32.What is the IEC standard cycle life test?
IEC stipulates that the standard cycle life test for NiMH batteries is:
After the battery is discharged at 0.2C to 1.0V/piece
01) Charge at 0.1C for 16 hours, then discharge at 0.2C for 2 hours and 30 minutes (one cycle)
02) Charge at 0.25C for 3 hours and 10 minutes, discharge at 0.25C for 2 hours and 20 minutes (2-48 cycles)
03) Charge at 0.25C for 3 hours and 10 minutes, discharge at 0.25C to 1.0V (49th cycle)
04) Charge at 0.1C for 16 hours, leave for 1 hour, and discharge at 0.2C to 1.0V (50th cycle). For NiMH batteries, repeat 1-4 for a total of 400 cycles, and the 0.2C discharge time should be greater than 3 hours; for NiCd batteries, repeat 1-4 for a total of 500 cycles, and the 0.2C discharge time should be greater than 3 hours.
33.What is the internal pressure of a battery?
Refers to the internal gas pressure of the battery, which is caused by the gas generated by the sealed battery during the charge and discharge process, and is mainly affected by factors such as battery materials, manufacturing processes, and battery structure. The main reason for its generation is that the gas generated by the decomposition of water and organic solutions inside the battery accumulates inside the battery. Generally, the internal pressure of the battery is maintained at a normal level. In the case of overcharge or over-discharge, the internal pressure of the battery may increase:
For example, overcharge, positive electrode: 4OH- - 4e → 2H2O + O2↑; ①
The generated oxygen reacts with the hydrogen released on the negative electrode to generate water 2H2 + O2 → 2H2O ②
If the speed of reaction ② is lower than that of reaction ①, the generated oxygen will not be consumed in time, which will cause the internal pressure of the battery to increase.
34.What is the standard charge retention test?
The IEC standard charge retention test for NiMH batteries is:
After the battery is discharged to 1.0V at 0.2C, it is charged at 0.1C for 16 hours. After storage for 28 days at a temperature of 20℃±5℃ and a humidity of 65%±20%, it is discharged to 1.0V at 0.2C. For NiMH batteries, the charge time should be greater than 3 hours.
The national standard stipulates that the standard charge retention test for lithium batteries is: (IEC has no relevant standards) the battery is discharged at 0.2C to 3.0/piece, then charged to 4.2V at 1C constant current and constant voltage, with a cut-off current of 10mA, stored at a temperature of 20℃±5℃ for 28 days, and then discharged to 2.75V at 0.2C. The discharge capacity is calculated and compared with the nominal capacity of the battery, which should be no less than 85% of the initial capacity.
35.What is a short circuit test?
Place a fully charged battery in an explosion-proof box with a wire with an internal resistance of ≤100mΩ to short-circuit the positive and negative poles. The battery should not explode or catch fire.
36.What is high temperature and high humidity testing?
High temperature and high humidity test for NiMH batteries:
After the battery is fully charged, store it under constant temperature and humidity conditions for several days and observe whether there is any leakage during the storage process.
The high temperature and high humidity test for lithium batteries is: (national standard)
Charge the battery to 4.2V at 1C constant current and constant voltage with a cut-off current of 10mA, then place it in a constant temperature and humidity chamber at (40±2)℃ and a relative humidity of 90%-95% for 48h, then take out the battery and place it at (20±5)℃ for 2h. Observe the appearance of the battery and it should be normal. Discharge it to 2.75V at 1C constant current, then perform 1C charge and 1C discharge cycles at (20±5)℃ until the discharge capacity is not less than 85% of the initial capacity, but the number of cycles shall not exceed 3 times.
37.What is the temperature rise experiment?
After the battery is fully charged, put it into an oven and heat it up from room temperature at a rate of 5℃/min. Keep the oven temperature at 130℃ for 30 minutes. The battery should not explode or catch fire.
38.What is a temperature cycling experiment?
The temperature cycling experiment consists of 27 cycles, each of which consists of the following steps:
01) The battery is placed from room temperature to 66±3℃, 15±5% for 1 hour.
02) Place the mixture at a temperature of 33±3℃ and a humidity of 90±5℃ for 1 hour.
03) Change the condition to -40±3℃ and leave for 1 hour
04) The battery is placed at 25°C for 0.5 hours
These four steps complete one cycle. After 27 cycles of testing, the battery should not leak, accumulate alkali, rust or have other abnormal conditions.
39.What is a drop test?
After fully charged, drop the battery or battery pack from a height of 1m onto a concrete (or cement) floor three times to obtain impacts in random directions.
4 0.What is the vibration experiment?
The vibration test method of NiMH battery is:
The battery was discharged to 1.0V at 0.2C, then charged at 0.1C for 16 hours, and left for 24 hours before being vibrated under the following conditions:
Amplitude: 0.8mm
Make the battery vibrate between 10 Hz and 55 Hz, increasing or decreasing the vibration rate by 1 Hz per minute.
The battery voltage change should be within ±0.02V, and the internal resistance change should be within ±5mΩ. (The vibration time is 90min)
The lithium battery vibration test method is:
The battery was discharged to 3.0V at 0.2C, then charged to 4.2V at 1C constant current and constant voltage, with a cut-off current of 10mA. After being left for 24 hours, it was vibrated under the following conditions:
The vibration test was conducted with a vibration frequency of 10 Hz to 60 Hz and then to 10 Hz in a cycle of 5 minutes and an amplitude of 0.06 inches. The battery was vibrated in three axes, with each axis vibrating for half an hour.
The battery voltage change should be within ±0.02V and the internal resistance change should be within ±5mΩ.
41.What is an impact test?
After the battery is fully charged, place a hard bar horizontally on the battery and drop a 20-pound weight from a certain height onto the hard bar. The battery should not explode or catch fire.
42.What is a penetration test?
After the battery is fully charged, use a nail of a certain diameter to pierce the center of the battery and leave the nail inside the battery. The battery should not explode or catch fire.
43.What is a fire experiment?
The fully charged battery is placed on a heating device with a special protective cover and burned without any fragments penetrating the protective cover.
Common battery problems and analysis
44.What certifications have the company’s products passed?
The company has passed ISO9001:2000 quality system certification and ISO14001:2004 environmental system certification; its products have obtained EU CE certification and North American UL certification, passed SGS environmental testing, and obtained Ovonic's patent license; at the same time, the company's products have been insured by PICC worldwide.
45.What precautions should be taken when using batteries?
01) Please read the battery manual carefully before use;
02) The electrical and battery contacts should be cleaned and wiped with a damp cloth if necessary. After drying, install them according to the polarity markings;
03) Do not mix old and new batteries, and do not mix batteries of the same model but different types, so as not to reduce the efficiency;
04) Disposable batteries cannot be regenerated by heating or charging;
05) Do not short-circuit the battery;
06) Do not disassemble or heat the battery, or throw it into water;
07) When electrical appliances are not used for a long time, the batteries should be removed and the switches should be turned off after use;
08) Do not discard used batteries at will. Try to separate them from other garbage to avoid polluting the environment.
09) Do not allow children to replace batteries without adult supervision, and small batteries should be placed out of reach of children;
10) The battery should be stored in a cool, dry place away from direct sunlight.
46.What are the differences between the various common rechargeable batteries currently available?
Currently, nickel-cadmium, nickel-metal hydride, and lithium-ion rechargeable batteries are widely used in various portable power devices (such as laptops, camcorders, and mobile phones). Each rechargeable battery has its own unique chemical properties. The main difference between nickel-cadmium and nickel-metal hydride batteries is that nickel-metal hydride batteries have a higher energy density. Compared with the same type of battery, the capacity of nickel-metal hydride batteries is twice that of nickel-cadmium batteries. This means that the use of nickel-metal hydride batteries can greatly extend the working time of the equipment without adding extra weight to the power device. Another advantage of nickel-metal hydride batteries is that they greatly reduce the "memory effect" problem that exists in nickel-cadmium batteries, making nickel-metal hydride batteries more convenient to use. Nickel-metal hydride batteries are more environmentally friendly than nickel-cadmium batteries because they do not contain toxic heavy metal elements. Li-ion has also quickly become the standard power source for portable devices. Li-ion can provide the same energy as nickel-metal hydride batteries, but it can reduce the weight by about 35%, which is crucial for power devices such as camcorders and laptops. The advantages of Li-ion having no "memory effect" and no toxic substances are also important factors that make it a standard power source.
The discharge efficiency of nickel-metal hydride (NiMH) batteries significantly decreases at low temperatures. Generally, the charging efficiency increases with temperature, but when the temperature rises above 45°C, the performance of the battery materials deteriorates at high temperatures, and the cycle life of the battery will be greatly shortened.
47.What is the rate discharge of a battery? What is the hourly rate discharge of a battery?
Rate discharge refers to the relationship between the discharge current (A) and the rated capacity (A•h) during discharge. Hour rate discharge refers to the number of hours required to discharge the rated capacity at a certain output current.
48.Why is it necessary to keep the batteries warm when shooting in winter?
Because the activity of active substances in digital cameras is greatly reduced when the temperature is too low, and they may not be able to provide the normal operating current of the camera. Therefore, when shooting outdoors in areas with low temperatures, special attention should be paid to keeping the camera or batteries warm.
49.What is the operating temperature range of lithium-ion batteries?
Charging -10—45℃ Discharging -30—55℃
50.Can batteries of different capacities be combined together?
If batteries of different capacities or new and old batteries are mixed together, leakage, zero voltage and other phenomena may occur. This is because during the charging process, the capacity difference causes some batteries to be overcharged and some batteries to be undercharged. During discharge, some batteries with high capacity are not fully discharged, while those with low capacity are over-discharged. This vicious cycle causes the batteries to be damaged and leak or have low (zero) voltage.
51.What is an external short circuit and what impact does it have on battery performance?
Connecting the two ends of the battery to any conductor will cause an external short circuit. Different battery types may have different serious consequences. For example, the electrolyte temperature rises, the internal air pressure rises, etc. If the air pressure value exceeds the battery cap pressure value, the battery will leak. This situation seriously damages the battery. If the safety valve fails, it may even cause an explosion. Therefore, do not short-circuit the battery externally.
52.What are the main factors that affect battery life?
01) Charging:
When choosing a charger, it is best to use a charger with a correct charging termination device (such as an overcharge prevention time device, a negative voltage difference (-dV) charging cut-off device, and an overheating prevention sensing device) to prevent the battery from shortening its service life due to overcharging. Generally speaking, slow charging can extend the battery life more than fast charging.
02) Discharge:
a.The depth of discharge is the main factor affecting the battery life. The higher the depth of discharge, the shorter the battery life. In other words, as long as the depth of discharge is reduced, the battery life can be greatly extended. Therefore, we should avoid over-discharging the battery to an extremely low voltage.
b. When the battery is discharged at high temperature, the battery life will be shortened.
c. If the electronic equipment is not designed to completely stop all current, if the equipment is left unused for a long time without removing the battery, the residual current may sometimes cause excessive consumption of the battery, resulting in over-discharge of the battery.
d. Mixing batteries of different capacities, chemical structures or charge levels, as well as old and new batteries, can cause excessive battery discharge and even reverse charging.
03) Storage:
If the battery is stored at high temperature for a long time, its electrode activity will decay and its service life will be shortened.
53.Can batteries be stored inside electrical appliances after use or when not in use for a long time?
If the appliance is not used for a long period of time, it is best to remove the battery and place it in a low temperature and dry place. Otherwise, even if the appliance is turned off, the system will still cause the battery to have a low current output, which will shorten the battery life.
54. What are the best storage conditions for batteries? Do batteries need to be fully charged for long-term storage?
According to IEC standards, batteries should be stored at a temperature of 20℃±5℃ and a humidity of (65±20)%. Generally speaking, the higher the battery storage temperature, the lower the remaining capacity, and vice versa. A refrigerator at 0℃-10℃ is the best place to store batteries, especially for primary batteries. Even if secondary batteries lose capacity after storage, they can be restored by recharging and discharging them several times.
Theoretically, there is always energy loss when batteries are stored. The inherent electrochemical structure of the battery itself determines that the battery capacity will inevitably be lost, mainly due to self-discharge. Usually the size of the self-discharge is related to the solubility of the positive electrode material in the electrolyte and its instability after heating (easy self-decomposition). The self-discharge of rechargeable batteries is much higher than that of primary batteries.
If you want to store the battery for a long time, it is best to store it in a dry and low-temperature environment and keep the remaining power of the battery at about 40%. Of course, it is best to use the battery once a month to ensure that the battery is in good condition and not to cause the power to completely drain and damage the battery.
55.What is a standard battery?
The battery that is internationally defined as the standard for measuring electric potential (potential). It was invented by American electrical engineer E. Weston in 1892, so it is also called the Weston battery.
The positive electrode of the standard battery is a mercurous sulfate electrode, the negative electrode is a cadmium amalgam metal (containing 10% or 12.5% cadmium), and the electrolyte is an acidic saturated cadmium sulfate aqueous solution, which is actually a saturated cadmium sulfate and mercurous sulfate aqueous solution.
56.What are the possible reasons for zero voltage or low voltage in a single cell?
01) The battery is short-circuited or overcharged or reverse-charged (forced over-discharge);
02) The battery is continuously overcharged with high rate and large current, causing the battery core to expand, the positive and negative electrodes to directly contact and short-circuit, etc.;
03) Internal short circuit or micro short circuit of the battery, such as improper placement of the positive and negative electrodes causing the electrodes to short-circuit, or the positive electrode to contact, etc.
57.What are the possible reasons for zero voltage or low voltage in the battery pack?
01) Is the single battery at zero voltage?
02) The plug is short-circuited or disconnected, or the connection with the plug is not good;
03) The lead wire and battery are desoldering or poorly soldered;
04) Incorrect internal connection of the battery, welding leakage, cold welding, desoldering between the connecting piece and the battery, etc.
05) The internal electronic components of the battery are not connected correctly and are damaged.
58.What are the control methods to prevent battery overcharging?
In order to prevent the battery from being overcharged, the charging endpoint needs to be controlled. When the battery is fully charged, there will be some special information that can be used to determine whether the charging has reached the end point. Generally, there are six ways to prevent the battery from being overcharged:
01) Peak voltage control: Determine the end point of charging by detecting the peak voltage of the battery;
02) dT/dt control: Determine the end point of charging by detecting the rate of change of battery peak temperature;
03) △T control: When the battery is fully charged, the difference between the temperature and the ambient temperature will reach the maximum;
04) -△V control: When the battery is fully charged and reaches a peak voltage, the voltage will drop to a certain value;
05) Timing control: Control the charging endpoint by setting a certain charging time. Generally, the time required to charge to 130% of the nominal capacity is set;
59.What are the possible reasons why a battery or battery pack cannot be charged?
01) The battery has zero voltage or there is a zero voltage battery in the battery pack;
02) The battery pack is connected incorrectly, and the internal electronic components and protection circuits are abnormal;
03) Charging equipment failure, no output current;
04) External factors cause the charging efficiency to be too low (such as extremely low or extremely high temperature).
60.What are the possible reasons why batteries or battery packs cannot discharge?
01) The battery life decreases after storage and use;
02) Insufficient charging or no charging;
03) The ambient temperature is too low;
04) The discharge efficiency is low. For example, when discharging with a large current, the diffusion speed of the internal substances of ordinary batteries cannot keep up with the reaction speed, causing the voltage to drop sharply and unable to discharge electricity.
61.What are the possible reasons for the short discharge time of batteries and battery packs?
01) The battery is not fully charged, such as insufficient charging time, low charging efficiency, etc.
02) The discharge current is too large, which reduces the discharge efficiency and shortens the discharge time;
03) The ambient temperature is too low when the battery is discharging, and the discharge efficiency decreases;
62.What is overcharging and what impact does it have on battery performance?
Overcharging refers to the act of continuing to charge a battery after it has been fully charged through a certain charging process. For Ni-MH batteries, overcharging produces the following reactions:
Positive electrode: 4OH- - 4e → 2H2O + O2↑; ①
Negative electrode: 2H2 + O2 → 2H2O ②
Due to the fact that the capacity of the negative electrode is higher than that of the positive electrode during design, the oxygen generated by the positive electrode passes through the separator and combines with the hydrogen generated by the negative electrode. Therefore, under normal conditions, the internal pressure of the battery will not significantly increase. However, if the charging current is too high or the charging time is too long, the generated oxygen may not be consumed in time, which could lead to an increase in internal pressure, battery deformation, leakage, and other undesirable phenomena. At the same time, its electrical performance will also significantly decrease.
63.What is over-discharge and what impact does it have on battery performance?
When the battery has discharged all the electricity stored inside and the voltage reaches a certain value, continuing to discharge will cause over-discharge. The discharge cut-off voltage is usually determined according to the discharge current. 0.2C-2C discharge is generally set at 1.0V/cell, and 3C or above, such as 5C or 10C, is set at 0.8V/cell. Over-discharge of the battery may have catastrophic consequences for the battery, especially high-current over-discharge or repeated over-discharge, which has a greater impact on the battery. Generally speaking, over-discharge will increase the internal pressure of the battery, damage the reversibility of the positive and negative active materials, and even charging can only partially restore it, and the capacity will also be significantly attenuated.
64.What is the main cause of rechargeable battery swelling?
01) The battery protection circuit is defective;
02) The battery has no protection function and the cell expands;
03) The charger has poor performance and the charging current is too large, causing the battery to swell;
04) The battery is continuously overcharged at a high rate and with a large current;
05) The battery is forced to be over-discharged;
06) Problems with the design of the battery itself.
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