Causes and maintenance of problems with electric vehicle batteries

As long as it is a lead-acid battery, it will be vulcanized during use, but lead-acid batteries in other fields have a longer life than lead-acid batteries used on electric bicycles. This is because lead-acid batteries for electric bicycles have a more easily vulcanized. Work environment.

The cause of the problem with the electric car battery

1.1 caused by the battery itself

Why do you say this! We know the working principle of lead-acid batteries. The process of charging and discharging lead-acid batteries is the process of electrochemical reaction. When charging, lead sulfate forms lead oxide, and lead oxide is reduced to lead sulfate when discharged. Lead sulfate is a substance that is very easy to crystallize. When the concentration of lead sulfate in the electrolytic solution in the battery is too high or the static idle time is too long, it will "carry" into a group and form small crystals. These small crystals will attract the surrounding area. The lead sulfate, like a snowball, forms a large inert crystal. When the lead sulfate is crystallized, it cannot be reduced to lead oxide, but also precipitates on the electrode plate, causing the working area of the electrode plate to decrease. This phenomenon is called vulcanization. At this time, the battery capacity will gradually decrease until it is unusable. When the lead sulfate is piled up in a large amount, lead particles are attracted to form lead branches, and the lead bridge between the positive and negative plates causes a short circuit of the battery. If there is a gap in the surface of the plate or the sealed molded case, lead sulfate crystals will accumulate in these gaps and cause expansion tension, which eventually causes the plate to break off or the outer casing to rupture, resulting in irreparable physical damage to the battery. Therefore, the main mechanism leading to failure and damage of lead-acid batteries is that the battery itself cannot avoid vulcanization.

1.2 reasons for battery production

Various battery manufacturers have adopted various methods for the particularity of lead-acid batteries for electric bicycles. The most typical method is as follows:

1 Increase the number of plates.

The original design of the single-frame 5-piece 6-piece system was changed to 6-piece 7-piece system, 7-piece 8-piece system, and even 8-piece 9-piece system. Increase the battery capacity by reducing the thickness of the plates and the spacers and increasing the number of plates.

2 increase the specific gravity of the battery sulfuric acid.

The original sulfuric acid of the floating battery is generally between 1.21 and 1.28, and the sulfuric acid specific gravity of the battery of the electric bicycle is generally about 1.36 to 1.38, which can provide a larger current and increase the initial capacity of the battery.

3 Increase the amount and proportion of lead oxide active material active material.

Increasing lead oxide increases the electrochemical reaction species involved in the discharge, which increases the discharge time and increases the battery capacity.

Through these measures, the initial capacity of the battery satisfies the capacity requirements of the electric bicycle, and in particular, the characteristics of the large current discharge of the battery are improved. However, as the number of plates increases, the capacity of sulfuric acid decreases, and the battery heat causes a large amount of water loss. At the same time, the probability of micro-short circuit and lead-bridge bridging of the battery increases. Increasing the specific gravity of the sulfuric acid increases the initial capacity of the battery, but the vulcanization phenomenon is more serious. One of the most basic principles of sealed batteries is that after the positive electrode plate is deoxidized, the oxygen directly goes to the negative plate and is absorbed by the negative plate to be reduced to water. The parameter of the technical index of the battery is called "sealing reaction efficiency". This phenomenon is called "oxygen cycle". In this way, the battery has little water loss, achieving "maintenance-free", that is, no water is added. For this reason, it is required that the capacity of the negative electrode plate is made larger than that of the positive electrode plate, which is also called a negative electrode transition. Increasing the active material of the positive electrode plate inevitably reduces the transition of the negative electrode, the oxygen cycle becomes worse, the water loss increases, and the vulcanization is caused. Although these measures increase the initial capacity of the battery, they cause water loss and vulcanization, while dehydration and vulcanization contribute to each other, and the end result is to sacrifice the life of the battery.

4 There is also the problem of the virtual group loading of the welding.

The place where the virtual welding is easy to occur is the plate. Each cell has 15 plates, which are 15 solder joints. One battery has 6 cells, and there are 90 solder joints. One battery consists of 3 12V batteries, and there are 270 solder joints. . If there is a virtual solder joint in the solder joint, the capacity of the single cell decreases, and the cell forms a backward battery, causing the entire battery is behind, and the battery will form a serious imbalance, which causes the battery to fail prematurely. Even if the virtual soldering control is in the first ten thousandth, there will be a set of batteries in each of the 37 batteries. There is absolutely no soldering, which is absolutely not allowed. The lead-calcium alloy grid cells will precipitate calcium during soldering to mask the problem of solder joints. As a result, many battery manufacturers prefer to use low-ruthenium alloy grids instead of lead-calcium alloys. The low-antimony alloy grid has a lower oxygen evolution and hydrogen evolution voltage, a larger battery output, a relatively serious water loss, and a battery that is more susceptible to vulcanization.

From the above we can see: Why the battery is good or bad, and some manufacturers grow the battery life will be longer under the same conditions of use.

1.3 Causes of the use environment of electric vehicles themselves

As long as it is a lead-acid battery, it will be vulcanized during use, but lead-acid batteries in other fields have a longer life than lead-acid batteries used on electric bicycles. This is because lead-acid batteries for electric bicycles have a more easily vulcanized. Work environment.

1 deep discharge

The lead storage battery used in the car is only discharged in one direction during ignition. After ignition, the generator will automatically charge the battery without causing deep discharge of the battery. Electric bicycles are not likely to be charged when riding, and often exceed 60% of deep discharge, when deep discharge, the concentration of lead sulfate increases, and the vulcanization is quite serious.

2 large current discharging

The 20km cruise current of an electric car is generally 4A, which is higher than the battery operating current in other fields, and the speeding overloaded electric vehicle has a larger operating current. Battery manufacturers have performed a cycle life test of 70% for 1C charging and 60% for 2C discharge. After such a life test, there are many batteries that can reach 350 cycles of charge and discharge cycles, but the actual use effect is far from the same. This is because high current operation increases the depth of discharge by 50% and the battery accelerates vulcanization. Therefore, the battery life of the electric motorcycle is shorter, because the body of the electric motorcycle is too heavy, the motor power is large, and the working current reaches 8A or more during cruise. Some even reach 10A.

3 high charging and discharging frequency

The battery used in the backup power supply field will only be discharged when the power is cut off. If it is stopped 8 times a year, it will reach 10 years of life, only 80 cycles of charging life, and one year of electric vehicle charging and discharging cycle 300. More than a few times are very common. Some people may charge it several times a day, and the charging time is very short. It is used without being full.

4 short charge

Since the electric bicycle is a vehicle, the charging time is not much. It is necessary to complete the charging of 36 volts or 48 volts in 20 hours in 8 hours. This requires an increase in the charging voltage (usually a single section of 2.7 to 2.9 volts) when charging. When the voltage exceeds the oxygen evolution voltage (2.35 volts) or the hydrogen evolution voltage (2.42 volts) of a single cell, the battery will open and vent due to excessive oxygen evolution, causing water loss, increasing the electrolyte concentration, and aggravating the vulcanization of the battery. ......

5 Cannot be charged in time after discharge

As a means of transportation, the charging and discharging of the electric bicycle are completely separated, and it is difficult to conditionally charge in time after discharging, and if a large amount of lead sulfate formed after the discharge is not charged and reduced to lead oxide for more than half an hour, the crystal will be vulcanized.

1.4 Reasons for the production of electric bicycles

Most car controllers .html"target="_blank"> controllers have a speed limit plug, and some car manufacturer simply remove the speed limiter from the factory, which can attract customers who value speed and reduce costs. The current is very high at high speeds, which can seriously shorten the battery life.

The minimum protection voltage of a 12V lead-acid battery is 10.5V. If it is a 36V battery pack, the minimum reserve voltage is 31.5V. Currently, most controllers use the controller .html"target="_blank">the controller under voltage protection voltage is also It is 31.5V. On the surface, this is correct. However, when the voltage of the 36V battery pack is only 31.5V, due to the poor capacity of the battery, there will definitely be a battery voltage lower than 10.5V. Discharge state. At this time, the battery capacity of over discharge drops sharply. At this time, the damage to the battery is not only the single battery, but the life of the entire battery. In fact, the battery voltage is lower than 32V until 27V. The added capacity is less than 2 kilometers, but the damage to the battery is very large. As long as this happens 10 times, the battery capacity will be less than 70% of the nominal capacity. In addition, some users found that the battery is After the under voltage, after 10 minutes, the battery is not under pressure, and then take the power to drive, which is more damage to the battery, and most of the car's manual does not give the user a warning. Currently most controllers .html"target= "_ Blank">. The controller has adjustable potentiometers inside, and the vibration drift of this adjustable potentiometer is more serious. In the price competition, in the face of the user group that pays more attention to the appearance of the car, few products use precision multi-turn potentiometers that resist vibration. It is not surprising that such controllers drift after vibration.

1.5 Reasons for charging equipment

One word widely circulated in the industry is that the battery is not worn out, but is burnt. In order to meet the short-time high-capacity charging of the electric bicycle battery, in the three-stage constant voltage current limiting charging, it is necessary to increase the constant voltage value to 2.47V to 2.49V. Thus, the oxygen evolution voltage of the positive electrode plate of the battery and the hydrogen evolution voltage of the negative electrode plate are greatly exceeded. In order to reduce the charging time, some charger manufacturers' products have increased the current of the constant voltage to float charging, so that after the charging indication is fully charged, it is not fully charged, and it is compensated by raising the floating charging voltage. Thus, the float voltage of many chargers exceeds the single cell voltage of 2.35V, so that a large amount of oxygen is still being evolved during the floating charge phase. The oxygen circulation of the battery is not good, so that it is continuously exhausted during the floating charge phase. The constant voltage value is high, which guarantees the charging time, but the sacrifice is water loss and vulcanization. The constant voltage value is low, and the charging time and charging power are difficult to guarantee. On the basis of improving the battery grid alloy of the battery, improving the gassing potential, improving the oxygen cycle performance, and improving the efficiency of the sealing reaction, the maximum charging voltage for controlling charging is below 2.42V, that is, below the hydrogen evolution potential. This will inevitably lead to an increase in charging time. This requires the addition of a depolarized negative pulse in the state of high current charging (current limiting charging) to improve the charging acceptance of the battery and to charge more when charging at a high current. Some power, shorten the charging time. 70% of the 2C current is charged, when the battery is relatively large in charging capacity, the battery is charged with a large current, and the damage to the battery is relatively small. The battery is basically no higher than the severe hydrogen evolution voltage. Once above the hydrogen evolution voltage, the battery will quickly lose water. To use such a charger, continuous charging and discharging must be used. If the charging is stopped for a few days, the battery will be severely vulcanized and will fail prematurely. When the user uses the battery, it is impossible to guarantee that it can be charged in time after each use. If the battery is not charged in time within a year, the vulcanization of the battery will accumulate. Some charger manufacturers exaggerate certain features, and the finished product is not as good as its promotion.

1.6 Other reasons

Many batteries can get better results in the single test. However, for tandem battery packs, the difference is due to the difference in capacity, open circuit voltage, state of charge, and degree of vulcanization. The monomer that is enlarged and has a poor state affects the entire battery, and its life is significantly reduced.

From the charging of the battery on the production line to the use of the car after the user purchases the car, there are many links, and the interval may even last for several months. During this period, due to the lack of recharging of the battery, the self-discharge produces a large amount of lead sulfate. Stacking crystals, the new battery that the user just bought may be a battery that has been aging or even reported.

When the battery manufacturer performs the warranty, the battery is not completely eliminated. After the battery is returned, the battery manufacturer re-inspects the charge and discharge. In the inspection, it is often found that more than 60% of the single cells are batteries that do not meet the return conditions. The reason is that in the series battery pack, the individual batteries fall behind to form a whole group of batteries, and the whole group returns. Many battery manufacturers have re-supplied, hydrated, desulfurization, and packaged the returned battery to provide users with the opportunity to improve the effective service life of the battery, reduce the scrap rate, and reduce the loss of partial claims of the battery manufacturer. Therefore, many dealers have already felt that the battery provided by the manufacturer is obviously "a generation is not as good as a generation."

2 Electric car battery maintenance

The electric vehicle battery will be replaced with a new one for a year and a half. How can we extend the battery life of the electric vehicle?

(1) First of all, you can't overload the overweight (such as riding a bicycle or carrying heavy loads, etc.)

When driving, it is found that the meter shows that the battery is running low, because the deep discharge has a great loss of battery life.

(2) Pay attention to the charging method

When the new battery is charged for the first time, the time must be long. Make sure that the power is sufficient. For lead-acid batteries, regardless of the distance, you should charge immediately after use, do not think that the battery is completely exhausted before you think about charging. If the car is not used for a long time, you must also replenish it once a month. This protects the battery and extends its life.

(3) Try to avoid sudden braking

Frequent sudden braking will affect the brakes and the battery capacity; the speed should not be too fast, the faster the speed, the greater the loss of the battery.

(4) Do not use the motor to start the car directly in a static state. It is best to use the foot to assist the start.

When driving on the bridge, uphill, or against the wind, be sure to use the pedal boost to avoid impact damage to the battery and affect the battery's continued mileage and service life.

(5) Maintenance of electric vehicle battery during use

a) When starting, climbing, climbing, or driving in the wind, it should be supplemented with manpower to avoid instantaneous high-current discharge.

b) When acceleration is required, the speed control should be rotated slowly to avoid direct acceleration to the fastest gear.

c) If the road conditions permit, the electric car can be driven at the highest speed.

d) Try to avoid frequent braking and starting, and use the ankle drive when the road is crowded.

e) The battery indicates that the battery is dead. After a while, you will find that the battery has a small amount of voltage, called the rebound voltage. Users should avoid using this voltage to ride.

(6) Battery maintenance for electric vehicles

a) Charging at night, the average time is about 8 hours, avoid overcharging and undercharging.

b) When charging, the indicator light should not be pulled out immediately when it is fully charged, and then float for 2-3 hours.

c) Fill the electricity as much as possible. If you really need to ride during the charging process, it should be filled immediately after the ride.

d) Diligent charging is beneficial to cycle life, but currently there are a large number of chargers on the market that have high failure rate, poor reliability, and low precision. Therefore, sometimes charging will affect the battery life. When the battery is emptied and recharged, some single cells may be over-discharged, and the over-discharge battery charging capacity will be greatly reduced, causing a problem of insufficient charging. In addition, due to the recharge of the battery, the charger has a heavy load time and is prone to damage the charger. . Therefore, it is more reasonable to perform one charge when the battery discharges 50-70% of the power, which is good for the battery life.

(7) Electric vehicle battery maintenance should pay attention to avoid loss of electricity storage

The deficient state means that the battery is not charged in time after use. Lead sulfate occurs in a depleted state, and lead sulfate crystals are attached to the electrode plates to block the ion channel, resulting in a decrease in battery capacity. The longer the idle state is idle, the more serious the battery damage. Especially in the summer, be sure to charge in time. The storage time is replenished every more than one month.

(8) Maintenance of electric vehicle battery should also be maintained in time

Maintenance is required when the battery is:

a) Long-term charging does not change green light

b) The battery is hot when charging

c) Battery capacity drops too fast

(9) Electric vehicle battery maintenance should be checked regularly

In the course of use, if the mileage of the electric vehicle suddenly drops by more than ten kilometers in a short time, it is very likely that at least one battery in the battery pack has a short circuit, such as a broken grid, softening of the plate, and falling off of the active material of the plate. . At this time, inspection, regeneration and matching should be carried out in time. This will extend battery life and maximize cost savings.

(10) Pay attention to the maintenance of electric vehicle battery: the battery should be installed firmly on the electric bicycle to prevent the battery from being damaged by vibration during riding; often remove dust and dirt from the battery cover, and keep the battery dry and clean. In case the battery is discharged by itself.

The page contains the contents of the machine translation.