Among the characteristics of the battery there are many important parameters indicated in the passport and on the case. Their knowledge will allow you to choose the most suitable battery for your car.
Manufacturers producing car batteries are required to indicate in the passport all the main parameters of their product. Among them, in addition to capacity and voltage, there should be efficiency, service life, depth of discharge, permissible charging and discharging current, temperature range, dimensions and other characteristics. However, in practice, the consumer is only interested in a few of the most important parameters.
Capacity, voltage and charge
Capacity refers to the amount of energy stored in the battery and is expressed in ampere-hours. For example, a 55 amp-hour battery can hold a 1 amp load for 55 hours. But it must be borne in mind that with an increase in the load, the battery capacity will fall. One charge-discharge period is called a cycle. Usually, batteries are used that painlessly allow a discharge of 5-10% of the capacity (then you need to charge again). If the battery allows a discharge of more than 50%, then such products are called deep discharge batteries.
The next parameter is voltage. It varies greatly in no load, charging, discharging. The voltage value can be used to judge the state of charge of the battery. Conventional starter batteries with a liquid electrolyte, under the condition of no load, should produce from 12.5 to 12.7V. At the terminals of sealed batteries (for example, helium), the voltage should be within 13-13, 2V. At the same time, these values are usually valid at a temperature of + 20-25C (for more details, it is indicated in the product passport). The voltage is measured with a voltmeter 3-4 hours after the load is disconnected and in the absence of charging current.
It is possible to accurately determine the degree of charge, expressed as a percentage, only by means of chargers with microprocessors and memory. Similar equipment is available in specialized workshops. Therefore, in practice, they use a hydrometer - a device that determines the density of the electrolyte. For example, in a lead-acid battery, 100% charge corresponds to a density of 1.265 at a voltage of 12.7V. At an electrolyte density of 1, 19, the state of charge will be 50%.
Dimensions (edit)
This is also an important characteristic considering the variety of modern cars. In Russia, the most common European type of battery with a height of 175-190 mm, on which the terminals are located in the corners. The Asian type of enclosure can be 220-230 mm high with a central location of the terminals. The American case is distinguished by the lateral arrangement of the terminals.
