also a charge controller in the battery pack.
The lithium battery design specification example: for example, many notebook computers with battery bars, there is a charge controller. This is because notebook computers typically charge the controller to the computer and only give an adapter to the consumer. Therefore, the extra battery pack of the notebook computer must have a charge controller to ensure the safety of the battery pack when the adapter is charged. In addition, the product that uses the car smoke charger, sometimes also will charge controller to do in the battery group. The last line of Defense: if the protective measures of Electronics fail, the last line of defense will be supplied by the core. The safety level of the electric core can be roughly graded according to whether the core can pass the external short-circuit and overcharge. Because before the battery explodes, if the lithium atoms accumulate inside the material surface, the explosion will be more powerful. Moreover, overcharge protection often has only one line of defense because consumers use inferior chargers. Therefore, the ability to withstand overcharge of the core is more important than the ability to withstand external short-circuit. Aluminum shell and steel shell electric core safety comparison, aluminum shell relative to the steel shell has a high security advantage.
Three, lithium battery design specifications safety design points:
1, in order to avoid excessive battery discharge or overcharge due to improper use, there are three protection mechanisms in the single lithium-ion battery. One is using the switching element, when the battery temperature rises, its resistance increases, when the temperature is too high, it will automatically stop the power supply; the two is to choose the appropriate partition material, when the temperature rises to a certain value, partition of tiny pores will automatically dissolve, and the lithium ion can pass from stop, the internal reaction cell; the three is to set the safety valve (that is at the top of the battery discharge hole), the internal pressure of the battery is increased to a certain value, the safety valve will automatically open, to ensure the safety of battery.
2, the design of battery safety safety is not safe at sometimes, the battery itself although the safety control measures, but for some reason the control failure, the lack of safety valve or safety valve through the gas to release the internal pressure of the battery will rise sharply and explosion.
3, the battery safety design in general, the total energy of lithium ion battery storage and its security is inversely proportional, with the increase of the capacity of the battery, the battery volume increases, the heat transfer performance variation, that will substantially increase the possibility of accidents. For lithium ion batteries for mobile phones, the basic requirement is that the probability of safety accidents is less than one million per cent, which is also the lowest standard acceptable to the public. For large capacity lithium ion battery, especially automobiles and other large capacity lithium ion batteries, are particularly important for forced cooling.
Four, lithium battery safety design measures:
1, choose the safer choice of electrode material, lithium manganate material, to ensure the state in full power in terms of molecular structure, lithium ion batteries have been completely embedded into the carbon anode hole, fundamentally avoid dendrite. At the same time, solid structure LiMn2O4, the oxidation resistance is far lower than the decomposition temperature than the cobalt acid lithium cobalt acid lithium 100 degrees, even if the internal short circuit occurs due to the external force (acupuncture), external short circuit, overcharge, also can avoid the danger caused by precipitation of lithium metal combustion and explosion. In addition, the use of lithium manganate material can also greatly reduce costs.
2, to improve the performance of the existing safety control technology, first of all, to improve the safety performance of the lithium-ion battery core in the 12.8V lithium battery pack, which is particularly important for high-capacity batteries. Choose a diaphragm with good thermal shutdown. The diaphragm acts as a barrier to allow the passage of lithium ions while isolating the positive and negative cells of the battery. When the temperature increases, the diaphragm is closed before melting, so that the internal resistance rises to 2000 ohms, so that the internal reaction stops.
3. When the internal pressure or temperature reaches the preset standard, the explosion proof valve will be opened, and the pressure will be started to prevent excessive accumulation of internal gas, deformation, and eventually lead to shell burst.
4, improve the sensitivity of control, select more sensitive control parameters and adopt multiple parameters of joint control (which is particularly important for large capacity batteries). For large capacity lithium ion battery pack is composed of series / parallel multiple batteries, such as voltage of notebook computer is more than 10V and larger capacity, generally use 3 ~ 4 single cells in series can meet the voltage requirements, and then 2 to 3 series of batteries in parallel, to ensure greater capacity.
5, large capacity battery itself must set up more perfect protection function, also should consider two kinds of circuit board module: protection circuit board (Protection Board PCB) module and Smart Battery Gauge Board module. The whole battery protection design includes: first level protection IC (to prevent battery overcharge, over discharge, short circuit), second level protection IC (prevent second overvoltage), fuse, LED indicator, temperature adjustment and other components.
6, in the multilevel protection mechanism, even in the power supply charger, notebook computer abnormal circumstances, can only turn the laptop battery automatic protection, if the situation is serious, often in the plug after working, not explode.
7, laptop and mobile phone use of lithium-ion batteries based on the underlying technology is not safe, industrial lithium battery needs to consider more secure structure. In short, with the progress of materials technology and people's understanding of the design, manufacture, testing and use of lithium-ion batteries, the future lithium ion battery will become safer.
8, whether positive or negative active material will have the problem of expansion and contraction, the general negative carbon material 20% (theoretical value: 10.5%) expansion and contraction, and as the cathode material LFP 6% (theoretical value: 2%) expansion yield. When the times of charge and discharge, between the positive and negative active material particles contact less, increase the gap, and even some from the collector, resulting in electron and ion transmission path of intermittent non continuous phase, become the active material of death, is no longer involved in the electrode reaction. As a result, the cycle life decline. VGCF carbon tube has a large aspect ratio. Even if the positive and negative active materials expand and shrink, the gap between the active particles can be bridged by VGCF carbon tube, and the electron and ion transmission will not be interrupted.
Five, lithium battery design specifications notice:
1, lithium ion batteries can be seen everywhere in people's lives, a variety of portable electronic products, vehicle GPS, lithium-ion batteries become the important components to maintain the operation of these tools. Maintaining lithium-ion battery moderate charge and discharge can extend battery life. Lithium ion battery maintenance at 10%~90% is good for battery protection. That means it doesn't need to reach maximum when charging batteries for digital products such as mobile phones, laptops and so on.
2, equipped with a lithium ion battery digital products exposed to sunlight or store in a hot car, the best of these products will be closed, the reason is that if the operating temperature exceeds 60 degrees Celsius, will accelerate the aging of lithium ion battery. Lithium battery charging temperature range: 0~45 degrees Celsius, lithium battery discharge temperature range 0~60 degrees celsius.
3, if the cell phone battery needs to be recharged every day, the reason may be that the battery is defective or that it should be retired. For laptop owners, if you plug the plug for a long time, you'd better remove the battery (the high heat generated during the use of the computer is harmful to the laptop battery).
4, usually, the 50% power is most conducive to lithium ion battery storage; if the long-term use of external power supply for notebook computers, or battery power has exceeded 80%, immediately remove the battery. Usually the charge does not need to fill the battery, charge to about 80% can be. Adjust the operating system power options, the electricity alarm to more than 20%, usually the minimum battery power should not be less than 20%.
By PACK cell network finishing exchange write, we are professional PACK battery manufacturers, a lithium battery PACK rich design experience, there are a lot of code for design of lithium battery PACK case, view the site map, to learn more about PACK lithium battery safety design specification summary.