Questions and Answers on Special Maintenance Knowledge for Electric Vehicle Battery (2)

An electric car user in Inner Mongolia asked: What battery is better? Answer: At present, there are many types of batteries used in electric bicycles.In addition to the most used valve-controlled sealed lead acidAccumulatorIn addition, there are nickel-metal hydride batteries, nickel-cadmium batteries, lithium-ion batteries, polymer lithium batteries, zinc-air batteries, fuel cells, and so on. Among them, lead-acid batteries are the most numerous. Lead-acid batteries have the lowest price and are the most commonly used. China is the largest producer of lead-acid batteries in the world (Mondi). It contains less contaminated components and has good recyclability. The disadvantage is that it is smaller than the volume. In other words, under the same capacity, the weight and volume of the battery are large. The current lead-acid batteries are basically developed from floating-charge batteries. Floating charge batteries are not suitable for fast charging and high current discharge. Although technicians have spent a lot of effort to make effective improvements and can be put into practical use, their lifespan is still very unsatisfactory. The specific capacity of nickel-hydrogen battery is much better than that of lead-acid battery, the life of single battery is also better, and its high-current charging and discharging characteristics are also better than that of lead-acid battery. The problem is that there are many management problems in the series connection of nickel-metal hydride batteries. Once overcharge occurs, the problem of melting of the single battery separator will occur, which will cause the entire battery to quickly fail. Therefore, the key technical problem of domestic nickel-hydrogen batteries is still the problem of charger and battery management system, and this problem has not attracted enough attention from various battery manufacturers and car manufacturers. Therefore, the development of nickel-metal hydride batteries has been greatly restricted. The high-current and high-current characteristics of nickel-cadmium batteries are better than those of nickel-metal hydride batteries, and their anti-overcharge characteristics are also better than those of nickel-metal hydride batteries. China is also a major producer of nickel-cadmium batteries in the world (Mondi). Some people have raised the issue of cadmium pollution. China is still exporting a large number of nickel-cadmium batteries and their application products to Europe. Europe only began to restrict it in 2006. According to news broadcast by CCTV, Shenzhou No. 5 still uses nickel-cadmium batteries. This is the advantage of its relatively high reliability, so that this type of battery is still used in aerospace equipment. In this way, whether there is some over-excitation in the early withdrawal of nickel-cadmium batteries from the application of electric bicycles. The cost of nickel-cadmium batteries and the cost of chargers are significantly lower than that of nickel-metal hydride batteries. As long as the recycling process is completed, this battery type should be retained. The specific capacity of lithium-ion batteries is better than that of nickel-metal hydride batteries. For lead-acid batteries of the same capacity, the weight of lithium-ion batteries is equivalent to a laptop, so that both the elderly and the weak can use them. Its lifespan can also be better than NiMH batteries. The current mobile phone batteries basically use this kind of battery. The internal resistance of lithium batteries is relatively large. When using an electric bicycle, it will feel that the power of the car is insufficient when the battery is about to be completely discharged. The main problem of lithium-ion batteries is that the battery will explode in overcharge and overdischarge states. Cell phone batteries are all single cells that are used together with a good protection circuit, which basically eliminates the problem of battery explosion. For use on electric bicycles, a series-connected battery pack must be used, and the complexity of the protection circuit of the series-connected battery pack far exceeds that of the single battery, and the material cost is also greatly increased. At present, the cost of a good lithium battery protection circuit and the cost of a lithium battery are close to the price of the battery itself. The explosive lethality of polymer lithium batteries is lower than that of lithium ion batteries, but there is also the possibility of explosion and combustion. This is the same problem as lithium-ion batteries. Zinc-air battery is famous for its large specific capacity and low pollution. The battery adopts the method of battery replacement to update the battery zinc plate. It can be used from 160 kilometers to 220 kilometers with one replacement of the zinc sheet. Shanghai has taken the lead in developing the application of zinc-air batteries in electric bicycles in the country, and has set up dozens of power grid exchange points throughout the city, creating a precedent for the application of zinc-air batteries in electric bicycles. Its limitation is that it is temporarily unable to carry out application tests outside of Shanghai, and its use cost is also several times that of lead-acid batteries. If the scope of application is further expanded, there is the possibility of further reducing the cost of use. A dealer in Shanxi asked: Are lead-acid batteries also classified? How many types are currently divided into? What are their characteristics? Answer: The lead-acid batteries used on electric bicycles mainly include: high-capacity power-type valve-regulated sealed lead-acid batteries and gel batteries. Famous domestic brands include Shenyang Panasonic, Shanghai Haibao, Zhejiang Tianneng and Chaowei, and colloidal batteries include Huafu. The battery coverage (Guy) of these battery manufacturers is relatively wide. Shenyang Panasonic's battery uses 11 plates, the initial capacity is not large, but the life is relatively long. Haibao uses 17 plates to take into account the initial capacity and lifespan, while Tianneng and Chaowei have the largest initial capacity and their lifespan is not as good as the former. Then there is the specific gravity of sulfuric acid, Panasonic is the lowest, Haibao is the second, and Tianneng and Chaowei are the highest. The initial capacity of the battery with low sulfuric acid specific gravity is not good, but the life is better, while the high sulfuric acid specific gravity is just the opposite. In view of the lack or lack of battery inspection capabilities in some car manufacturers, the battery is tested by a "circling" method to test the battery capacity. Such inspection methods have caused some small battery manufacturers to improperly increase the specific gravity of the sulfuric acid of the battery and increase the amount of active material on the positive electrode plate (resulting in insufficient negative electrode transition of the battery and large water loss). Even take the method of reducing the number of plates to reduce costs. Such batteries do not have a long life, and such batteries are commonly found in scooters. And such scooters equipped with such batteries are also exported, giving a bad impression of Chinese products on the international market (Rialto). Mr. Wang from Liaoning asked: What is the capacity of the battery? Answer: The battery usage conditions are different, and the capacity that the battery can discharge is also different. In order to calibrate the capacity of the battery, the rated capacity of the battery is defined. The rated capacity is the minimum amount of electricity that the battery should discharge under certain discharge conditions when the battery is manufactured, and the unit is Ah (Ampere hour).The specified battery discharge conditions are: the current of the battery discharge, which is generally the discharge rate; the end voltage of the discharge, the discharge current is different, the end discharge voltage is also different; the discharge temperature, the battery is discharged when the temperature is low.capacitanceThe amount is small, and the discharge capacity is large at high temperature. In order to unify the discharge capacity, the discharge temperature is specified. The discharge rate refers to the size of the battery discharge current, namely the time rate and the current rate. The discharge time rate refers to the length of time from discharge to the final voltage under certain discharge conditions. According to the IEC standard, the discharge rates are 20 hour rate (20Hr), 10 hour rate (10Hr), 5 hour rate (5Hr), 3 hour rate (3Hr), 2 hour rate (2Hr), 1 hour rate (1Hr), 0.5 hour rate (0.5Hr) and so on. As the battery discharges, the terminal voltage of the battery will gradually decrease. The lowest voltage that can be recharged and used after being discharged at 25°C is called the end-of-discharge voltage. The discharge rate is different, the discharge end voltage is also different. Generally, the termination voltage of discharge at a rate of 10 hours is 1.8V/cell, and the termination voltage of discharge at a rate of 2 hours is generally 1.75V/cell. Below this voltage, although a little more electricity can be discharged, it is easy to cause a decrease in the capacity for recharging, so unless special circumstances do not discharge below this voltage. The rated capacity of the battery is represented by C, and the battery capacity obtained by different discharge rates will be different. For example, the current value represented by the discharge current of 10 hours rate is: I10=C10/10=0.1C10, the discharge current of 2 hours discharge rate Represents the current value: I2=C2/2=0.5C2, and the discharge current of the 1-hour discharge rate represents the current value: I1=C1/1=1C2. Manager Bai of an electric vehicle store in Hunan asked: What is the impact of battery discharge current on battery capacity? Answer: The discharge current of the battery is different, and the capacity that can be discharged is also different. The greater the discharge current, the smaller the amount of electricity that can be discharged. For example, the current commonly used in electric bicycles is 5A, and the battery with a nominal 10Ah is discharged at a rate of 2 hours. If a 10-hour rate discharge is used, it can reach 12Ah. In this way, if the battery is rated at a 2-hour rate, it should be 10Ah, and if it is rated at a 10-hour rate, it should be 12Ah. Therefore, the capacity of the battery depends not only on the capacity of the battery, but also on the discharge rate of the battery. The battery of an electric bicycle is often labeled as 10Ah (2Hr), and the same battery can also be labeled as 12Ah (10Hr) and 14Ah (20Hr). Another example. A 14Ah (2Hr) battery can also be marked as 17Ah (10Hr). There are also some batteries whose capacity is marked as a 20-hour rate. The nominal value of the battery capacity is larger, but the battery capacity has not changed significantly. Ms. Zhang from Beijing asked: Is the battery life related to discharge? Answer: Generally speaking, the greater the discharge current, the shorter the battery life; the deeper the depth of discharge, the shorter the battery life. Lead-acid batteries can cope with high-current discharge in a short time, and the depth of discharge is not deep at this time. Small current discharge, even if the depth of discharge is slightly deeper, the life of the battery battery will not have much impact. Most afraid of continuous high current discharge and deep discharge. Therefore, the nominal 17Ah battery is used for the electric motorcycle, and the discharge current of the electric motorcycle is generally 10A～17A at a speed of 35 kilometers per hour, which is about 1C, so the discharge current is relatively large. Such batteries not only have to decrease in capacity, but also have a relatively short service life. In addition, most users of electric motorcycles require longer driving ability than electric bicycles, so the depth of discharge of electric motorcycles is relatively deeper.And the speed of electric motorcycles should be faster, sobrakeAnd start acceleration should be more frequent, which consumes more battery. Therefore, the actual service life of the battery of an electric motorcycle is generally 3 to 6 months.