The difference voltage between batteries in electric cars

A, The problem of electric vehicles battery

Electric bicycles develop rapidly. The actual output each year is more than social ownership in recent years, this is an amazing data, it shows that on the production and marketing of electric vehicles is experiencing the most glorious history. In this prosperous market, making money is not too difficult. However, every advantage industry has "soft rib", if you would like to ask in the fight club boss figure in the industry, what is the most headache problem of distribution of electric vehicles, the only answer is short battery life.

Most manufacturers are now promised battery warranty for a year, merchants, of course, so propaganda, but problem came out after half a year, a large number of users to come back, they are not to the secondary consumption, also is not to introduce a friend to buy cars, but to replace the battery. Even if the battery manufacturer warranty commitments, users will not be satisfied, they will think that this is the quality problem of the electric car, dealer has spent a lot of energy, still can't avoid being complaints. Perhaps the problem lies in a battery manufacturers, battery manufacturers also have intentions, however, the design of the battery and discharge cycle test show that the cycle of the battery life is indeed a year and a half or two years, when the production is in strict accordance with the process of quality control, but after six months a lot of batteries will be aging. Some manufacturer to try even with life longer solid battery, nickel batteries lithium battery instead of lead batteries, but costly in front of the market is given priority to with commuters consumers lose the competitive advantage, a lot of rich pioneering and enterprising spirit of the manufacturers have been mercilessly beat. As we all know, a lot of electronic products such as TV, computer can live for ten years, but the factory can only provide one year warranty, and the life of the electric car battery up to two years, battery manufacturers to your quality assurance for a year, it is to disguise electric vehicle battery life is not perfect the reality of the helpless, at the same time to stabilize the consumer confidence of users. This "brave" the method of quality assurance in the short term can also resist the moment, after a long time, the problem is always apparent. So, there are many guerrilla type manufacturer in the industry, they for half a year cycle, not to establish a fixed customer base, at the expense of the damage the interests of the whole industry and for their personal interests.

So how to improve the battery life, how to improve the use of the environment, and so on of cells, are you very disappointed, but concerns. In order to figure out ways to extend battery life, must first know the battery failure mechanism, so as to suit the remedy to the case.

Second, the electric car leads short battery life

From 1859, the French Gaston plante found the phenomenon of lead-acid battery, lead acid battery has always been the most widely used in the field of battery products, such as automobiles, motorcycles, ships, aircraft, have lead-acid battery back-up power supply devices, but we have heard a lot from these areas and dissatisfaction with lead-acid batteries, however, why the same products to the electric bicycle is truly "complain". Below we from several aspects in this paper, the causes of this problem.

1, the working principle of the lead-acid battery reasons

Lead-acid battery charging and discharging process is the process of electrochemical reaction, charging, lead sulfate to form lead oxide, discharging lead oxide and reduction of lead sulfate. And lead sulfate is a kind of very easy to crystalline substance, when the battery in the electrolytic solution of high concentration of lead sulfate or static idle time is too long, will be "into" ball, forming a small crystal, these small lead sulfate crystals to attract around, like snowball into larger inert crystal, crystal after charging of lead sulfate not only can't back into lead oxide, attached to the plate electrode will precipitate, cause the loss of the electrode plates work area, this phenomenon is called sulfide, is often said that aging. When the battery capacity will gradually decline, until can't use. When large Numbers of lead sulfate are piled up when will attract lead particles form of lead, lead branch bridge between positive and negative plates will cause the battery to short circuit. If there is crack plate surface or sealed plastic shell, lead sulfate crystallization within those gaps will accumulate, and expansion of tension, finally broke off the plate or shell burst, causing irreparable sex physical damage to the battery. So, the leading cause of lead-acid battery failure and damage mechanism of sulfide is the battery itself is inevitable.

2, the reason of electric bicycle special working environment

As long as it is lead-acid batteries, sulfide in the process of use, but in other fields than lead-acid battery electric bicycle on the use of lead-acid battery has a longer life, this is because the electric bicycle lead-acid battery has a sulfide work environment more easily.

1) depth of discharge

Use of lead-acid batteries in the car just one-way discharge during ignition, the ignition after generating opportunities for automatic rechargeable batteries, cause no battery deep discharge. And at the time of the ride electric bicycle can't be charging, often more than 60% of the depth of discharge, deep discharge, lead sulfate concentration increasing, the sulfide could be quite serious.

(2) large current discharge

Cruise, 20 kilometers electric current is commonly 4 a, the value is higher than other areas of the battery working current, overload and speeding the working current of electric cars is even greater. Charging battery manufacturers have been 1 c 70%, 60% of the 2 c discharge cycle life test. Life test in this way, can achieve the life of the battery charge and discharge cycle of 350 times a lot, but in actual use effect is far. This is because the large current work a 50% increase in the depth of discharge, the battery will accelerate vulcanization. So, three-wheeled motorcycle battery life shorter, because three rounds of motorcycle body is too heavy, working current of more than 6 a.

(3) high charge and discharge frequency

In the backup battery in the field of power supply, only in the power failure will discharge, if stop eight times a year, to 10 years of life, only do 80 - cycle recharge life, and electric vehicle charging and discharging cycle of 300 times a year or more are common.

(4) short time charging

Due to the electric bicycle is traffic tools, there is little time, rechargeable in 8 hours to complete. 36 v or 48 v 20 ampere hour charging, it will have to improve charging voltage (generally for single section 2.7 ~ 2.9 v), when the charging voltage exceeds oxygen evolution of the single battery voltage (2.35 v) or hydrogen evolution voltage (2.42 v), the battery will open valve exhaust due to excessive oxygen, cause water loss, increase the concentration of electrolyte, vulcanization phenomenon aggravate of the battery.

(5) is not charging in time after discharge

As traffic tools, electric bicycle charging and discharging is completely separated, it difficult to conditional charging in time after discharge, the discharge after the formation of a large number of lead sulfate if more than half an hour without a charge reduction of lead oxide, sulfide formed crystals.

3, lead battery production reasons

For electric bicycle with the particularity of lead-acid battery, the battery manufacturers have taken different approaches. The most typical method is as follows:

(1) to increase the number of plates.

The original design of the single system of 5 6 pills instead of 6 7 pills, 7 8 pills is made, and even system of 8 9 pills. By thinning the thickness of the plate and baffle plate, and increase the quantity of plate to increase the battery capacity.

(2) improve the proportion of sulfuric acid battery.

Original floating battery proportion of sulfuric acid is generally between 1.21 ~ 1.28, and electric bicycle battery acid proportion generally at around 1.36 ~ 1.38, so that we can provide larger current, improve the early stages of the battery capacity.

(3) increase the positive plate of lead oxide active material dosage and proportion.

Increase lead oxide increases the participation in discharge of electrochemical reaction substances, also increased the discharge time, increase the battery capacity.

Through these measures, the early stages of the battery capacity can satisfy the demands of the electric bicycle capacity, especially for the large current discharge characteristic of the battery. Plate, however, increased, the capacity of the sulfuric acid is reduced, the battery heating, resulting in a large number of water loss, at the same time, the battery short circuit and lead graft bypass probability increased. Raise the proportion of sulfuric acid increased the initial capacity of the battery, but the sulfide phenomenon is more serious. Sealed battery is one of the most basic principle of positive plate after oxygen, oxygen directly to the negative plate, absorbed by the negative plate and the reduction of water, the technology assessment battery indicator parameters are called "sealed reaction efficiency", this phenomenon is called "oxygen cycle". Little water loss in this way, the battery and the "maintenance", is free of water. Therefore, are required to do negative plate capacity than the positive plate capacity, also known as the cathode. Increase the positive plate must make active material and the negative transfer reduced, less oxygen cycle, water loss increases, and sulfide. Although these measures promoted the early stages of the battery capacity, but it will cause water loss and sulfide, and water loss and sulfide and can contribute to each other, the end result is to sacrifice the life of the battery.

There is a group of virtual assembly welding problem. Is easy to generate virtual welding place plate. And each cell of the single have 15 pieces of plate, is 15 solder joints, a six single cell battery, there are 90 solder joints, a group of cells by 3The 12 v battery. There are 270 solder joints. If a solder joint is empty welding, the single cell capacity will drop, and the single cell battery behind formation, causing the whole battery, battery can form a serious imbalance, disable this set of batteries in advance. Even if virtual welding control in one over ten thousand, the average 37 battery will have a set of battery is empty welding, this is absolutely can not allowed. And lead calcium alloy plate grid cell, when welding can precipitate calcium and cover welding problem, in this way, many battery manufacturers prefer to use low antimony alloy plate gate without use of lead calcium alloy. And low antimony alloy plate gate voltage of oxygen evolution activity of hydrogen evolution is lower, the battery has a large air output, water loss is relatively serious, battery sulfide more easily.

4, the electric bicycle production reasons

Most car controller left a line loss plug, many dealers to attract customers to remove the speed limit. Some factory simply remove the speed limiter can attract customer value speed, also can reduce costs, such a car in high speed when the current is very big, will shorten the battery life seriously.

The lowest protection voltage of 12 V lead-acid battery is 10.5 V, if it is36 v battery group, the minimum retention voltage is 31.5 V, the controller in use most automakers under-voltage protection voltage is 31.5 V. On the surface it's the right, but actually when only 31.5 V to 36 V battery voltage, because the battery capacity is poor, certainly there will be a battery voltage is lower than 10.5 V, the battery is in the midst of a discharge. At that time, discharge of battery capacity fell sharply, then the damage influence to the battery is not only the single battery only, but affect the whole life of the battery. In fact, after the battery voltage is lower than 32 v until 27 v, the additional line continuation ability is less than 2 km, and the damage in the battery is very large. As long as you appear such circumstance, 10 times the capacity of the battery will be less than 70% of the nominal capacity. In addition, some users find the battery after the under-voltage, over 10 minutes, the battery without under voltage, then take to go to the greater damage to the battery, and most of the car's manual is not give warning to the user. At present within the majority of the controller are adjustable potentiometer, and the adjustable potentiometer the vibration of the drift is more serious. In price competition, facing users pay more attention to car appearance, there are few products using vibration precision potentiometer, this kind of controller again drift after vibration.

5, the reason of charging equipment

The industry widely circulated a words be: not the battery is bad, is bad. In order to meet the short-term high capacity of electric bicycle battery charging, in a three-stage constant-voltage charging current limiting, had to improve the constant pressure value to 2.47 V to 2.49 V. In this way, considerably more than the battery positive plate oxygen voltage and the voltage of negative plate activity of hydrogen evolution. Some charger manufacturers of products in order to reduce the charging time, improves the floating charge current constant voltage, and makes the charging indicator after a full charge, has not yet been charged, depends on float charging pressure increases to compensate for. So many chargers float charging pressure more than the single voltage 2.35 V, so also in a large number of oxygen evolution in floating phase. And battery oxygen cycle is bad, so in the floating phase are exhaust. Constant pressure value is high, to ensure the charging time, but the sacrifice is water loss and sulfide. Constant pressure value low, charging time and filling the electricity and is difficult to guarantee. In the improvement of panels of battery grid alloy, improve the formation of gas, the improvement of oxygen cycle performance, improve the efficiency of sealed reaction, on the basis of charging control top charging voltage below 2.42 V, which is under hydrogen evolution potential. Doing that will inevitably lead to the extension of charging time, it must be in the big electric current charge (current-limiting charging), join the negative pulse of depolarization, improve battery charging accept ability, when large current charging into some more power, shorten the charging time.70% of the charging current, 2 c is battery capacity is larger, in charge of battery with large current charging, the battery is less damage. The voltage of battery has virtually no higher than serious activity of hydrogen evolution. Once the voltage is higher than the hydrogen evolution, and the battery will be rapid water loss. Using this kind of charger, must adopt continuous charging and discharging, if midway stop charging a few days, the battery can produce a serious of sulfide and failure in advance. And users to use, the battery is there is no guarantee that every time after use, can charge in time, within a year occurred several times without charge in time, the battery of vulcanization will accumulate. Most charger manufacturers said depot because prices don't accept can guarantee the life of the battery charger. Admittedly, this is most small businesses are so, however, with the development of the high price, large scale enterprise really can't buy a good charger. Some charger manufacturers exaggerate certain function, as well as the effect of finished product without its propaganda. There are many function belongs to sell the concept of function, effect is limited.

6, other reasons

Many batteries in the unit tests, can obtain better results, however, for string battery, due to capacity, open-circuit voltage, charged state and degree of cure each are not identical, this difference can be expanded in series battery pack, will affect the whole state of monomer battery, its life is significantly lower.

From battery charge on the production line, to the user with car after car use this period of time to go through a lot of link, the time interval for months, even during this time, because not to supply electricity, battery self-discharge accumulated amount of lead sulfate crystallization, the user just buy a new battery aging may have even a subscription fee.

Battery manufacturers in performing quality assurance recycles the battery is not completely eliminated. Battery back to back, charging and discharging test battery manufacturers, often in the inspection found that more than 60% of monomer battery is not eligible for return back the battery. Its reason is in series battery pack, the individual battery behind the form a complete set of functions decline caused by the entire group to return back. Many battery manufacturers to return back the battery to match group, after filling water, in addition to sulfur, packaging, and to provide to the user, in order to improve the effective of battery service life, reduce scrap rate, reduce the part of the claim loss of battery manufacturers, so, many dealers have feel the battery manufacturers provide obvious "generation than a generation".

Third, how to solve the battery sulfide

To reduce the battery sulfide, prolong the service life of the battery, first of all to improve working conditions for electric bikes. Reduce the body weight, get rid of unnecessary decoration, appropriate speed limits, do not carry heavy things, the electric bicycle is not used for a long time to do addition charge, best can timely charge after each discharge, completes the under-voltage protection, defend the battery discharge, the nominal 24 V under-voltage protection should be located in 22 V, 21.5 V ~ for nominal 36 V under-voltage protection should choose + / - 0.5 V, 32.5 V for nominal 48 V should be located in 44 V ~ 45 V. This voltage is less than 2 km to the line continuation ability only reduce, but can effectively extend the service life of the battery. Regularly every three months to professional maintenance station maintenance battery, filling water in a timely manner. The method is simple, economic cost is low, but it has the certain difficulty to strictly abide by. So, you can use the special equipment for sulphur removal maintenance, these methods are:

1. Use desktop rapid sulphur removal device

Desktop rapid sulphur removal equipment principle of work is high voltage large current pulse charging and eliminated by negative sniper wear sulfide. This method is fast, work fast, can get temporarily eliminate the effect of vulcanization, but the high voltage large current can strike in addition to sulfur can also in addition to the active substances, in removing sulfide have serious water loss and positive plate to soften, produce fatal damage to the battery, after two such devices in addition to sulfur battery basic will be scrapped. In addition, the current professional maintenance point on a sulphur removal is basic in the 60-80 yuan between, can extend battery life half a year at most, and not for the user to remarkable economic benefits. At present, the professional battery maintenance shop owners are on the market already understand the dangers of this approach. As a result, there is a pulse discharge sulphur removal device, in fact, the fundamental principle and does not change, just from the constant pressure Evergrande into high voltage instantaneous peak current, or will damage the plate active substances, used a friend should be clear that this type of product.

2. The choice is in addition to sulfur charger

At present there are three kinds of sulfur in addition to the charger works, one kind is analogous to the working principle of the desktop rapid sulphur removal device adopts high voltage large current pulse charging, through the negative scope, in addition to sulfur, have above illustrates this method for battery life would amount to a fatal injury, has been rejected by the market. The second is to use fast pulse edge charge and discharge pulse, using instantaneous peak, sulfide interference in the process of charging the battery. Another kind is a cyclical use of 10% ~ 20% of charging method, reduction of lead sulfate crystallization of the battery. When both the charger can charge the battery in addition of sulfur, can cause owe or overcharge, also ignore the battery discharge process is the fact that the main sulfide process, so the effect is not ideal, most users after with electric vehicles equipped with the charger will give up this duplication of investment way of sulphur removal.

3. The use of lead-acid battery on-line nobu

On-line lead-acid battery generate device and batteries in parallel, can prevent and eliminate vulcanization twenty-four hours. This method repair slowly, repair time is long, often in 120 hours, but whether it is a charge and discharge process can prevent and eliminate sulfide, repair effect is very good. Because of low voltage with low current, generate device will not lead to a powerful impact on battery plate water loss and softening, and it is a kind of user input can perserve way of maintenance, especially for the new battery quality is good, can prolong the battery life of 2 ~ 5 times, and an input, can be associated with electric auto, the next to replace batteries, generate device also can continue to use, can save a lot of economic costs. If the user has a year to replace a battery, a set of batteries, 280 yuan, users will be 10 years spent 2800 yuan on the replacement of batteries, conservative calculation, if use generate device to extend battery life twice, 10 years also can cut down the cost of nearly half of the battery.

Adopt this method is of great significance. Is first brought tangible economic benefits to the user, reducing the user's trouble. The second is to improve the reputation of the depot, provides conditions for expanding production. Third, in order to solve the electric car dealers battery warranty, very hard, reduce complaints, improve the credibility, increasing profit and at the same time, also increased the transaction on store sales sales plan. Fourth, can greatly reduce the battery manufacturer's claims. Fifth, improve the image of electric bicycles, electric bicycle overall market development. Sixth, improve the utilization rate of the battery, which is beneficial to environmental protection.

The page contains the contents of the machine translation.