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Basic knowledge of battery maintenance

长兴新能源 2021-07-09 16:20 Industry
1. What is the difference between primary and charging batteries?
 
The electrochemical properties of the battery decide whether the type of battery can be charged. According to their electrochemical composition and the structure of the electric * it can be seen that the reaction between the internal structure of the real rechargeable battery is reversible.
 
Theoretically, this reversibility is not affected by the number of cycles. Since the charge and discharge will cause reversible changes in the volume and structure of the electric * battery, the internal design of rechargeable battery must support the change. Since, the battery only does one discharge at a time, its internal structure is much simpler and does not need to support the change. Therefore, it is not possible to charge the primary battery, This is dangerous and uneconomic. If it needs to be reused, there should be a choice of charging batteries with real cycles of about 1000 times. This battery can also be called primary battery or battery.
 
2. Is there any other difference between primary and secondary batteries?
 
Another obvious difference is their energy and load capacity, as well as self discharge rate. The secondary battery energy is much higher than that of primary battery, but their load capacity is relatively small.
 
3. What are the advantages and disadvantages of rechargeable portable batteries?
 
The battery has a long life and can be cycled for more than 1000 times. Although the price is higher than that of dry battery, it is more cost-effective if it is used frequently. Charging batteries have a lower capacity than alkaline manganese or zinc carbon batteries of the same specification, such as faster discharge.
 
Another disadvantage is that it is difficult to predict when the discharge will end because of their nearly constant discharge voltage. When the discharge is over, the battery voltage will suddenly decrease. If you use it on a camera, suddenly the battery is discharged, it will have to be terminated.
 
But on the other hand, rechargeable batteries can provide more capacity than too many primary batteries.
 
However, Li ion battery can be widely used in photographic equipment, because of its high capacity, high energy density and gradually decreasing discharge voltage with the increase of discharge depth.
 
4. How does the charging battery realize its energy conversion?
 
Each battery has the ability of electrochemical conversion, namely, the stored chemical energy is directly converted into electric energy. In the case of secondary electrons (also called battery), in the discharge process, chemical energy is converted into electric energy; In the process of charging, the electric energy is converted into chemical energy again. According to the different electrochemical system, this process can be charged and discharged more than 500 times, while Li ion can be recharged and discharged more than 1000 times. Li ion is a new type of rechargeable portable battery. Its rated voltage is 3.6V, and its discharge voltage will decline with the depth of discharge. Unlike other charging batteries, the voltage suddenly decreases when the discharge is not.
 
5. What is Li ion battery?
 
Li ion is the development of lithium battery. So before introducing Li ion, we introduce lithium battery. For example, the button batteries used in cameras used to be lithium batteries. The positive * material of lithium battery is lithium metal, and negative * is carbon. When charging the battery, lithium ion is generated on the positive * of the battery, and the lithium ion generated moves to negative * through the electrolyte. As a negative * carbon, it has many micropores. The lithium ions which reach negative * are embedded in the pores of carbon layer. The more lithium ions are embedded, the higher the charging capacity. Similarly, when the battery is discharged (that is, the process we use the battery), the lithium ions embedded in the negative carbon layer are removed and moved back to positive. The more lithium ions are positive, the higher the discharge capacity is. What we usually call battery capacity is discharge capacity. During the charging and discharging of Li ion, lithium ion is in the state of motion from positive to negative * → positive. Li ion is like a rocking chair, with two ends of the battery on both ends, while lithium ion runs back and forth like an athlete. So Li ion is also called rocking chair battery.
 
6. What are the components of Li ion battery?
 
(1) The upper and lower cover of the battery (2) positive * - the active material is cobalt oxide (3) diaphragm -- a special composite membrane
 
(4) Negative * - active substance is carbon (5) organic electrolyte (6) battery shell (divided into steel shell and aluminum shell)
 
7. What are the advantages of Li ion batteries? What are the disadvantages?
 
Li ion has the following advantages:
 
1) The operating voltage of the single cell can reach 3.6-3.8v:
 
2) The specific energy is large, and the actual specific energy can be reached at present is 100-115wh/kg and 240-253wh/l (twice as much as NL CD, 1.5 times as Ni MH). With the development of technology, the specific energy can reach 150wh/kg and 400wh/l in the future
 
3) The cycle life is long, can reach 500 times or more, even 1000 times. For the electric appliances with small current discharge, the battery life will multiply the competitiveness of the electrical appliances
 
4) As the predecessor of Li ion, lithium battery has the advantages of good safety, no pollution and no memory effect. Because lithium metal is easy to form dendrite and short circuit, it reduces its application field: the elements without cadmium, lead and mercury in Li ion have environmental pollution: the major disadvantage of Ni Cd batteries with some processes (such as burning type) is "memory effect", which seriously restricts the use of batteries, But Li ion has no problem in this area at all.
 
5) Small self discharge
 
The self discharge rate of Li ion filled with electricity at room temperature is about 10% after one month storage, which is much lower than 25-30% of Ni Cd and 30-35% of Ni MH. Li ion also has some disadvantages, such as:
 
1) The cost of the battery is high. The main reason is that the price of LiCoO2 is high (the co resource is small), and the purification of electrolyte system is difficult.
 
2) No high current discharge. Due to the organic electrolyte system, the internal resistance of the battery is larger than that of other batteries. Therefore, it is required to have a small discharge current density, and the discharge current is below 0.5c, which is only suitable for the use of small and medium current appliances.
 
3) Line control needs to be protected.
 
A. Overcharge protection: overcharge of battery will destroy positive * structure and affect performance and life; At the same time, overcharge causes electrolyte to decompose, and the internal pressure is too high, which leads to leakage of liquid and other problems; Therefore, it is necessary to charge at constant pressure of 4.1v-4.2v;
 
B. Over discharge protection: over discharge will cause the recovery of active substances difficult, so protection line control is also needed.
 
8. What is the lithium ion manufacturing process?
 
1) Ingredients
 
The slurry positive and negative * substances are made by mixing the special solution and adhesive with the powder positive and negative * active substances respectively, and then mixing them evenly at high speed.
 
2) Desert painting
 
The slurry is evenly coated on the surface of the metal foil, dried, and made into positive and negative * * pieces respectively.
 
3) Assembly
 
Put the positive diaphragm negative diaphragm in the order of top-down. The battery core is made by winding. The assembly process of the battery is completed through the process of injecting electrolyte and sealing. Make finished battery.
 
4) To become
 
The finished battery is tested by special battery charging and discharging equipment, and each battery is tested. Select qualified finished battery and leave factory.
 
9. How to realize the safety characteristics of lithium ion?
 
In order to ensure the safe and reliable use of Li ion, experts have carried out a very strict and thorough battery safety performance design to meet the battery safety assessment index.
 
1) Diaphragm 135 ℃ automatic shut-off protection
 
Celgars2300 PE PP PE three-layer composite membrane was used. When the temperature of the battery reaches 120 ℃, the membrane holes on both sides of PE composite film are closed, the internal resistance of the battery increases, the temperature rise inside the battery slows down. When the temperature rise of the battery reaches 135 ℃, the PP membrane hole is closed, the battery is open circuit, and the battery will no longer rise temperature, so as to ensure the safety and reliability of the battery.
 
2) Add additives to electrolyte
 
Under the condition of overcharge and battery voltage higher than 4.2V, electrolyte additives polymerize with other substances in the electrolyte, and the internal resistance of the battery increases greatly, and a large area of open circuit is formed inside the battery, and the battery will no longer rise temperature.
 
3) Composite structure of battery cover
 
The battery cover is made of a mark explosion-proof ball structure. When the battery is heated, some gas generated during the activation process of the battery expands, the pressure inside the battery increases, and the pressure reaches a certain degree of notch rupture and gas bleeding.
 
4) Various environmental abuse tests
 
The safety of the battery was investigated by various abuse experiments, such as external short circuit, overcharge, acupuncture, impact, incineration, etc. At the same time, the temperature shock test and vibration, drop, impact and other mechanical properties of the battery are carried out to investigate the performance of the battery in the actual environment.
 
10. What charge limiting voltage? Rated capacity? Rated voltage? Termination voltage?
 
A. Charging limiting voltage
 
According to the manufacturer's regulations, the voltage value of the battery when the battery is transferred from constant current charging to constant voltage charging.
 
B. Rated capacity
 
The battery capacity indicated by the manufacturer refers to the power supply when the battery is discharged to the termination voltage at an ambient temperature of 20 ℃ ± 5 ℃ at a rate of 5h, expressed in C5, in ah (ampere hour) or MAH (MAH hours).
 
C. Nominal voltage
 
Used to represent an approximate value of the battery voltage.
 
D. Termination voltage
 
The load voltage of the battery at the end of discharge is specified, and its value is n * 2.75V (the number of series of lithium-ion monomer cells is expressed as "n").
 
11. Why is the constant voltage charging current decreasing gradually?
 
Because when the constant current process ends, the electrochemical * inside the battery will remain at the same level, constant voltage process and constant electricity in the whole constant current
 
Under the field, the concentration difference of li+ in the internal is gradually eliminated, and the mobility and velocity of the ions are shown as the current gradually decreases.
 
12. What is the capacity of the battery?
 
The capacity of the battery is divided into rated capacity and actual capacity. The rated capacity of the battery refers to the battery should be discharged * low limit under certain discharge conditions when designing and manufacturing the battery. Li ion specifies that the battery is charged for 3 hours under the control of normal temperature and constant current (1c) constant voltage (4.2V). The actual capacity of the battery refers to the actual power discharged by the battery under certain discharge conditions, which is mainly affected by the discharge ratio and temperature (so strictly speaking, the battery capacity should indicate the charging and discharging conditions). The common units of capacity are: MAH, ah=1000mah).
 
13. What is the internal resistance of the battery?
 
Refers to the resistance of the current flowing through the inside of the battery when the battery is working. It has two parts: ohmic internal resistance and * internal resistance. The high internal resistance of the battery will lead to the decrease of the working voltage and the shorter discharge time. The internal resistance is mainly affected by the materials, manufacturing technology and battery structure. It is an important parameter to measure the performance of the battery. Note: the internal resistance in charging state is generally taken as the standard. The internal resistance of the battery shall be measured by a special internal resistance meter, but not by the multimeter ohm.
 
14. What is open circuit voltage?
 
It refers to the potential difference between positive and negative * of the battery when the battery is not in working state, i.e. when the circuit has no current flowing through. Generally, the open circuit voltage of Li ion is about 4.1-4.2v after full charge and about 3.0V after discharge. The battery charging state can be judged by the open circuit voltage of the battery.
 
15. What is the working voltage?
 
Also known as end voltage, refers to the battery in the working state, that is, the current in the circuit obsolete battery between positive and negative * potential difference. In the discharge state of the battery, when the current flows through the inside of the battery, it is not necessary to overcome the resistance caused by the internal resistance of the battery, so the working voltage is always lower than that of the open circuit battery, and the opposite is applied when charging. The discharge voltage of Li ion is about 3.6V.
 
16. What is a discharge platform?
 
The discharge platform is the discharge time when the constant voltage is charged to 4.2V and the electric current is less than 0.01c, and then it is left for 10 minutes to discharge to 3.6V under any discharge current of each rate. It is an important standard to measure the quality of batteries.
 
17. What is the ratio of charge discharge? Time rate?
 
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 data value, usually expressed in the letter C. If the nominal rated capacity of the battery is 600mah, 1c (1-fold), 300mAh is 0.5c, 6a (600mah) is 10C. and so on
 
The time rate is also called the hour rate, which refers to the hours required for the battery to complete its rated capacity with a certain current. For example, the rated capacity of the battery is 600mah, and the rated capacity is 1 hour when the current of 600mah is used, so the current of 600mah is 1 hour rate, and so on
 
18. What is the self discharge rate?
 
Also known as the charge retention capacity, refers to the battery in open circuit state, the battery stored in a certain condition of the capacity to maintain. It is mainly affected by the factors such as battery manufacturing technology, materials, storage conditions, etc. It is an important parameter to measure the performance of the battery.
 
Note: after 100% of the battery is open circuit is put on hold, the self discharge is normal to a certain extent. Open circuit is used for 28 days under open condition at 20 ± 2 ℃ after Li ion specified in GB standard. Battery capacity loss is allowed.
 
19. What is internal pressure?
 
It refers to the internal pressure of the battery, which is caused by the gas produced by the sealed battery during the charging and discharging process, which is mainly affected by the battery materials, manufacturing technology, battery structure and other factors. The main reason is that the gas from the decomposition of the water and organic solution in the battery accumulates in the battery.
 
The continuous overcharge with high ratio will lead to the increase of temperature and internal pressure of the battery, and will have destructive effects on the performance and appearance of the battery in serious cases, such as liquid leakage, drum bottom, increase of internal resistance of the battery, shorter discharge time and cycle life.
 
Any form of Li ion over operation will cause serious damage to battery performance, even explosion. In order to avoid overcharge, Li ion should adopt constant current and constant voltage charging method in the charging process.
 
20. Why does the battery have to be stored for a while before it can be packed and shipped?
 
The storage performance of the battery is an important parameter to measure the stability of the battery comprehensive performance. After a certain period of storage, the capacity and internal resistance of the battery can be changed to a certain extent. After a period of storage, the electrochemical performance of the internal components can be stabilized, and the self discharge performance of the battery can be understood so as to ensure the quality of the battery.
 
21. Why should it be transformed?
 
After the battery is manufactured, the process of activating the positive and negative * substances inside the battery through certain charging and discharging methods to improve the charge discharge performance, self discharge and storage performance of the battery
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