Knowledge about lead-acid batteries

Batteries are the bottleneck of electric vehicles, the bulk of manufacturing costs, and the source of dealers' financial resources. Proper use and maintenance can greatly reduce the operating cost of electric vehicles for users, increase reputation for dealers, and reduce trouble. It is very necessary to master the knowledge of lead-acid batteries.A rough explanation of commonly used terms (approximate explanation for the convenience of non-professionals. The accurate explanation should be based on the "leadAccumulatorTechnology "ISBN7-111-09609-6/TM.929 shall prevail) First, the capacity type capacity is the amount of electricity that can be released when a fully charged battery is discharged to a prescribed termination voltage under certain discharge conditions. It is not easy to test whether it is so-called completely full. For open batteries, the specific gravity of sulfuric acid can be determined. For sealed batteries, it can only be roughly estimated by testing other indicators. The so-called termination voltage, for a 12V battery, generally refers to 10.5V. This voltage must be measured quickly, because after stopping the discharge, it will rise. Capacity is usually expressed in ampere-hour (Ah) or watt-hour (Wh), with the former being the most common. For example, 17AH, 32AH multiplied by its rated voltage is the latter representation method, such as a common 12V 12AH battery is 144WH. The capacity is often represented by a capital C. The charge and discharge rate is usually expressed in C or hour h. For example, the 10-hour rate can be expressed as 0.1C, and for a 12AH battery it is 1.2A; for example, the 20-hour rate can be expressed as 0.05C, or for a 12AH battery, it is 0.6A. There are many factors that affect the capacity. As long as the temperature decreases, the capacity decreases, and the temperature increases, the capacity increases. Also, different discharge rates, different methods of discharge, the displayed capacity is also different. There are many ways to express battery life. For electric vehicles, it can be expressed in terms of years and months, as well as continuous kilometers, and the number of full charge and discharge cycles. In more scientific terms, the end of life generally means that when the capacity drops to one-half of the root sign, which is 70%, the battery can actually be used at this time. Battery life is related to many conditions. It is enough to master the following aspects: 1. In terms of charging, the charging current is about 0.1C, and the balanced charging is the best. Regular float charging is better than cycling, and replenishing distilled water in time. 2. In terms of discharge, the discharge rate will seriously affect the lifespan. Although 0.1C is ideal, it is not realistic for electric vehicles. Try to control it at a rate of 3-5 hours, which is less than 0.5C. In short, shallow discharge (electricity) and frequent charging (electricity) can extend the battery life. 3. In terms of maintenance, it is mainly to add distilled water, add it once every two months in summer, such as 12AH battery, each interval is about 8-12ml, and do not add it in winter. If there is a lot of water loss, it may be that the charger voltage is high and needs to be corrected. In addition, the lead-acid battery has a negative temperature coefficient. In summer or when the temperature is high, the float voltage should be appropriately reduced. Shock absorption for the on-board battery of an electric vehicle also helps to extend its life and reduce operating costs.pay attentioncarMotorcycleAccessoriesRialto vendors sell distilled water and dilute sulfuric acid, just pour a little on the ground. The supplementary water is supplementary distilled water instead of dilute sulfuric acid. If you can't buy distilled water, you can use a pressure cooker to make your own. Insert one end of a 15-meter plastic tube into the exhaust valve, soak it in cold water in a circle to cool, and the other end will produce distilled water. Second, there are national standards for the classification of lead-acid batteries, as long as the following characteristics are mastered 1. Dry-charged batteries are generally open batteries. When transporting (Tran Sport) storage, no sulfuric acid is added, and supporting dilute sulfuric acid is added during use ( Some are called undiluted solution), and the electricity will be ready for use in a while. In order to prolong the service life, it is best to charge it with 0.1C current for 5-6 hours before use. 2. Valve-controlled batteries are sealed batteries. Electric vehicles are used most often. Although the sealing can also add water, some manufacturers, such as Tianneng, have considered supplementary water during manufacturing. It is very convenient to remove. Most sealed batteries must be opened and cooked. It can make perfect. What needs to be explained is that after maintenance, reinstall it and try to keep it sealed. 3. The batteries used in general automobiles can be used in electric tricycles, and the capacity should be larger. 4. The brand-name maintenance-free battery used for second-hand UPS is also a good cheap battery for electric vehicles. These batteries consume very little active material due to the plate, and have high utilization value. Most of the problems are vulcanization and water shortage caused by storage. After maintenance, most of the capacity can be restored to more than 80%. Third, the basic charging methods for chargers include constant current charging and constant voltage charging. Constant current charging uses a constant current charge. The advantage is that it will not overcurrent and can be fully charged. The disadvantage is that if you forget to power off later, it is easy to overcharge and lose. Water; Constant voltage charging is to charge with a constant voltage. The advantage is that as the charging time increases, the charging current gradually decreases. If you forget to manage it, the battery will not be damaged. The disadvantage is that the current may be large when the battery is charged with more discharge. It is easy to cause damage to the charger and deformation of the battery plate. The most common charger combines the advantages of the first two, which is the so-called current-limiting and constant-voltage type. When this kind of charger starts charging, it is in a current-limiting and unregulated state. According to the charging current and the battery terminal voltage, it is switched to the constant voltage mode at an appropriate time. Even when the battery with a lot of discharge starts to charge, due to the current limiting circuit, the current will not be very large. As the charging time increases, the charging current gradually decreases, and to a certain extent, it is converted to constant voltage charging (some manuals call it to switch to floating). Charge). This method can be divided into two-stage and three-stage. Based on this, there is the so-called smart negative pulse charger, which is actually in the high current current limiting stage. Every second, the battery is short-circuited for 1-2 milliseconds, and the battery is short-circuited for 1-2 milliseconds. ) Ability to cool the electrode plate, which is beneficial to reduce the vulcanization of the electrode plate. In addition, the supplementary charging method that is converted to constant voltage charging in the later stage of charging is changed to the constant voltage pulse widening supplementary charging method, and so on, there are many kinds of chargers. It needs to be pointed out that for series-charged chargers, some are called smart, but they are just exaggerating the publicity. In fact, they are the above content. Their disadvantage is that they cannot identify the quality of each battery in the series, especially non-brand-name batteries. , The common problem is poor consistency. Whether the charger works in current limiting or constant voltage mode is determined by testing the total series voltage instead of the specific terminal voltage of each battery. When the performance of one of them deteriorates, it will accelerate the damage of the other two due to misjudgment (either overcharge or undercharge or even reverse polarity). The best method is equalizing charging. The equalizing charging mentioned here is to charge each battery independently. For example, for a 36-volt battery, three 12-volt batteries are used in series. Use three laptop second-hand power supplies to transform into three 13.5V-13.9V chargers and charge three batteries at the same time (that is, plug in and charge without riding a bicycle), which can extend the battery life several times. Fourth, commonly used tools 1, digital voltmeter.It’s more accurate than the analog voltmeter.ChargerThe voltage is especially important. For example, when using a second-hand laptop power supply to transform into a 13.5V-13.9V charger, it is easy to cause insufficient charging, and high voltage is likely to cause overcharging and water loss. Adjust the charger with temperature compensation, and more Is inseparable. There is only one thing to note, the battery of the digital voltmeter will affect the test accuracy when its voltage drops too much, so pay attention to frequently replace the battery. 2. Fuel gauge. A fuel gauge is needed to measure the capacity of a battery. A professional fuel gauge is more expensive and is a timing constant current discharger. There is a tens of yuan electricity meter on the market (Rialto), which can also be estimated. Its essence is to judge the quality and capacity of the battery by measuring the internal resistance of the battery.The structure is very simple, that is, a voltmeter is connected in parallel with a high power with a small resistance.resistance.One more importedswitch, The switch controls the connection and disconnection of the resistance. In the specific test, first measure the open circuit voltage of the battery (that is, without connecting the resistor), and then connect the resistor in parallel for a few seconds (less than 10 seconds). At this time, the voltage will drop and the pointer will fall into one of the red, green and yellow areas. Obviously, the higher the voltage, the smaller the internal resistance and the larger the capacity. There is also an electricity meter that uses integrals made by a single-chip microcomputer, and the price is about 100 yuan. A simpler way is to use a 36 volt 100 watt incandescent light bulb (the hardware is sold for 1-2 yuan each) to discharge the battery, and judge the capacity according to the discharge time. Although the discharge current is not constant and the voltage must be continuously measured, it is a simple, effective and intuitive method after all. 3. Hydrometer. The purpose is to measure the specific gravity of sulfuric acid, and can also be used as a straw to conveniently add acid and absorb excess dilute sulfuric acid. 4. High-power charger. Generally, the electric vehicle charger is a switching power supply type, which has the advantage of saving electricity, but the disadvantage is that the current is small, generally only about 2A. The maintenance department must have a high-power charger. In terms of cost-effectiveness, it is recommended to use a smart charger composed of a tapped ring transformer, bridge rectifier and control board. The price is about 130 yuan and can provide 30A charging current. . Purpose: To charge large-capacity batteries, repair batteries, perform a full charge on batteries that are regularly floated over a period of time, and ablate batteries with slight short-circuited crystal branches. Of course, paid charging services can also be provided. 5. Lead-acid battery repairer. The main purpose is to restore the battery that has been left for too long and not charged in time. Generally, it takes a day to several weeks to charge with a constant current of 0.1C-0.05C after adding water. Using pulse repair can improve efficiency. It should be noted that the repairer only has a significant effect on vulcanization, and has no effect on the softening of the plates, the loss of active materials, and the connection of poles.