LEAD ACID BATTERY EVERYTHING YOU NEED TO KNOW
You’d soon get cranky without one, says Fuzz
The humble car battery is often overlooked and regularly neglected, until it’s too late. Only then are its virtues appreciated. In the earlier days of the motor car, the battery’s duties were relatively humble, providing a reservoir of electrical power for basic lighting equipment and the ignition circuit although, in the latter case, the magneto provided self-contained spark generation. Starting power was down to the deft swing of a cranking handle, so the battery had a relatively easy life.
However, the motor industry quickly began to add such trinkets as electric start facilities, more powerful lighting and heaters with electrically powered fan motors. All of these required some form of stable electrical supply and so the battery became increasingly important.
Lead-acid batteries had been in existence for quite some time, with reasonable speed of chargeability, relatively long life and stability chief among their advantages. The dynamo was tasked with the job of keeping the battery charged, so as long as the car was bowling along at a decent lick without too many of the electrical trinkets being employed at the same time, battery charge could be maintained at a satisfactory level.
However, as driver expectations began to grow, more and more pressure was inflicted upon cars’ batteries and charging systems. Higher compression engines required ever greater cranking power and so battery technology had to develop in tandem, as did that of the charging system, with the alternator soon becoming the generation method of choice, thanks to its ability to charge at low engine revs.
In-car entertainment provided a further drain on battery power, as did computer-controlled and electrically-operated everything, and still the humble battery remained – and still remains – as the stable reservoir of power, all be it with updated materials and construction.
The basic principle of the battery remains the same as ever. Lead acid batteries do not generate their own power – they are a storage facility for generated electricity and so need to be charged in order for them to work, hence the initial charging of a battery and its continuous ‘topping up’ by a dynamo or alternator.
A 12-volt car battery typically consists of six cells, each with a charged capacity of 2.1 volts, giving an overall output voltage of 12.6 volts. Each cell consists of a positive and negative plate, in grid form, each of which is made from a lead alloy. The negative plate is coated with ‘sponge lead’ – compressed, finely divided lead. The positive plate is coated in lead oxide and between them is a layer of insulating material, with the whole submerged in an electrolyte solution of deionised water and sulphuric acid.
‘As expectations began to grow, more and more pressure was inflicted upon cars’ batteries and charging systems’