NiMH No.7 batteries

What is a high-rate NiMH No.7 batteries? High-rate lithium iron phosphate battery cycle life

What is a high-rate NiMH No.7 batteries? High-rate lithium iron phosphate battery cycle life. A high-rate NiMH No.7 batteries means that the battery can discharge at a large current. The rate of a NiMH No.7 batteries is related to the raw materials and process of the battery. Lithium-ion batteries are divided into high-rate batteries and lithium-ion batteries. Currently, mobile phones and laptops use lithium-ion batteries, which are usually commonly referred to as high-rate batteries. However, real high-rate batteries are rarely used in daily electronic products because of their high risk.

What is a high-rate NiMH No.7 batteries?

The discharge rate of a NiMH No.7 batteries refers to the current value required for the battery to discharge its rated capacity within a specified time. It is equal to the multiple of the rated capacity of the battery in terms of data value, usually represented by the letter C. For example, if the nominal rated capacity of the battery is 600mAh, it is 1C (1 rate), 300mAh is 0.5C, 6A (600mAh) is 10C, and so on.

High-rate batteries generally refer to lithium iron phosphate batteries. Lithium-ion batteries are a type of high-rate charging battery that relies mainly on the movement of lithium ions between the positive and negative electrodes to work. During the charging and discharging process, Li+ is embedded and de-embedded between the two electrodes: when charging the battery, Li+ is de-embedded from the positive electrode and embedded into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; when discharging, the opposite is true. Batteries that generally use materials containing lithium elements as electrodes. They are the representative of modern high-performance batteries.

Lithium-ion batteries have high energy density and high average output voltage. Low self-discharge, good batteries, less than 2% per month (recoverable). No memory effect. The operating temperature range is wide from -20℃ to 60℃. Excellent cycle performance, fast charging and discharging, charging efficiency up to 100%, and high output power. Long service life. It does not contain toxic and harmful substances and is called a green battery.

The charging process of high-rate lithium iron phosphate batteries is divided into two stages: constant current fast charging stage and constant voltage current decreasing stage. In the constant current fast charging stage, the voltage of the NiMH No.7 batteries gradually increases to the standard voltage of the battery, and then enters the constant voltage stage under the control chip. The voltage no longer increases to ensure that it will not be overcharged, and the current gradually decreases to the set value as the battery power increases, and finally completes the charging. The power statistics chip can sample and calculate the battery power by recording the discharge curve. After repeated use, the discharge curve of lithium-ion batteries will change. Although lithium-ion batteries do not have memory effects, improper charging and discharging will seriously affect the battery performance.

How long is the cycle life of high-rate lithium iron phosphate batteries?

The so-called life of lithium iron phosphate batteries refers to the end of life when the capacity decays to 70% of the nominal capacity after the battery has been used for a period of time. The industry generally calculates the cycle life by the number of cycles of lithium-ion batteries fully discharged.

During use, irreversible electrochemical reactions will occur inside lithium-ion batteries, resulting in a decrease in capacity, such as the analysis of electrolytes, the deactivation of active materials, and the collapse of the positive and negative electrode structures, resulting in a decrease in the number of lithium ion insertions and deinsertions, etc. The test shows that higher discharge rates will lead to faster capacity decay. If the discharge current is low, the battery voltage will be close to the equilibrium voltage, and more energy can be released.

The high-rate lithium iron phosphate battery has a cycle number of about 2,500 times. The lithium-ion batteries processed by regular manufacturers generally have a cycle number of 2,000-3,000 times. Lithium iron phosphate batteries can generally be used for about 8 years; but if used in the south. The life of lithium iron phosphate batteries is even longer than 8 years. The theoretical life of lithium iron phosphate battery packs also exceeds 2,000 charge and discharge cycles. Even if it is charged once a day, it can last for more than five years. Generally speaking, daily household use is charged once every three days, and it can also be used for about eight years. However, due to the poor low-temperature performance of lithium iron phosphate batteries, the life of lithium iron phosphate batteries will be relatively longer in the southern region.

High-rate lithium iron phosphate batteries have stable output voltage, high output voltage, stable performance, large capacity, long service life, wide operating temperature range, good safety, and environmental protection and pollution-free. Therefore, there is a lot of room for improvement in the future development of lithium-ion batteries.

How to choose the discharge rate of lithium-ion batteries?

The discharge rate of lithium-ion batteries is generally represented by the letter ‘C’. 1C means that the maximum discharge current of the battery is 1 times discharge. For example, a 1000mAh 10C NiMH No.7 batteries means that the maximum discharge current of the battery is 10 times, and its maximum discharge current is: 10×1000mA=10A. Generally, we call lithium-ion batteries with 1C discharge standard batteries, 2C-10C discharge low-rate batteries, and those exceeding 10C high-rate batteries.

The important difference between rate batteries and traditional standard batteries lies in the difference in manufacturing process. Standard batteries and low-rate batteries are mostly made by pole piece winding process, while the internal pole pieces of high-rate batteries used for emergency start power supply are made by lamination process. This also indirectly provides a simple identification method. The winding process battery will be slightly thicker on both sides and the flatness is slightly worse, while the lamination process rate battery is quite flat and square.

Since high-rate lithium-ion batteries are designed to meet stringent high-current discharge requirements, they use thicker pole pieces and thicker lithium-ion isolation membranes. For the same volume, the capacity will be slightly reduced, but in terms of safety, the small amount of capacity sacrificed is not worth mentioning.

The above is an analysis of the cycle life of high-rate lithium-ion batteries and lithium iron phosphate batteries. High rate is a relative concept. The larger the C number of a NiMH No.7 batteries, the higher the rate of the battery.

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