（一）铅酸蓄电池的结构

铅酸蓄电池主要由正极板组､负极板组､隔板､容器和电解液等构成,其结构如下图所示：




1.极板

铅酸蓄电池的正､负极极板由纯铅制成,上面直接形成有效物质,有些极板用铅镍合金制成栅架,上面涂以有效物质｡正极(阳极)的有效物质为褐色的二氧化铅,这层二氧化铅由结合氧化的铅细粒构成,在这些细粒之间能够自由地通过电解液,将正极材料磨成细粒的原因是可以增大其与电解液的接触面积,这样可以增加反应面积,从而减小蓄电池的内阻｡负极(阴极)的有效物质为深灰色的海绵状铅｡在同一个电池内,同极性的极板片数超过两片者,用金属条连接起来,称为极板组或极板群｡至于极板组内的极板数的多少,随其容量(蓄电能力)的大小而异｡为了获得较大的蓄电池容量,常将多片正､负极板分别并联,组成正､负极板组,如下图所示：




安装时,将正､负极板组相互嵌合,中间插入隔板,就形成了单格电池｡在每个单格电池中,负极板的片数总要比正极板的片数多一片,从而使每片正极板都处于两片负极板之间,使正极板两侧放电均匀,避免因放电不均匀造成极板拱曲｡

2.隔板

在各种类型的铅酸蓄电池中,除少数特殊组合的极板间留有宽大的空隙外,在两极板间均需插入隔板,以防止正､负极板相互接触而发生短路｡这种隔板上密布着细小的孔,既可以保证电解液的通过,又可以阻隔正､负极板之间的接触,控制反应速度,保护电池｡隔板有木质､橡胶､微孔橡胶､微孔塑料､玻璃等数种,可根据蓄电池的类型适当选定｡吸附式密封蓄电池的隔板是由超细玻璃丝绵制作的,这种隔板可以把电解液吸附在隔板内,吸附式密封蓄电池的名称也是由此而来的｡

3.容器

容器是用来盛装电解液和支撑极板的,通常有玻璃容器､衬铅木质容器､硬橡胶容器和塑料容器四种｡容器用于盛放电解液和极板组,应该耐酸､耐热､耐震｡容器多采用硬橡胶或聚丙烯塑料制成,为整体式结构,底部有凸起的肋条以搁置极板组｡壳内由间壁分成3个或6个互不相通的单格,各单格之间用铅质联条串联起来｡容器上部使用相同材料的电池盖密封,电池盖上设有对应于每个单格电池的加液孔,用于添加电解液和蒸馏水以及测量电解液密度､温度和液面高度｡

4.电解液

铅酸蓄电池的电解液是用蒸馏水稀释高纯浓硫酸而成的｡它的密度高低视铅蓄电池类型和所用极板而定,一般在15℃时为1.200～1.300g/cm3｡蓄电池用的电解液(稀硫酸)必须保持纯净,不能含有危害铅酸蓄电池的任何杂质｡电解液的作用是给正､负电极之间流动的离子创造一个液体环境,或者说充当离子流动的介质｡电解液的相对密度对蓄电池的工作有重要影响,相对密度大,可减少结冰的危险并提高蓄电池容量,但相对密度过大,则黏度增加,反而降低蓄电池容量,缩短使用寿命｡应根据当地最低气温或制造厂家的要求选择电解液相对密度｡

5.加液孔盖

加液孔盖用橡胶或塑料制成,旋在电池盖的加液孔内，如下图：




加液孔盖上有通气孔,可使蓄电池化学反应中产生的气体顺利排出｡加液孔盖上的通气孔应经常保持畅通,使蓄电池内部的氢气与氧气排出,防止蓄电池过早损坏或爆炸｡

6.联条

由于蓄电池各单格为串联连接,因此不同极性的极柱要用联条连接起来｡联条用铅锑合金铸成,有外露式､跨桥式和穿壁式三种,前者用在硬橡胶外壳和盖上,后两者用在塑料外壳和盖上｡外露式是指联条外露在蓄电池的上面;跨桥式是指联条下部在蓄电池的平面上或埋在盖下,连接部分跨接在各单格电池的中间壁上;穿壁式是指在中间壁上打孔,使极板组柄直接穿过中间隔壁将各单格电池连接起来｡穿壁式联条的连接方式如下图所示：




（二）铅酸蓄电池的基本概念

1.充电

充电是外电路给蓄电池供电,使电池内发生化学反应,从而把电能转化为化学能储存起来的操作｡充电时,蓄电池的正､负极分别与直流电源的正､负极相连,当充电电源的端电压高于蓄电池的电动势时,在电场的作用下,电流从蓄电池的正极流入､负极流出,这一过程称为充电｡蓄电池充电过程是将电能转换为化学能的过程｡充电时,正､负极板上的PbSO4还原为PbO2和Pb,电解液中的H2SO4不断增多,电解液密度不断上升｡当充电接近终了时,PbSO4已基本还原成 Pb｡过剩的充电电流将电解水,使正极板附近产生O2从电解液中逸出,负极板附近产生H2从电解液中逸出,电解液液面高度降低｡因此,铅酸蓄电池需要定期加蒸馏水｡

蓄电池充足电的标志是:

(1)电解液中有大量气泡冒出,呈沸腾状态;

(2)电解液的相对密度和蓄电池的端电压上升到规定值,且在2～3h内保持不变｡

2.放电

放电是在规定的条件下,电池向外电路输出电能的过程｡当铅酸蓄电池接上负载后,在电动势的作用下,电流就会从蓄电池的正极经外电路的用电设备流向蓄电池的负极,这一过程称为放电,蓄电池的放电过程是将化学能转化为电能的过程｡放电时,正极板上的 PbO2和负极板上的Pb都与电解液中的 H2SO4反应生成硫酸铅(PbSO4),沉附在正､负极板上｡在这个过程中,电解液中的H2SO4不断减少,电解液密度不断下降｡理论上,放电过程可以进行到极板上的活性物质被耗尽为止,但由于生成的 PbSO4沉附于极板表面,阻碍电解液向活性物质内层渗透,使得内层活性物质因缺少电解液而不能参加反应,因此在使用中放完电时蓄电池活性物质的利用率也只有20% ～30%｡因此,采用薄型极板,增加极板的多孔性,可以提高活性物质的利用率,增大蓄电池的容量｡

蓄电池放电终了的特征是:

(1)单格电池电压降到放电终止电压;

(2)电解液相对密度降到最小许可值｡

放电终止电压与放电电流的大小有关,放电电流越大,允许的放电时间就越短,放电终止电压也越低｡

3.过充电

过充电是对完全充电的蓄电池或蓄电池组继续充电｡

4.自放电

自放电是电池的能量没有通过放电就进入外电路,造成一定能量的损失｡

5.活性物质

在电池放电时发生化学反应从而产生电能的物质,或者说是正极和负极储存电能的物质的统称｡

6.放电深度

放电深度是指蓄电池使用过程中放电到什么程度才停止放电｡

7.板极硫化

在使用铅酸蓄电池时要特别注意的是:电池放电后要及时充电,如果长时间处于半放电或充电不足甚至过充的情况,或长时间充电和放电都会形成 PbSO4晶体｡这种大块晶体很难溶解,无法恢复原来的状态,导致板极硫化后充电就会变得困难｡

8.容量

容量是在规定的放电条件下电流输出的电荷,其单位常用安时(A·h)表示｡

9.相对密度

相对密度是指电解液与水的密度比值,用来检验电解液的强度｡相对密度与温度变化有关｡25℃时充满的电池电解液相对密度值为1.265｡密封式电池,相对密度值无法测量｡纯酸溶液的密度为1.835g/cm3,完全放电后降至1.120g/cm3｡电解液注入水后,只有待水完全融合电解液后才能准确测量密度,融入过程大约需要数小时或者数天,但是可以通过充电来缩短时间｡每个电池的电解液密度均不相同,即使是同一个电池在不同的季节,电解液的密度也会不一样｡大部分铅酸蓄电池的电解液密度在1.1～1.3g/cm3范围内,充满电之后一般为1.23～1.3g/cm3｡

10.运行温度

电池在使用一段时间后,会感觉烫手,这是因为铅酸蓄电池具有很强的发热性｡当运行温度超过25℃,每升高10℃,铅酸电池的使用寿命就减少50%,所以电池的最高运行温度应比外界低,在温度变化超过±5℃的情况下最好｡

（三）铅酸蓄电池充､放电基本原理

在铅酸蓄电池中,正极板为PbO2,负极板为 Pb,电解液为 H2SO4｡将其正､负极板插入电解液中,正､负极板与电解液相互作用,在正､负极板间就会产生约2.1V的电势｡电池在完成充电后,正极板为二氧化铅,负极板为海绵状铅｡放电后,在两极板上都产生细小而松软的硫酸铅,充电后又恢复为原来物质｡铅酸蓄电池在充电和放电过程中的可逆反应理论比较复杂,目前公认的是哥来德斯东和特利浦两人提出的“双硫酸化理论”｡该理论的含义:铅酸蓄电池在放电后,正､负电极的有效物质和硫酸发生反应,均转变为硫酸化合物(硫酸铅),充电时又会转化为原来的铅和二氧化铅｡其具体的化学反应方程式如下:

正极

2PbO2+2H2SO4 →2PbSO4+O2↑+2H2O

负极

Pb+H2SO4 →PbSO4+H2↑

总反应

2PbO2+3H2SO4+Pb →3PbSO4+2H2O+O2↑+H2↑

从以上的化学反应方程式中可以看出,铅酸蓄电池在放电时,正极的活性物质二氧化铅和负极的活性物质铅都与硫酸电解液反应,生成硫酸铅,在电化学上把这种反应叫做“双硫酸盐化反应”｡在蓄电池刚放电结束时,正､负极活性物质转化成的硫酸铅是一种结构疏松､晶体细密的物质,活性程度非常高｡在蓄电池充电过程中,正､负极疏松细密的硫酸铅,在外界充电电流的作用下会重新变成二氧化铅和铅,蓄电池又处于充足电的状态｡

由此可知以上反应是可逆的｡正是这种可逆的电化学反应,使蓄电池实现了储存电能和释放电能的功能｡人们在日常使用中,通常使用蓄电池的放电功能,把充电作为蓄电池的维护｡铅酸蓄电池在充足电的情况下可以长时间保持电池内化学物质的活性,而在蓄电池放电以后,如果不及时充足电,电池内的活性物质很快就会失去活性,使电池内部产生不可逆的化学反应｡所以对太阳能蓄电池和其他用途的铅酸蓄电池,应充足电保存,并定期给电池补充电｡
（1） Structure of lead-acid battery



The lead-acid battery is mainly composed of positive plate group, negative plate group, separator, container and electrolyte, and its structure is shown in the following figure:






1. Plate



The positive and negative electrode plates of lead-acid batteries are made of pure lead, and the effective substances are directly formed on them. Some electrode plates are made of lead-nickel alloy and coated with effective substances. The effective substances of the positive electrode (anode) are brown lead dioxide. This layer of lead dioxide is composed of combined oxidized lead particles. The reason why these particles can freely pass through the electrolyte and grind the positive material into fine particles is to increase its contact area with the electrolyte, This can increase the reaction area and reduce the internal resistance of the battery. The effective material of the negative electrode (cathode) is dark gray spongy lead. In the same battery, if the number of plates of the same polarity exceeds two, they are connected by metal strips, which is called the plate group or plate group. The number of plates in the plate group varies with its capacity (storage capacity). In order to obtain a larger battery capacity, Multiple positive and negative plates are usually connected in parallel to form positive and negative plate groups, as shown in the following figure:






During installation, insert the positive and negative plates into each other, and insert a partition in the middle to form a single-cell battery. In each single-cell battery, the number of negative plates is always more than the number of positive plates, so that each positive plate is between the two negative plates, so that the discharge on both sides of the positive plate is uniform, and avoid the plate arch caused by uneven discharge



2. Diaphragm



In all types of lead-acid batteries, except for a few special combination of plates with wide gap between them, a partition shall be inserted between the two plates to prevent short circuit due to contact between the positive and negative plates. This partition is densely covered with small holes, which can not only ensure the passage of electrolyte, but also block the contact between the positive and negative plates, and control the reaction speed, Protect the battery. There are several types of separators, such as wood, rubber, microporous rubber, microporous plastic, glass, etc., which can be appropriately selected according to the type of battery. The separators of the adsorption sealed battery are made of superfine glass wool, which can adsorb the electrolyte in the separators. The name of the adsorption sealed battery is also derived from this



3. Container



Containers are used to hold electrolyte and supporting plates, usually including glass containers, lead-lined wooden containers, hard rubber containers and plastic containers. Containers are used to hold electrolyte and plate groups, and should be acid, heat and shock resistant. Containers are mostly made of hard rubber or polypropylene plastic, which is an integral structure, with raised ribs at the bottom to hold the plate group. The shell is divided into 3 or 6 separate cells by the partition wall, Each cell is connected in series with a lead mass link. The upper part of the container is sealed with a battery cover of the same material. The battery cover is equipped with a liquid filling hole corresponding to each cell, which is used to add electrolyte and distilled water and measure the density, temperature and liquid level of the electrolyte



4. Electrolyte



The electrolyte of lead-acid battery is made by diluting high-purity concentrated sulfuric acid with distilled water. Its density depends on the type of lead-acid battery and the electrode plate used, which is generally 1.200~1.300g/cm3 at 15 ℃. The electrolyte (dilute sulfuric acid) used for the battery must be kept pure, and cannot contain any impurities harmful to the lead-acid battery. The function of the electrolyte is to create a liquid environment for the ions flowing between the positive and negative electrodes, Or act as the medium of ion flow. The relative density of electrolyte has an important impact on the work of the battery. The high relative density can reduce the risk of icing and improve the battery capacity. However, if the relative density is too high, the viscosity will increase, but the battery capacity will be reduced and the service life will be shortened. The relative density of electrolyte should be selected according to the local minimum temperature or the requirements of the manufacturer



5. Filling hole cover



The filling hole cover is made of rubber or plastic and screwed into the filling hole of the battery cover, as shown in the following figure:






There is a vent hole on the filling hole cover to allow the gas generated in the chemical reaction of the battery to be discharged smoothly. The vent hole on the filling hole cover should always be kept unblocked to allow the hydrogen and oxygen inside the battery to be discharged, and prevent the battery from premature damage or explosion



6. Coupon



Because each cell of the battery is connected in series, the poles of different polarity should be connected with a connecting rod. The connecting rod is made of lead-antimony alloy, and there are three types of exposed type, bridge type and wall-through type. The former is used on the hard rubber shell and cover, and the latter two are used on the plastic shell and cover. The exposed type refers to the connecting rod exposed on the battery; Cross-bridge type means that the lower part of the connecting strip is on the plane of the battery or buried under the cover, and the connecting part is bridged on the middle wall of each single cell battery; The wall-through type refers to punching holes in the middle wall, so that the handle of the plate group directly passes through the middle wall to connect the single cell batteries. The wall-through type connection mode is shown in the following figure:






（2） Basic concepts of lead-acid batteries



1. Charging



Charging is an operation in which the external circuit supplies power to the battery to make the chemical reaction occur in the battery, thus converting the electric energy into chemical energy for storage. During charging, the positive and negative poles of the battery are respectively connected with the positive and negative poles of the DC power supply. When the terminal voltage of the charging power supply is higher than the electromotive force of the battery, under the action of the electric field, the current flows in and out of the positive pole of the battery, This process is called charging. The battery charging process is the process of converting electrical energy into chemical energy. During charging, the PbSO4 on the positive and negative plates is reduced to PbO2 and Pb, the H2SO4 in the electrolyte is increasing, and the density of the electrolyte is rising. When the charging is close to the end, PbSO4 has been basically reduced to Pb. The excess charging current will electrolyze water, making the O2 generated near the positive plate escape from the electrolyte, and the H2 generated near the negative plate escape from the electrolyte, The height of the electrolyte level is reduced. Therefore, the lead-acid battery needs to be regularly added with distilled water



The sign of sufficient battery power is:



(1) There are a lot of bubbles in the electrolyte, which are boiling;



(2) The relative density of the electrolyte and the terminal voltage of the battery rise to the specified value and remain unchanged within 2~3h



2. Discharge



Discharge is the process of the battery outputting electric energy to the external circuit under specified conditions. When the lead-acid battery is connected to the load, under the action of electromotive force, the current will flow from the positive pole of the battery to the negative pole of the battery through the electrical equipment of the external circuit. This process is called discharge. The discharge process of the storage battery is the process of converting chemical energy into electric energy, Both PbO2 on the positive plate and Pb on the negative plate react with H2SO4 in the electrolyte to form lead sulfate (PbSO4), which is deposited on the positive and negative plates. During this process, H2SO4 in the electrolyte keeps decreasing, and the density of the electrolyte keeps decreasing. In theory, the discharge process can be carried out until the active substance on the plate is exhausted, but the generated PbSO4 is deposited on the surface of the plate, preventing the electrolyte from penetrating into the inner layer of the active substance, The inner active substance cannot participate in the reaction due to the lack of electrolyte, so the utilization rate of the active substance of the battery is only 20%~30% when the battery is discharged during use. Therefore, the use of thin plates to increase the porosity of the plates can improve the utilization rate of the active substance and increase the capacity of the battery



The characteristics of the end of battery discharge are:



(1) The single cell battery voltage drops to the discharge termination voltage;



(2) The relative density of electrolyte is reduced to the minimum allowable value



The discharge termination voltage is related to the discharge current. The larger the discharge current, the shorter the allowable discharge time and the lower the discharge termination voltage



3. Overcharge



Overcharging is to continue charging the fully charged battery or battery pack



4. Self-discharge



Self-discharge means that the energy of the battery enters the external circuit without discharging, resulting in certain energy loss



5. Active substances



The substances that produce electric energy by chemical reaction during battery discharge, or the substances that store electric energy at the positive and negative poles



6. Discharge depth



The discharge depth refers to the extent to which the battery stops discharging during use



7. Plate vulcanization



When using lead-acid batteries, special attention should be paid to the following: the batteries should be charged in time after discharge. If they are in the condition of semi-discharge or under-charge or overcharge for a long time, or if they are charged and discharged for a long time, PbSO4 crystals will be formed. This large crystal is difficult to dissolve and cannot restore its original state, resulting in the difficulty of charging after the plate is vulcanized



8. Capacity



Capacity is the current output charge under the specified discharge conditions, and its unit is usually ampere-hour (A · h)



9. Relative density



Relative density refers to the density ratio of electrolyte and water, which is used to test the strength of electrolyte. The relative density is related to the temperature change. The relative density value of the battery electrolyte filled at 25 ℃ is 1.265. The relative density value of sealed battery cannot be measured. The density of pure acid solution is 1.835g/cm3, which is reduced to 1.120g/cm3 after full discharge. After the electrolyte is injected into water, the density can be accurately measured only after the water completely fuses the electrolyte, The melting process takes about hours or days, but the time can be shortened by charging. The electrolyte density of each battery is different, even if the same battery is in different seasons, the density of the electrolyte will be different. The electrolyte density of most lead-acid batteries is in the range of 1.1~1.3g/cm3, and generally is 1.23~1.3g/cm3 after full charge



10. Operating temperature



After using the battery for a period of time, it will feel hot because the lead-acid battery has a strong heat. When the operating temperature exceeds 25 ℃, the service life of the lead-acid battery will be reduced by 50% for every 10 ℃ increase, so the maximum operating temperature of the battery should be lower than the outside world, and it is best when the temperature change exceeds ± 5 ℃



（3） Basic principle of lead-acid battery charging and discharging



In lead-acid batteries, the positive plate is PbO2, the negative plate is Pb, and the electrolyte is H2SO4. Insert its positive and negative plates into the electrolyte, and the interaction between the positive and negative plates and the electrolyte will generate a potential of about 2.1V between the positive and negative plates. After the battery is charged, the positive plate is lead dioxide, and the negative plate is spongy lead. After discharge, small and soft lead sulfate will be produced on both plates, After charging, it will return to the original material. The reversible reaction theory of lead-acid battery during charging and discharging is relatively complex. It is currently recognized that the "double sulfation theory" proposed by Goldstone and Philips. The meaning of this theory: after discharging, the effective material of the positive and negative electrodes of lead-acid battery will react with sulfuric acid, and both will be converted into sulfuric acid compound (lead sulfate), When charging, it will be converted into the original lead and lead dioxide. The specific chemical reaction equation is as follows:



positive electrode



2PbO2+2H2SO4 →2PbSO4+O2↑+2H2O



negative pole



Pb+H2SO4 →PbSO4+H2↑



Total reaction



2PbO2+3H2SO4+Pb →3PbSO4+2H2O+O2↑+H2↑



From the above chemical reaction equation, it can be seen that when the lead-acid battery is discharged, the active material lead dioxide of the positive pole and the active material lead of the negative pole react with the sulfuric acid electrolyte to produce lead sulfate, which is called "bisulfate reaction" in electrochemistry. At the end of the discharge of the battery, the active material of the positive and negative pole converts into lead sulfate, which is a substance with loose structure and fine crystal, The degree of activity is very high. During the charging process of the battery, the loose and fine lead sulfate at the positive and negative sides will become lead dioxide and lead again under the action of the external charging current, and the battery will be fully charged



It can be seen that the above reactions are reversible. It is this reversible electrochemical reaction that makes the battery realize the function of storing and releasing electric energy. In daily use, people usually use the discharge function of the battery and take charging as the maintenance of the battery. Lead-acid battery can maintain the activity of chemical substances in the battery for a long time when it is fully charged, and if it is not fully charged in time after the battery is discharged, The active substance in the battery will soon lose its activity, causing irreversible chemical reaction inside the battery. Therefore, solar batteries and lead-acid batteries for other purposes should be stored with sufficient electricity, and the battery should be recharged regularly

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本文由韩国SEBANG蓄电池（大陆地区）营销中心于2023-03-04 13:02:14 整理发布。
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