18650 battery 3.7v 1800mah

　　Problem analysis and research on substation 18650 battery 3.7v 1800mah

　　statement of problem:

　　At present, most of the 18650 battery 3.7v 1800mah in the DC system of the substations under our company's jurisdiction have been updated to valve-regulated sealed lead-acid 18650 battery 3.7v 1800mah. There are two important factors that affect the use of valve-controlled 18650 battery 3.7v 1800mah: temperature and float charge voltage. Changes in temperature and float charge voltage will bring serious harm to the valve-controlled sealed battery, seriously affecting the service life and real-time capacity. The current operating environment temperature of our 18650 battery 3.7v 1800mah Basically, it is less than an ideal constant value, which is very detrimental to the safe and stable operation of valve-regulated lead-acid 18650 battery 3.7v 1800mah.

　　Cause Analysis:

　　Features of valve-regulated sealed 18650 battery 3.7v 1800mah: Valve-regulated sealed lead-acid 18650 battery 3.7v 1800mah use cathode absorption electrochemical principles and unique structurally designed materials to ensure the establishment of oxygen cycle recombination in the battery. The oxygen cycle chemical reaction equation:

　　Compared with traditional acid-proof and explosion-proof lead-acid 18650 battery 3.7v 1800mah, it has the following characteristics: (1) Sealed design, working in lean liquid state, no need to add distilled water;

　　(2) No need to measure electrolyte density; (3) Can be placed in any direction; (4) Basically no harmful gases, little environmental pollution; (5) High environmental temperature requirements.

　　one. Effect of temperature:

　　The float charge current of the valve-regulated sealed battery is extremely sensitive to temperature. Every time the temperature changes by 10°C, the current changes exponentially. Under the same charge current, the temperature increases and the float charge voltage decreases. Therefore, if temperature compensation is not performed, the controller may shut down prematurely and the battery is not actually fully charged, causing the battery to form a memory effect in the long term and reducing capacity; overcharging causes the battery to act as a water electrolyzer, causing overheating and water loss, causing electrolysis fluid loss, causing battery failure.

　　The capacity of a valve-regulated battery is 100% when the ambient temperature is 25°C; when it exceeds 25°C, the battery water will be lost, increasing the electrolyte concentration; secondly, high battery temperature will accelerate the corrosion rate of the alloy. The battery grid in an environment may be perforated and damaged, which may easily cause the active material to weaken and fall off. It can be seen from this that although the increase in ambient temperature temporarily increases the capacity, the high temperature causes the battery grid corrosion to increase dramatically, seriously hindering the electrode reaction and reducing the overall battery capacity. The following is the relationship between temperature and capacity of Shenzhen Huada valve-regulated battery below 25℃, as shown in the table:

　　The design capacity of Enos-Huada 18650 battery 3.7v 1800mah changes with temperature, and a drop in temperature has a significant impact on the capacity.

　　The following is the relationship curve between temperature and capacity of Shandong Huari SNS valve-controlled sealed battery (the float charge voltage is constant at the standard value of 25°C):

　　Ce—25°C baseline capacity; t—battery temperature at the start of discharge;

　　Ct—actually measured capacity; K—temperature coefficient, the 10-hour rate is K=0.006/℃

　　The design life of the Enos-Huada GFM battery changes with the operating temperature. For every 10°C increase in temperature, the float charge life is halved. The following table shows the relationship between the battery float charge life and temperature:

　　From this table, it is easy to know that the service life of Shenzhen Huada valve-regulated sealed lead-acid 18650 battery 3.7v 1800mah is greatly affected by temperature and float voltage.

　　The following is the relationship curve between temperature and life of Shandong Huari SNS valve-regulated sealed battery (the float charge voltage is constant at the standard value of 25°C):

　　This table is a life and temperature relationship diagram made in the laboratory by a Japanese company, a joint venture of Shandong Huari Factory. It can be seen from it that the impact of temperature rise on the battery is that the float charge voltage value remains unchanged at the standard temperature of 25°C. : The service life at 25°C is the design life, the service life at 30°C is about 75% of the design life, and at 35°C it is only about 55% of the design life. It can be seen from the above graphs and tables that the operating temperature of valve-regulated sealed lead-acid 18650 battery 3.7v 1800mah has a great impact on the service life.

　　two. Effect of float voltage:

　　Float charge operation is the best operating condition for the battery. The battery is always fully charged during operation. In theory, the battery will achieve the longest service life if operated under this condition. The setting of the float voltage has a very important impact on the life of the battery. The amount of current generated by the float voltage should meet the needs of compensating self-discharge and battery cell discharge and maintaining oxygen circulation. Unreasonable float voltage mainly affects the battery in two aspects, namely the corrosion rate of the positive electrode grid and the emission of gas in the battery. Especially when the float voltage of the battery exceeds a certain value, the grid corrosion phenomenon will be further intensified. The oxygen and hydrogen in the battery will generate higher pressure and be discharged through the exhaust valve, causing the battery to lose water. Corrosion of the positive electrode means that the battery Loss of water further aggravates battery degradation and shortens its life. If the float charge voltage exceeds a certain range, the increased float charge current will produce more surplus gas, which will cause resistance to oxygen recombination at the negative electrode, thereby weakening the oxygen cycle function and seriously reducing the lifespan. The following are the float voltage and life test results of the American GNB valve-regulated sealed battery (the standard float voltage of this type of battery is 2.27V at 25°C):

　　It can be said that inappropriate float voltage value has a relatively large impact on the service life of valve-controlled sealed 18650 battery 3.7v 1800mah.

　　solution:

　　one. The battery room is equipped with heating facilities, and the temperature can be maintained between 20°C and 25°C. The temperature change range has little impact and can operate normally.

　　two. If there is no heating facility in the battery room, or the temperature does not meet the regulatory requirements (this is the case in most maintenance substations in our location), temperature compensation is used to change the floating charge voltage. The temperature compensation coefficient of a general valve-regulated sealed lead-acid battery is that for every 1 degree increase in temperature, the corresponding float voltage value should be reduced by 3mV. The following figure shows the requirements for Shenzhen Huada battery float voltage changes with temperature:

　　If the temperature in winter reaches 0°C, according to such a temperature compensation, the float charge voltage should be increased by about 8V. For example, Shenzhen Huada's valve-regulated battery requires compensation of 5mV per degree, so the float charge voltage that needs to be increased is as much as 13V. At present, many substations we maintain do not have temperature compensation. There are two main reasons: first, some substations do not have temperature compensation devices, and secondly, even the stations with temperature compensation devices are not running due to various reasons. From the previous analysis, we can see that the harm is considerable.

　　The first solution is to propose a more stable temperature sensor and corresponding voltage regulation control to the manufacturer; the second is that we can increase the maintenance work on valve-controlled sealed lead-acid 18650 battery 3.7v 1800mah and artificially change the float voltage value, which can be ranged according to seasons. Internal changes can make the float charge voltage deviate from the standard value smaller, and to a large extent, it can also effectively suppress the harm caused by the float charge voltage deviating from the real-time standard value.

　　three. The DC inspection system for substations is strictly implemented. The 220kV substation is inspected more than twice a year and the 110kV substation is inspected every year to ensure the accuracy of the battery float charging voltage.

　　The above is an analysis of the current problems in the float charging operation of valve-controlled sealed lead-acid 18650 battery 3.7v 1800mah in substations. We hope it can provide help for the safe and stable operation of the substation DC system. Inappropriateness is inevitable, please criticize and correct me, it will be greatly appreciated.

　　references:

　　1. Beijing Electric Power Company substation DC system management system

　　2. Technical regulations for DC system of Beijing Electric Power Company’s substations

　　3. Instructions for Shandong Huari, Qufu Shengyang, and Shenzhen Huada valve-regulated sealed lead-acid 18650 battery 3.7v 1800mah;

　　4. U.S. GNB valve-regulated sealed lead-acid battery operation and maintenance rules

　　5. Compilation of DC system documents from the Production Technology Department of North China Power Grid Co., Ltd.

　　6. Questions and Answers on Practical Technology of Valve Regulated Lead-Acid 18650 battery 3.7v 1800mah China Electric Power Press

　　7. Practical technology of valve-regulated lead-acid 18650 battery 3.7v 1800mah China Electric Power Press

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