Winter takes toll on batteries

Press, 17 June 1988, Page 39

Winter takes toll on batteries

Ailing car batteries are likely to be failing at this time of the year, when the South Island winter bites. Cooler morning temperatures mean that more power is needed to start a car. At freezing point a car needs half as much power again to start as it does on a 27 deg. day. Therefore, batteries which have been struggling in recent months are now likely to be failing when you call on that extra starting effort. Battery efficiency falls off in the cold and weak batteries are more likely tn A fully-charged battery will not freeze until the fluid temperature drops to about —s7deg. A weak

one will freeze at —7 deg. Batteries produce electricity through a chemical reaction. This reaction can be reversed by passing current into the battery, thus recharging it. Batteries are made up of cells, each in fact a separate lead-acid battery. Each cell contains two lead frameworks, the plates. The positive piate is filled with lead peroxide and the negative with spongy lead. These plates stand immersed in sulphuric acid. The negative plate of one cell is connected to the positive plate of the next. The lead peroxide, lead and sulphuric acid react to form lead sul-

phate on the plates. The reaction creates electricity. However, when the plates are covered in lead sulphate the battery is flat. Car batteries are nearly all of 12 volts. Batteries must be the correct voltage for the car in which they are used, but this is not enough. Cars with bigger engines need more current to turn over the starter motor. The amount of current available depends on the amounts of each chemical in contact with the battery plates. Therefore, a large engine needs a large battery. Cars have charging systems which keep the battery charged. A bat-

tery’s reserves will quickly become depleted unless the charging system is working properly. Systems normally have an alternator or generator, and a voltage regulator. The alternator or generator is usually beltdriven off the crankshaft. The belt must not be allowed to become loose or the system may not be able to supply enough current. Fluid levels should be checked weekly. Batteries are recharged away from the car by connecting them to a battery charger which converts alternating current from the household supply to direct current, which is fed into the battery.