Lithium-ion batteries can only be charged and discharged 500 times?
I believe most consumers have heard that the lifespan of a lithium battery is “500 times”, 500 times of charging and discharging. After this number of times, the battery will “end its life”. in order to extend battery life If the battery is completely drained every time, does it really extend battery life? the answer is negative. The lifespan of a lithium battery is "500 times", which does not refer to the number of charges, but to one cycle of charging and discharging.
A charge cycle means that all of the battery's energy is used from full to empty, then charged from empty to full. This is not the same as a single charge. For example, a lithium battery only uses half its power the first day, then it is fully charged. If it is always the same the lentomorrow, that is, if you charge it half and charge it twice in total, it can only be counted as one charging cycle and not two. Therefore, multiple charges may often be required to complete a cycle. Each time a charge cycle is completed, the battery capacity decreases a little. However, this power reduction is very small. High quality batteries retain 80% of their original capacity after multiple charge cycles. Many lithium-ion powered products are still used as usual after two or three years. Of course, lithium batteries still need to be replaced once their lifespan is reached.
The so-called 500 times means that the manufacturer has achieved approximately 625 times of charging at a constant discharge depth (e.g. 80%), reaching 500 charge cycles.
(80%*625=500) (ignoring factors such as capacity reductionlithium battery)
Due to various influences in real life, especially the depth of discharge during charging is not constant, so 500 charging cycles can only be used as a reference for battery life. Lithium batteries can generally be charged and discharged 300 to 500 times. It is better to partially discharge lithium batteries than to fully discharge them, and to avoid frequent full discharges. Once the battery leaves the production line, the clock starts ticking. Whether you use it or not, the lifespan of lithium batteries only lasts the first few years. The decrease in battery capacity is due to an increase in internal resistance caused by oxidation (which is the main cause of the decrease in battery capacity). Eventually, the cell resistance reaches a point where, even though the battery is cfully charged, it is unable to release stored energy.
The aging rate of lithium batteries is determined by temperature and state of charge. The table below illustrates the reduction in battery capacity for both settings.
Charging temperature 40% charging 100%
Capacity 0°C after one year Capacity 98% after one year Capacity 94%
Capacity 25°C after one year 96% Capacity 80% after one year
40°C Capacity 85% after one year Capacity 65% after one year
60°C Capacity 75% after one year Three months later Capacity 60%
As shown in the figure, a high state of charge and increased temperature accelerate the decline in battery capacity.
If possible, try to recharge the battery to 40% and place it in a cool place. This allows the battery's own protection circuits to operate for a long life. If the battery is exposed to high temperatures after beingIf fully charged, this will cause serious damage to the battery. (So when we use fixed power supply, the battery is fully charged and the temperature is usually between 25-30°C, which will damage the battery and cause its capacity to decrease).
Influence factor 1: Depth of discharge and recharge time
From the data on the left image obtained from the experiment, we can know that the recharge times are related to the depth of discharge. The greater the depth of discharge of the battery, the more rechargeable it can be, the less you need to recharge it.
The number of times recharged * depth of discharge = the total number of charging cycles completed, the higher the number of charging cycles completed, the longer the battery life, that is- i.e. the number of times rechargeable. * depth of discharge = actual battery life (ignoringt other factors)
Influence factor 2: overcharge, overdischarge and large charge and discharge current
Avoid overcharging the battery in any form. If the lithium-ion battery is overcharged, the battery will be seriously damaged and even explode.
Avoid deep discharge below 2V or 2.5V, as this may quickly and permanently damage the lithium-ion battery. Internal metal plating may occur, which may cause a short circuit and render the battery unusable or dangerous.
Most lithium-ion batteries have electronic circuits inside the battery that turn off if the battery voltage drops below 2.5 V, exceeds 4.3 V when charging or discharging, or if the battery current exceeds a predetermined threshold. the battery will be disconnected.
Avoid large charge and discharge currents, which exert pressureexcessive on the battery.
Influence factor 3: Overheating or excessive cooling environment
Temperature also has a significant impact on the lifespan of lithium batteries. Below freezing environments can cause lithium batteries to deplete as soon as electronic products are turned on, while overheating environments will reduce battery capacity. Therefore, if the laptop uses an external power source for a long time without removing the battery, the battery will be exposed to the high heat emitted by the laptop for a long time and will soon be discarded.
Influence factor 4: Fully charged or discharged state for a long time
Excessively high and low power states have a negative impact on the life of lithium batteries . The number of repeated charges indicated on the plupart of electrical appliances or batteries sold is based on 80% discharge as a benchmark test. Experiments show that for some notebook lithium batteries, if the battery voltage often exceeds the standard voltage of 0.1 volt, that is, from 4.1 volts to 4.2 volts, the Battery life will be cut in half. If it increases by 0.1 volt, the battery life will be cut in half. lifespan will be reduced to 1/3; The more fully you charge the battery, the greater the battery loss will be. A long-term low or no power condition will increase the resistance to the movement of electrons inside the battery, resulting in a smaller battery capacity. It is best for lithium batteries to be in an intermediate state of charge, where they have the longest life.
From the above, we can summarize the following points thatcan extend the capacity and life of lithium batteries. If you use external power for your laptop for a long time If the computer is turned on or the battery charge has exceeded 80%, remove the battery immediately. There is no need to fully charge the battery during normal charging, just charge it to around 80%. Adjust the operating system power options and set the power alarm above 20%. The minimum battery power should not be less than 20%. For mobile phones and other small electronic devices, you should unplug the power cord (including the USB interface for charging function) immediately after charging. Keeping it connected will damage the battery. Charge frequently, but it is not necessary to fully charge the battery. Whether it's a laptop or a teemobile phone, be careful not to let the battery run out (automatic shutdown). If you're traveling, keep the battery fully charged, but continue to charge your devices whenever conditions permit. Use a smarter, more energy-efficient operating system. First, keeping lithium-ion batteries properly charged and discharged can extend battery life. Keeping the lithium-ion battery power between 10% and 90% is beneficial to protect the battery. This means that when charging batteries of digital products such as mobile phones and laptops, it is not necessary to reach the maximum value.
If digital products equipped with lithium-ion batteries are exposed to sunlight or stored in hot cars, it is best to keep these products turned off because if the operating temperature exceeds 60 degrees Celsius, the battery will become lithium-ion will accelerate aging.
Lithium battery charging temperature range: 0-45 degrees Celsius, lithium battery discharge temperature range 0-60 degrees Celsius.
Second, if the cell phone battery needs to be charged every day, the reason may be that the battery is defective or it is time to "retire".
For laptop owners, it is best to remove the battery if it is plugged in for a long time (the high heat generated by the computer while in use is not good for the battery of the laptop).
Third, under normal circumstances, 50% power is most conducive to the preservation of lithium-ion batteries. 1. Primary lithium battery
Also called primary lithium battery. It can be discharged continuously or intermittently. Once the energy is exhausted, it can no longerbe used and it is widely used in low-power electronic products, such as cameras. Primary lithium batteries have a very low self-discharge and can be stored for 3 years. The effect will be better if stored in refrigerated conditions. It is a good idea to store primary lithium batteries in a low temperature location. Note: Primary lithium batteries are different from lithium-ion batteries, cannot be charged, and charging is very dangerous!
2. Lithium-ion battery
Also called secondary lithium battery. It can be stored for more than six months at 20°C because its self-discharge rate is very low and most of its capacity can be restored.
Lithium batteries have a self-discharge phenomenon. If the battery voltage is stored below 3.6V for a long time, the battery will overdischargevely and will damage the internal structure of the battery, thereby reducing the battery capacity. life. Therefore, lithium batteries stored for a long time should be recharged every 3 to 6 months, that is, charged to a voltage of 3.8 to 3.9 V (the optimal storage voltage of batteries lithium is approximately 3.85 V) and maintained at a depth of discharge of 40% to 60%, should not be full. Batteries should be stored in a dry environment between 4°C and 35°C or in moisture-proof packaging. Keep away from heat sources and do not expose to direct sunlight. The place for shooting.
Lithium batteries have a wide application temperature range. They can still be used outdoors during the northern winter, but their capacity will be significantly reduced if returned to room temperature, the capacity can be restored. For cylindrical lithium-ion batteries,The model number is usually 5 digits long. As shown in the table below. The first two numbers are the diameter of the battery and the middle two numbers are the height of the battery. The unit is millimeter. For example, the 18650 lithium battery has a diameter of 18 mm and a height of 65 mm. Model diameter (mm) Height (mm) abcde ab cd Conventional cylindrical lithium ion battery model table model rated capacity (mAh) rated voltage (V) end of discharge voltage (V) rated charging voltage (V) internal resistance (mΩ) diameter (mm) Height (mm) Reference mass (g) ICR18650 1800~2600 3.6-3.7 3.0 4.2 ≤70 18 65 45 ICR18490 1400 3.6-3.7 3.0 4.2 ≤70 18 49 34 ICR14650 1100 3.6-3.7 3.0 4.2 ≤80 14 65 27 ICR14500 800 3.6-3.7 3.0 4.2 ≤80 14 50 21 ICR14430 700 3.6-3.7 3.0 4.2 ≤80 14 43 18 js145007003.0V (used with lithium battery voltage regulator) 3.04.2≤8014 Battery model table modelcylindrical lithium-ion battery power 5021 rated capacity (mAh) Nominal voltage (V) End of discharge voltage (V) Nominal charge voltage (V) Internal resistance (mΩ) Diameter (mm) Height (mm) Reference mass ( g) INR18650 1200~1500 3.6 3.0 4.2 ≤60 18 65 45 INR18490 1100 3.6 3.0 4.2 ≤60 18 49 34 Cylindrical lithium ion lithium iron phosphate battery model table capacity nominal (mAh) nominal voltage (V) end of discharge voltage (V) nominal charge voltage (V) internal resistance ( mΩ) Diameter (mm) Height (mm) Reference mass (g) IFR26650 3000 3.2 2, 0 3.6 ≤80 26 65 94 IFR22650 1800 3.2 2.0 3.6 ≤80 22 65 67 IFR18650 1100 ~ 14003.2 2.0 3.6 ≤80 18 65 45 IFR18490 1000 3.2 2.0 3.6 ≤80 18 49 34 Note: Internal resistance ≤ mΩ means that when fully charged, the maximum discharge current is used for constant current discharge, when the internal resistance reaches how many mΩ, the battery is close to scrap metal
The bLithium-ion batteries have different operating voltages, such as 3.6 V or 3.7 V, due to the large number of positive electrode materials and different negative electrodes.
Rectangular lithium-ion battery
Rectangular lithium-ion battery is the most common lithium battery in life. It has many models and is widely used in MP3, MP4, mobile phones, models. aircraft and other products.
Prismatic lithium-ion batteries are divided into two types: metal shell packaging (silver-white hard shell) and aluminum plastic shell packaging (white-gray soft shell, which can be scratched with nails). Lithium-ion batteries or liquid lithium batteries are encapsulated in aluminum plastic shells and are polymer (polymer) lithium-ion batteries. It can be said that the chemical materials and electrochemical properties used in these twobatteries are similar. Physical batteries use certain colloidal substances to help the battery plates accommodate or absorb the electrolyte, thereby reducing the use of liquid electrolyte. Therefore, the battery packaging can be changed from a metal shell to an aluminum plastic shell.
The metal cased lithium battery case is the negative electrode, and the positive electrode is on the protrusion on one side of the battery; the positive and negative electrodes of the aluminum cast lithium battery are the negative electrode. two plates on one side of the battery, and the case is an insulator
For square lithium-ion batteries, the model number is usually 6 digits. As shown in the table below. The first two numbers correspond to the thickness of the battery to 1 decimal place; the two middle numbers correspond to the width of the battery; THElast two digits correspond to the length of the battery. The unit is millimeter. For example, lithium battery 606168 has a thickness of 6.0 mm, a width of 61 mm and a length of 68 mm. (Note: Due to the different packaging methods used by different battery manufacturers, the capacity of prismatic lithium-ion batteries of the same model varies within 300mAh)
The rated voltage of lithium-ion batteries prismatic ion is generally 3.6. ~3.7 V. The end of charge voltage is generally 4.2 V. Square lithium-ion battery model length (mm) width (mm) thickness (mm) rated voltage (V) rated charging voltage (V ) abcdef ef cd a.b 3.6～3.7 4.2
Lithium battery Why not use 22650
The overall size is not the main feature As long as the lithium batteries are the same type, the rated voltage is the same. Common voltages of monoce lithium batteriesThe voltages are 3.7 V (fully charged 4.2 V) and 3.2 V (fully charged lithium iron phosphate 3.6 V, commonly used in electric vehicles).
Are there any round lithium iron phosphate batteries?
The lithium battery is too heavy.
The effects of overweight lithium batteries include excessive positive electrode surface density, excessive positive electrode active materials, insufficient negative electrode supports, lithium ions precipitating on the surface of the negative electrode after deintercalation and lithium. precipitation, which causes battery capacity. If it is low, the cyclability of the battery becomes poor. If the surface density of the negative electrode is too high, the piece of electrode may be crushed to death when rolled, which will harm the penetration of lithium ions and affect the development of capacity. There is no prmajor security issues.
Lithium iron phosphate batteries from Pacific Automotive Network are round. If the cross section of the battery changes from round to rectangular, it is called blade battery, CTP battery or laminated battery. the volumetric energy density, but the quality The energy density remains unchanged. This is how the high-tech “cobalt-free laminated battery” appeared.
Cylindrical and square lithium iron phosphate batteries. For small energy storage products, lithium batteries less than 2 kWh will mainly choose cylindrical batteries. If it is a medium to large energy storage product, above 2 kWh, square batteries will be chosen.
1. The advantages of choosing cylindrical lithium iron phosphate batteries for small energy storage products include cylindrical lithium iron phosphate batteries 18650, 26650 and32650. These three models have the largest batch sizes on the market and are. The most common, there are also less commonly used cylindrical batteries, such as 18500 and 22650.
Advantage 1: The advantage of using cylindrical batteries is that they are easy to assemble and the structure can be modified. Like the 18650 battery, which has the largest batch size and is also the most common in the market, its size is very flexible and can be based on structural design requirements. For example, a battery of 4 series and 8 parallels can be organized. in 4*8 or 16*2 arrangement, the size is very flexible.
Advantage 2: It can meet the needs of small capacity batteries. For example, lithium iron phosphate battery products require a 12.8V 1500mAh battery. Square batteries are generally large capacity and cannot meet the requirements. At present,the only choice is 18650-3.2V-1500mAh lithium iron phosphate battery cell. 4 strings and 1 parallel can meet the needs.
Advantage 3: When the cylindrical battery is assembled, the space between cells is large and the heat dissipation is good. The cylindrical battery, coupled with the battery cell holder, has a stable structure, large battery cell gaps and better heat dissipation.
2. Advantages of choosing square lithium iron phosphate for medium and large energy storage products
1: Square batteries have large capacity, and large lithium batteries can be combined and used. the battery count is smaller and consistency has improved as a result. For example, if a 72V 100Ah lithium iron phosphate battery is made from a 3.2V 100Ah square lithium iron phosphate battery, it only requires 20series, 1 parallel and 20 cells. If you use a 32650 6Ah cylindrical lithium iron phosphate battery, you need 20 cells in series and 17 cells in parallel, using 340 cells. The consistency of the battery is also related to the number of cells. The more cells, the worse the coherence will be and the battery performance will also be affected. The worse it is.
Advantage 2: The battery has a simple process and is easy to process. For large lithium batteries, using square batteries, you can use the positive and negative electrode lock nut method, or the laser welding process, which is simple and convenient. If you use a cylindrical battery, you still need to spot weld nickel strips, which is a complicated process and inconvenient to deal with. There are currently also cylindrical batteries that use welding technologye with aluminum wire, which is expensive and gives unsatisfactory results. Large square aluminum batteries are very convenient to process.
(Images/Text/Photos: Pacific Automotive Network Calling the Beast Q&A)