Construction of lead acid battery

Overview of lead acid battery

It is the main overview of lead acid battery,working and construction.

In lead acid battery there is a group of cells and in each cell there is one group of positive plates and one group of positive plates and one group of negative plates. The positive plates are made of lead peroxide (PbO2) and negative plate is made of spongy lead. Thus for identification the positive plate as the color of dark brown, whereas the negative plate as the color of light salty,

Construction of lead acid battery

In this topic we are discussing about the lead acid battery working , and construction . mainly construction

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Main parts of lead acid battery

1. Separator.

It is most important part of lead acid battery. Which separate the positive and negative plates from each other and prevents the short circuit? The separators must be porous so that the electrolyte may circulate between the plates . The separators must have higher insulating resistance and mechanical strength. The material used for separators are wood, rubber, glass wood mate, pvc.

2. Electrolyte 

in lead acid battery dilute sulphuric acid (H2SO4)is used as an electrolyte. For this purpose one part concentrated sulphuric acid is mixed with three parts of distilled water.

3. Container.

Container is a box of vulcanized rubber, molded rubber, molded plastic, glass or ceramic , on the base of this box there are supports block on which the positive and negative plates are established. Thus between this supports there are grooves which works like a mud box. The active material separated from the plates get collected in this mud box and it cannot make the contact with the plates thus the internal faults due to the mud are avoided.

4. Cover of cell. 

In lead acid battery it is also made of the same material which is used is used for making container. It is used to cover the complete cell after the installation of the plates in it . it protects the cell from the dust as well as other external impurities.

5. Vent plug.

The vent plug are provide in the cover plate of the cell which are used to fill up the electrolyte in the cell or the inspection of internal condition of the cell the vent plugs  are aslo use for to exhaust the gases generated in the cell to the atmosphere.

6. Connecting bar.

It works like a link and used to connect the two cells in series. Terminal of one cell and negative terminal of another cell.

7 terminal posts

There are the terminals of the battery which are connected to charging circuit as well as the load. For identification the diameter of the positive terminal is design more as compared to the negative terminal.
Hence it is the lead acid battery construction, working also discuss below.

 lead acid battery, working

Dilute sulfuric acid used for lead acid battery   has ration of acid: water = 1:3.
This lead acid storage battery   is formed by dipping lead peroxide plate and sponge lead plate in dilute sulfuric acid. A load is connected externally between these plates. In diluted sulfuric acid the molecules of the acid split into positive hydrogen ions  and negative sulfate ions  . The hydrogen ions when reach at PbO2 plate, they receive electrons from it and become hydrogen atom which again attack PbO2 and form PbO and H2O (water). This PbO reacts with H2 SO4 and forms PbSO4 and H2O (water).

Hence it is the lead acid battery, construction and working.

                      periodic maintenance of lead acid battery .

1. Do not allow the battery to stand idle for long time this may cause inactivation of the battery cells.


2. Do not charge the battery with very high rate of current because high rate of charging causes high temperature rise and excessive gassing resulting in heavy loss of water and sometime overflowing of electrolyte from the battery cells.
3. After every complete discharge, the battery should be immediately charged before returning it to its regular floating service. Otherwise there may be a chance of deposition of sulphate film on the plates.
4. As already mentioned, the battery cells should be charged gently at normal rate so that there will be no chance of immediate gassing and temperature rise over 40°C. Otherwise there may be damage to the battery cells due to high temperature. During charging of batteries, continuous monitoring is required, if gassing starts and the temperature reaches the said limit, reduce the rate of charging. If after reducing the charging rate, the temperature is still approaching to the limit, it indicates the completion of charging process because even the normal rate of charging may produce high temperature rise if the battery approaches to the fully charged condition.
5. The voltage of each of the battery cells should be checked before conclusion of charging and each of the cells are properly and equally charged and the readings should also be tallied with previous record.
6. If the electrolyte level inside the battery cell comes down, it must be filled with distilled water up to the level marked on the cell itself. This is to compensate the loss of water due to evaporation.
7. During filling up distilled water in the battery cell, it must be carefully watched that the electrolyte level in the battery cells should not exceed the line marked on it. Otherwise there may be a chance of overflowing of electrolyte during gassing of the battery. High level of electrolyte may also cause softening the sealing compound on the top cover and subsequent leakage in the battery cell.
8. The specific gravity should be measured after at least two weeks from topping up to ensure thorough mixing of water in electrolyte.
9. The battery should be discharged up to the allowable limit and then it should be overcharged once in 2 to 3 months. The rate of overcharging must be followed as specified by the manufacturer. This operation is very important to maintain the acid storage battery in the active state.
10. When specific gravity of electrolyte is measured, it should not be forgotten to correct it for temperature. So that, all hydrometer readings will be referred to same temperature. The hydrometer should be kept clean with distilled water otherwise the hydrometer will cause incorrect readings and as well as spoil the quality of electrolyte. The specific gravity of electrolyte must be kept within 1.180 to 1.240. Low value of specific gravity decreases the capacity of battery and on the other hand high value is harmful for the battery plates.
11. The substation battery normally operates under floating mode. At floating mode, a constant voltage from the battery charger is applied across the battery during its normal operation to keep the battery approximately in fully charged condition. In normal condition the battery charger supplies the substation load and also compensate the losses in the battery. But in case of heavy demand during simultaneous operation of many switch gears, the battery and the charger, are combined to supply the demand.
12. During normal floating condition the cell voltage, specific gravity and temperature of pilot cells should be measured daily to follow up the condition of battery as a whole. But the same readings of each and every battery cell should be taken at least once in the month to keep monitored the conditions of individual cell.
13. The battery should be refilled with fresh electrolyte once in three years interval to maintain the battery in proper operating conditions.
14. This is should be noted that, the pilot cell of a battery bank is one arbitrarily chosen battery cell which is used to get the information about overall condition of the battery. But one pilot cell must be fixed for one month and it should be changed in next month.
15. This was a brief description of maintenance of substation battery but it is always preferable also to follow the instructions given into the maintenance manual supplied by the manufacturer too.

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