THE BATTERY

The battery stores up, by an electro-chemical process, the electrical energy provided by the dynamo (or by an external charging system) and feeds it as required to the ignition, lighting, starting and accessory circuits. A reserve of current is thus available when the dynamo is not charging— although it must be admitted that in the case of the compact type of battery fitted to most modern popular cars, the reserve is rather limited. For example, a fully-charged battery can become almost completely dis¬charged during the course of a long winter evening and night if the car is left parked with the side, tail, number-plate and panel lights switched on. Again, when the starter motor is struggling to turn over a cold engine on a freezing morning, the heavy load will cause a marked drop in voltage, thus starving the ignition coil and reducing the high-tension voltage available at the sparking plugs; and even a well-charged battery will deliver much less current when the temperature is near freezing point than at summer temperatures.