This article is mainly about the related introduction of electric vehicle battery, and focuses on the detailed description of the charging problem of electric vehicle battery.

Electric vehicle batteries are the source of power for electric vehicles. The vast majority of current electric vehicles are equipped with lead-acid batteries. Lead-acid batteries are low in cost and cost-effective. Because this battery can be recharged and can be used repeatedly, it is called a "lead-acid battery". In 1860, France's Plantai invented a battery with lead as electrodes, which was the predecessor of lead-acid batteries.

There are four types of power batteries that can be used by electric bicycles, namely valve-regulated lead-acid maintenance-free batteries, colloidal lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries.

Lead-acid batteries

Lead-acid batteries are widely used and widely studied by various electric vehicles in various countries due to their low price, abundant material sources, high specific power, mature technology and manufacturing process, and high resource recovery rate. Electric bicycles have been widely accepted by people as a labor-saving, convenient, fast, comfortable, inexpensive, and zero-emission personal transportation tool, and have been valued by relevant state departments. The "Light Electric Vehicle Industry Development Strategy Research" project group participated by the Development Research Center of the State Council, the National Development and Reform Commission, the Ministry of Construction, the Ministry of Science and Technology and other ministries and commissions put forward the "Light Electric Vehicle Industry Development Strategy Research" report. The national possession of electric bicycles has reached more than 30 million. More than 95% of electric bicycles use valve-regulated lead batteries. [1]

The vast majority of commercial electric bicycles use sealed lead-acid batteries, which do not require frequent water replenishment during use and are maintenance-free. The main chemical reaction is: PbO2+2H2SO4+Pb←charge, discharge→2PbSO4+2H2O

When the lead-acid battery is charged, the spongy lead that becomes the positive and negative poles of lead sulfate releases the fixed sulfuric acid components into the electrolyte, and turns into spongy lead and lead oxide, respectively, and the concentration of sulfuric acid in the electrolyte keeps increasing; and vice versa. During discharge, the lead oxide in the anode and the spongy lead on the cathode plate react with the sulfuric acid in the electrolyte to become lead sulfate, and the concentration of sulfuric acid in the electrolyte continues to decrease. When the lead-acid battery is undercharged, the lead sulfate of the anode and cathode plates cannot be completely transformed into spongy lead and lead oxide. If the charge is insufficient for a long time, it will cause lead sulfate crystallization, sulfide the plates, and deteriorate the quality of the battery; When the battery is overcharged, the amount of oxygen produced by the anode is greater than the adsorption capacity of the cathode, which increases the internal pressure of the battery, causes gas overflow, reduces the electrolyte, and may also cause the active material to soften or fall off, and the battery life is greatly shortened.

Comprehensive performance has been greatly improved

In the past 10 years, the overall performance of valve-regulated lead batteries for electric bicycles has been greatly improved. Take the 6-DZM-10 battery as an example. In 1997, this type of battery had insufficient capacity, the 2h rate (5A) discharge capacity was less than 10Ah; the specific energy was low, and the specific energy at the 2h rate was less than 30Wh/kg; the life was short, and the cycle life at 100% discharge depth was only 50~ 60 times (before the capacity drops to 8Ah; the same below), the service life is only 3 to 5 months and other issues.

By 2003, the 2h rate (5A) discharge capacity reached 11~13Ah; the 2h rate specific energy reached 33~36Wh/kg; the cycle life of 100% discharge depth reached 250~300 times, and the service life could reach more than 12 months. The problems of valve-regulated lead-acid batteries for electric bicycles have basically been solved.

The deep cycle life performance of this type of battery has new and breakthrough progress. The main performance is: the initial discharge capacity of 2h rate (5A) reaches 14Ah; the specific energy of 2h rate reaches 38Wh/kg; the cycle life of 100% discharge depth exceeds 400 times, the total discharge capacity is 4500Ah, and the corresponding cumulative mileage is about 18000km (at 4km /Ah meter, the same below). The highest deep cycle life exceeds 600 times, the total discharge capacity is 6151Ah, and the corresponding cumulative mileage is about 24600km. If the capacity is lower than 7Ah as the end of life sign, the deep cycle life is 943 cycles, the total discharged capacity is 8710Ah, and the corresponding cumulative mileage is about 34800km. If the battery pack with a deep cycle life of 250 times or a total capacity of 2250Ah and a corresponding cumulative mileage of 9000km can be guaranteed for 1 year. [1]

Pay attention to matching with the charger

In many years of practice, electric bicycle manufacturers and battery manufacturers have gradually realized the importance of matching between the battery and the related equipment of the electric drive system, especially the matching with the charger. Manufacturing quality is the prerequisite for the quality of the battery, but only when it is used with a matching charger can the superior performance of a high-quality battery be exerted, otherwise the high-quality battery cannot fully exert its potential superior performance. [1]

Due to differences in formula, structure, acid concentration, etc., the suitable charging parameters of batteries from different manufacturers are different. For example, we found in our research that the charging parameters of batteries from different manufacturers in the constant voltage stage can differ by 1.5~2.0V (for 36V battery packs). The basic requirements for suitable charging parameters are: to ensure that the battery can be fully charged, and that the battery capacity will not be abnormally attenuated due to undercharging; and to ensure that the battery will not cause serious water loss and thermal runaway due to overcharging during the full life of the battery. [1]

Lead battery for pure electric vehicle

The early open-ended lead batteries used in pure electric vehicles adopted the research results during the "Eighth Five-Year Plan" period, and have obtained successful experience of 19 months (120,000 kilometers). The key is to accumulate the control of the charging method and the depth of discharge. , Timely replenishment and other system matching work experience and meticulous maintenance experience. In recent years, four-wheeled miniature electric vehicles (including tour buses, patrol cars, golf carts, short-distance road vehicles, etc.) have developed rapidly, and most of the cars used open-type lead batteries. The corresponding type of battery is favored by battery manufacturers. [1]

The electric vehicle adopts a new product of valve-regulated sealed lead storage battery. Its performance is: 3h rate capacity 55Ah; 3h rate specific energy is 33Wh/kg and 84Wh/L; 75% discharge depth has a cycle life of more than 400 times. It is believed that the successful experience of valve-regulated lead batteries for electric bicycles can be extended to valve-regulated lead batteries for pure electric vehicles, and the performance will be further improved. [1]

Lead-acid batteries for hybrid electric vehicles

At present, hybrid electric vehicles are basically divided into three categories: mild hybrid (that is, the electric system is mainly used for starting and recovering braking energy, and the 42V electric system that will be promoted in all cars belongs to this type), moderate hybrid (that is, electric The system is used for starting, recovering braking energy and driving in medium and short distances), heavy hybrid type (that is, the electric system is used for starting, recovering braking energy and driving for longer distances, also known as "Plug-in"). [1]

It has been made clear in domestic and foreign literature: in mild-hybrid electric vehicles, valve-regulated lead batteries have advantages, mainly due to their low cost, mature technology, and reliable performance; valve-regulated lead batteries for moderate-hybrid electric vehicles , ALABC (Advanced Lead Acid Battery Consortium) is organizing research and development, and is preparing to compete with MH-Ni batteries for the market of moderate hybrid electric vehicles. The wound bipolar battery and TMF (metallic battery) have been launched and tested on-board. Thin film) batteries; in the field of heavily hybrid electric vehicles, the specific energy of lead-acid batteries is low and cannot meet the long-distance driving requirements of electric systems. [1]

Gel battery

It is an improvement of ordinary lead-acid batteries with liquid electrolyte. It uses gel-like electrolyte with no free liquid inside. Under the same volume, it has large electrolyte capacity, large heat capacity, and strong heat dissipation ability, which can avoid the thermal runaway phenomenon that common batteries are prone to; low electrolyte concentration, weak corrosion to the electrode plate ; The concentration is uniform and there is no acid stratification.

Ni-MH battery

(Ni-MH)

Ni-MH storage battery is a rookie in the battery family that emerged in the 1990s and has developed rapidly. The electrode reaction of Ni-MH battery is:

Positive electrode: Ni(OH)2+OH-= NiOOH+H2O+e-

Negative electrode: M+H2O+e=MHab+OH-Ni(OH)2+M=NiOOH+MHab

It belongs to the same alkaline storage battery as the nickel-cadmium storage battery, but it replaces the negative electrode material cadmium cd in the nickel-cadmium storage battery with a hydrogen-absorbing alloy material (mh), and the electromotive force is still 1.32v. It has all the excellent characteristics of nickel-cadmium batteries, and the energy density is higher than that of nickel-cadmium batteries. The main advantages are: high specific energy (long distance for a single charge); high specific power, stable discharge even when working with high current (good acceleration and climbing ability); good low-temperature discharge performance; long cycle life; safe and reliable, Maintenance-free; no memory effect; there is no pollution problem to the environment, it can be regenerated and used, in line with the concept of sustainable development. However, the cost of Ni-MH batteries is too high and expensive.

Lithium Ion Battery

Lithium-ion battery is a new type of high-energy storage battery first introduced to the market by Sony in 1990. Its advantage is that it has high specific energy and is currently the battery with the highest specific energy. It has been promoted and applied in portable information products.

Lithium-ion batteries are generally considered to have the following advantages: large specific energy; high specific power; low self-discharge; no memory effect; good cycle characteristics; fast discharge and high efficiency; wide operating temperature range; no environmental pollution, etc., so It is expected to enter the ranks of the best power sources in the 21st century. It is expected that during 2006-2012, when lithium-ion batteries are further developed, the market share of MH/Ni storage batteries will shrink. Lithium-ion market share will expand. There are already sales of electric bicycle products that use lithium-ion batteries.

Driven by the development of new and inexpensive cathode materials with good safety, good cycle performance, and high specific capacity, lithium-ion batteries for electric bicycles are approaching practical use. Several companies already provide more mature lithium-ion batteries for electric bicycles equipped with battery management systems (BMS). There are also electric bicycle manufacturers specializing in the production of lithium-ion batteries. The author believes that the lithium-ion battery used in electric bicycles will be the first commercialized and large-scale power battery used in the car; it will be a large-scale practical battery after the lead battery, and it will also become a high-end electric battery. Batteries for bicycle products. There have been many reports on the trial of large-scale lithium-ion batteries on pure electric cars and electric buses, as well as on hybrid electric vehicles. According to the current level of development and experience of lithium-ion batteries, it is believed that the safety of battery packs below 48V10Ah for electric bicycles is guaranteed, but there is still a lot of hard work to be done for large-scale lithium-ion batteries to be used in commercial electric vehicles. The reasons are Mainly: pure electric cars and electric buses, as well as hybrid electric vehicles, use a large number of batteries, complex systems, more difficult safety, higher requirements for reliability and consistency, and high prices. It has been reported that Shenzhen BYD will provide 200 electric cars powered by lithium-ion batteries to form a taxi fleet in 2005, but it has now been postponed to 2007. [1]

The fuel cell

The fuel cell directly converts chemical energy into electrical energy and supplies it to an electric motor to drive the vehicle. Its main advantages are: high efficiency, can save fuel; zero emission; low noise, etc., especially suitable for vehicle power source. Hydrogen fuel cell vehicles will be ideal and eventually replace vehicles fueled by petroleum products. [1]

Zinc-nickel battery (Zn-Ni)

Zn-Ni batteries were once considered to be the batteries for electric vehicles that should be promoted. Judging from the market screening of 4 to 5 years, it has hardly been used in commercial electric vehicles. This is mainly due to the high price of Zn-Ni batteries (2.5 to 4 yuan per VAh, which is 4 to 6 times that of lead batteries); during the cycle, the initial capacity decay rate is large, which affects the actual service life of the battery pack. In addition, the rapid development and price reduction of lithium-ion batteries have made the application of Zn-Ni batteries in electric vehicles more uncompetitive. [1]

Zinc-air battery

Zinc-air battery is a kind of metal-air battery, which belongs to the category of semi-fuel cell. It has the advantages of high specific energy, abundant raw materials, low price, and no pollution. It is considered as a competitive candidate for electric vehicle batteries.

Chinese Americans once established PowerZinc in Shanghai, which produces mechanical rechargeable zinc-air batteries, and has built a demonstration workshop. Zinc-air batteries for electric bicycles and electric motorcycles manufactured by the manufacturer have been tested for mileage, reaching 150km and 250km respectively, and a lot of promotion and application work has been done. 50 battery replacement points have been established in Shanghai. But within a year, the promotion and trial work stopped, and the result of market screening was not accepted by users. Later, with the support of some leaders, an electric bus was built using the zinc-air battery as a power source. However, due to the poor high-power performance of the zinc-air battery, the starting and acceleration performance of the car was obviously poor. A lot of work has been done at home and abroad in the development of zinc-air batteries for electric vehicles. In recent years, the research and development of zinc-air batteries for electric vehicles in China has re-emerged, but practice has proved the original superiority of zinc-air batteries, and also exposed some problems that have been reported abroad, such as zinc electrode replacement service system and regeneration. Cost, life of oxygen electrode, battery electrolyte leakage, creeping leakage or overflow, etc.

The battery does not store electricity, indicating that the battery has been vulcanized or broken or short-circuited. The vulcanized battery should be repaired with a repairer. The broken or short-circuited battery needs to be manually opened and replaced by the plate. If it is a loss of electricity caused by normal use, it can be fully charged; but if the capacity is severely reduced due to severe sulfidation of the electrode plate or the lead oxide on the anode plate, it can only be scrapped. Secondly, the number of charging times of electric vehicle batteries is regulated. The new national standard GBT 18332.1-2009 stipulates that it is 400 times. When the number of cycles is reached, the battery performance will inevitably decrease, so it will lose the value of repair. Although slight vulcanization has a certain repair value, it is difficult to find in daily life, so it has no practical significance.

When the appearance of the battery is not damaged, swollen, and there is no sign of short circuit or open circuit, the following methods can be used to try to repair the battery:

1. Use positive and negative pulses to depolarize and charge the battery, and then fully discharge it. This cycle is three times. If the capacity shows signs of recovery, you can cycle several times to achieve a better repair effect.

2. Add water for repair. Deionized water or purified water must be added to the water. Do not add tap water, which will cause a big problem of battery self-discharge. The specific method is as follows:

1) Fully discharge the battery first, because the internal acid density of the battery after discharge is basically below 1.1g/mL;

2) Take out the cover sheet, and then remove the safety valve, keep it well, and don't mess up the safety valve for later use;

3) Add water. Generally, the amount of water per cell for a 12AH battery is 8-10g, and the amount of water per cell for a 20AH battery is about 15g;

4) Let stand for about one hour, and install the safety valve and cover plate;

5) Charge, fully discharge after fully charged, and repeat this cycle three times.

Repairing the battery of an electric vehicle is a very professional profession. It is necessary to master the internal structure of the battery and the principle of the battery. Not all batteries are worth refurbishing. Generally, if rehydration or recharging cycles can be used to extend the battery life, it can be repaired. Others like no voltage and no current need not be done.

1. unbalanced

Repair method: find out the capacity, voltage, self-discharge, internal resistance of the battery, etc. and use it together.

2. Water loss

Repair method: Pry open the cover above the battery. The cover of some batteries is glued with ABS glue, and some batteries are connected by buckles. Some are skateboards. Be careful not to damage the cover when you pry open the cover. At this time, the rubber caps of the 6 exhaust valves can be seen. Open the rubber cap to expose the vent hole, through the vent hole you can see the inside of the battery. The exhaust valve base of some batteries can be unscrewed, and the exhaust valve base can be unscrewed without opening the rubber exhaust valve. Some batteries have some fillers around the rubber caps. Open the cover and shine a flashlight to see if there is any dryness inside the small hole, that is, if the battery has lost water. The plates of the battery are wrapped with white glass fiber cotton, which should be moist under normal conditions. Use a dropper to suck distilled water into the battery through the vent hole. Cover the vent hole with the water-filled battery with a breathable shield to prevent dust from falling into the vent hole. It is best to use medical double distilled water. The principle of hydrating is to take less and not more. If it is not enough, it can be added. If it is too much, the proportion of acid will decrease and the battery capacity will be insufficient. Those who are inexperienced can master it by 5mL per hole.

Special reminder: Use glass or plastic straws for water replenishment tools. It is recommended to use a medical disposable syringe, which is convenient to use and convenient to measure. Do not use any metal-containing equipment as the water replenishment tool. The metal needle of the syringe should be removed and a plastic tube should be used before use.

3. Sulfation

Repair method: repair the vulcanized battery with a Kodi repair instrument, adopt fuzzy digital control theory, measure the state of the battery, continuously emit positive and negative variable frequency particle waves while charging and discharging, and take 10 to 20 hours to remove the battery Lead sulfate becomes hard after crystallization.

4. Plate softening

Repair method: After discharging the battery to 10.5V, use a bulb for deep discharge for 1-5 hours. Then use the activation instrument to activate the repair.

5. Short circuit

Repair method: water battery can be punched clearly to get out the short-circuited lead powder! Electric vehicle batteries can quickly short-circuit the positive and negative poles and burn out the short-circuited places.

6. Open

Repair method: 100A test battery voltage 0V as an open circuit, use a single measurement method to measure the open circuit and weld it. The open circuit of the battery can be measured with a multimeter.

This is the end of the related introduction about electric car batteries. If there are any deficiencies, please correct me.

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