Marine Engine Q & A- Electrical-Plate Construction,Electrolyte

Describe the plate construction of lead-acid battery.
Describe the eletrolyte reaction of lead-acid battery.

Plate Construction
A lead-acid battery is made up of a number of cells each with a nominal voltage of 2 volts Thus three cells separated by divisions ii common casing and connected in series make up a 6 volt battery, and six cells arranged in the same way make a 12 volt battery. Each cell has, say, seven positive and eight negative plates which are interleaved and arranged alternately positive and negative. Common practice is to have both end plates negative. Plates are prevented from touching by porous separators of insulating plastic; the design of the plates is such as to give the greatest possible surface area, adequate strength and good conductivity. The porous paste active material extends plate area to give maxi mum contact between active material and the electrolyte, and therefore good capacity. The oxide paste has little strength and is a poor conductor of so the deficiencies are made by a lead-antimony grid into which the taste is pressed.


Electrolyte
Sulphuric acid used to make .electrolyte for lead-acid batteries is, in its concentrated form. a non-conductor of electricity. In solution with water it becomes an electrolyte because of the break down of the H molecules into hydrogen (H+) ions and sulphate (SOˉ ˉ) ions as current carriers in the liquid.
Concentrated sulphuric acid has a great affinity for water and this, together with the heat evolved when they-come Into contact makes the production of electrolyte hazardous. A violent reaction results if water is added to concentrated sulphuric acid. Successful safe mixing is only possible if the acid is very slowly added to pure water while stirring .Normal the electrolyte is supplied ready for use in acid-resistant container.
Electrolyte is strongly corrosive and will damage the skin as well as materials such as paint wood, cloth, etc. on which it may spill it is recommended that electrolyte on the skin be removed by washing thoroughly (for 15 minutes) with water . Acid resisting paint must be used on battery room decks.