PARTS OF A LEAD ACID BATTERY

A battery consists of a number of cells and each cell of the battery-consists of (a) positive and negative plants (b) separators and (c) electrolyte, all contained in one of the many compartments of the battery container. Different parts of a lead-acid battery are as under:

(I) PLATES: A plate consists of a lattice type of grid of cast antimonial lead alloy which is covered with active material. The grid not only serves as a support for the fragile active material but also conducts electric current. Grids for the positive and negative plates are often of the same design although negative plate grids are made somewhat lighter.

(II) SEPARATORS: These are thin sheets of a porous material placed between the positive and negative plates for preventing contact between them and thus avoiding internal short-circuiting of the battery. A separator must, however, be sufficiently porous to allow diffusion or circulation of electrolyte between the plates. These are made of especially-treated cedar wood, glass wool mat, micro porous rubber (mipor), micro porous plastics (plastipore, miplast) and perforated PVC, as shown in Figure In addition to good porosity, a separator must possess high electrical resistance and mechanical strength.

(III) ELECTROLYTE: It is dilute sulphuric acid which fills the cell compartment to immerse the plates completely.

(IV) CONTAINER: It may be made of vulcanized rubber or molded hard rubber (ebonite), molded plastic, ceramics, glass or celluloid. The vulcanised rubber containers are used for car service, while glass containers are superior for lighting plants and wireless sets. Celluloid containers are mostly used for portbable wireless set batteries. A single mono-block type container with 6 compartments generally used for starting batteries is shown in Figure.

Full details of a Russian 12-CAM-28 lead-acid battery parts are shown in Fig. 9.3. Details of some of these parts are as follows:

(A) BOTTOM GROOVED SUPPORT BLOCKS: These are raised ribs, either fitted in the bottom of the container or made with the container itself. Their function is to support the plates and hold them in position and at the same time protect them from short-circuits that would otherwise occur as a result of fall of the active material from the plates onto the bottom of the container.

(B) CONNECTING BAR: It is the lead alloy link which joins the cells together in series connecting the positive pillar of one cell to the negative pillar of the next one.

(C) TERMINAL POST OR PILLAR: It is the upward extension from each connecting bar which passes through the cell cover for cable connections to the outside circuits. For easy identification, the negative terminal post is smaller in diameter than the positive terminal post.

(D) VENT PLUGS OR FILLER CAPS: These are made of polystyrene or rubber and are usually screwed in the cover. Their function is to prevent escape of electrolyte but allow the free exit of the gas. These can be easily removed for topping up or taking hydrometer readings.

(E) EXTERNAL CONNECTING STRAPS: These are the antimonial lead alloy flat bars which connect the positive terminal post of one cell to the negative of the next across the top of the cover. These are of very solid construction especially in starting batteries because they have to carry very heavy currents.

1. -ve plate
2. Separator
3. + ve plate.
4. + ve group
5. -ve group
6. -ve group grooved support block
7. Lug
8. Plate group
9. Guard screen
10. Guard plate
11. Cell cover
12. Plug washer
13. Vent plug
14. Mono-block jar
15. Supporting prisms of + ve group
16. Inter-cell connector

17. Terminal lug
18. Screw
19. Washer
20. Nut
21. Rubber packing
22. Sealing compound.

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