Storage battery (accumulator battery). Purpose, device and types

10.2.1 Purpose of the battery

The battery pack provides electricity to all consumers while the engine is not running or running at very low speeds. It is also a backup power source case of a generator failure.

Attention
In case of failure of the generator it is not necessary to delay with its repair. It is necessary to solve the arisen problem right away. Prolonged use of only the battery pack can disable it, and at the most inopportune moment.

One of the main functional purposes of the battery is to start the engine with a starter.

10.2.2 Battery device

Chemical energy is converted into electrical energy inside the battery pack. The chemistry lies in fact that two plates consisting of lead were placed in a solution of sulfuric acid, on which clips were made (Figure 10.1). Two wires from the generator are connected to the clips. They start rotating it so that it emits electric current and charges the battery (while the battery is charging, it is a consumer of current). In this case, the electrical energy was converted into chemical energy - the battery was charged. In case if we disconnect the generator from the clips and connected, for example, a light bulb, and it will light up! It is so, because the process of converting chemical energy into electrical energy has begun. The benefit of this design is that the charging and discharging processes can be performed repeatedly. And in case if one follows the basic, fairly simple, rules of operation of the battery, it can last a long time.

The simplest battery consists of two plates that are placed in a housing (also called a battery cell). This housing is filled with a solution of sulfuric acid (which is called an electrolyte) and closed on top with a cover. This cover has holes, through which two clips come from each of the plates (positive and negative).

Figure 10.1 Battery pack operating principle.

Any battery pack consists of several (often six) simple batteries described above. Why exactly six? The car's on-board network is designed for 12 V, which means that the battery pack must produce the same. Due to its size, one cell (two plates) provides a voltage of approximately 2 V. In order to obtain 12 V positive and negative plates are connected in series and make two common clips - positive and negative (see Figure 10.2).

Note
The battery pack must have such a size that it shall fit optimally into the limited space of the car's engine compartment.

Figure 10.2 Battery pack arrangement.

Many modern cars have a kind of protection for preventing theft of the audio system head module, which blocks the audio receiver after disconnecting the negative terminal from the battery. For the radio to work, one shall enter a certain code - the key. In case if you buy a new car, this code will be handed to you in the automotive dealership. In case if you buy a used car, you shall check with the owner the presence of such a code.

Note
It is worth mentioning that in some modern cars, after disconnecting the battery and reconnecting it, the on-board computer may display an error message. This message can be reset with the help of specialized equipment at the service station.

10.2.3 Battery types

According to the principle of the need for maintenance, battery packs are divided into serviceable and maintenance-free. Low-serviceable battery packs have become one of the subtypes of serviceable ones. At the moment, the use of serviceable battery packs is minimized. The names of the types of battery packs speak for themselves.

Liquid electrolyte is the basis of the lead-acid battery packs that are discussed in this chapter. However, battery production technology has come a long way. Nowadays you can often find batteries that are made on the basis of AGM technology, in which the electrolyte itself is absorbed in the glass fibers. One should also not forget about the increasing popularity of AMG (gel) battery packs (GEL), in which the electrolyte is thickened using silica gel to a gel state.

Due to the great variety of battery pack types, there has been much controversy about the effectiveness and durability of each. In essence, there is no one battery, which is ideal for all operating conditions. For, in case of winning in one thing, any type of battery pack definitely loses significantly in something else. For example, very popular maintenance-free "calcium" batteries have very low self-discharge rates and do not require any attention. At the same time, they are very "afraid" of deep discharges (as an example, with repeated short trips in the winter). In case of such discharges, this type of battery pack will become unusable in a very short period of operation. Low-maintenance battery packs are not affected by deep discharges. They instead require regular topping up with distilled water (on average, once every six months).

Note
Electrolyte boils during battery pack charging. But this is boiling not in the everyday sense of the word. Simply happens a splitting of water into oxygen and hydrogen (bubbles are created). The component of the electrolyte - water - boils, and the density of the electrolyte, respectively, increases. Distilled water is added in order to bring the electrolyte density back to normal.

Note
Release of hydrogen from the electrolyte is one of the significant dangers during the planned charging of the battery pack. It seems to be insignificant, but though it can explode. Therefore, all precautions shall be observed while servicing and operating the battery.

10.2.3.a Battery polarity

Polarity indicates the location of the negative and positive terminals of the battery. Polarity can be forward and reverse.

Note
In order to find out the polarity of your battery pack, set it to the side closest to the clips. Find out which of the pins is marked with a "+" and which is marked with a "-". In case if "+" is on the left, then the polarity is direct, if on the right - reverse.

10.2.3.b Rated capacity

Available capacity (designated as C20) is the amount of electricity (in A · h), which the battery pack can provide in a 20-hour discharge current with a current numerically equal to 0.05 of the rated capacity to a voltage at the terminals of 10.5 V at an electrolyte temperature of 25 °C.

Note
One shall always remember that it is necessary to install the battery pack of that capacity on the car, which is specified by manufacturer of the vehicle. Actually, nothing bad will happen. And the first time you will be happy to quickly start the engine. But do not forget that the possibilities of the generator are not limitless, and the operating conditions of the car can be very harsh. As a result, the larger capacity battery will be constantly short of energy for recovery. It will not be charged to 100%, which will soon lead to its failure.

10.2.3.c Reserve capacity

Reserve capacity (designated as Cr) is the discharge time in minutes of a fully charged battery with a current of 25 A to a voltage of 10.5 V at an electrolyte temperature of 25 °C.

Note
Reserve capacity is 1.63 times greater than the available capacity in numerical terms (for example, for a battery pack with a capacity of 55 A · h it is approximately 90 minutes). This is the time during which a fully charged battery can provide electricity to the minimum number of consumers that are required for safe driving in case of a generator failure.

10.2.3.d Cold cranking current

Cold cranking amps (CCA) (Iх.п.) - according to GOST (DSTU) 959-2002 - is the discharge current that the battery is able to provide at an electrolyte temperature of -18 ° C for 10 seconds at a voltage of at least 7.5 V. The higher this parameter, the better the engine will start in winter. However, due to the increase in the load on the starter, its life span may decrease.

Note
The value of the cold cranking amps depends on the method of its measurement. An approximate correspondence of the values of the cold cranking amps, defined by different standards, is provided in the table below.

10.2.3.e Density of battery electrolyte

Density of the electrolyte is one of the main indicators that characterize the operating state of the battery pack. It shall always be within a certain range. In case if the battery pack is of low-maintenance type, then in summer the density is slightly reduced. But in winter it increases in order to eliminate the possibility of freezing of the electrolyte.

Note
The density of the electrolyte is measured by a special device - a densimeter.

10.2.4 When buying a battery

Let's say you decided to replace the power supply. You went, for example, to an auto parts store, decided on a model. Now be more careful. Ask first for a dry-charged battery (without electrolyte) or filled with electrolyte and charged. In the first case, the shelf life should not exceed three years, in the second - six months. Look at the date of manufacture of the battery pack and, if more than one year has passed since the date of manufacture, perform the following checks, if possible:

• inspect the casing for damage;

For filled in and charged batteries:

• determine the level of electrolyte. It should be between the "min" and "max" marks (translucent plastic casing) or be higher by about 15-20 mm from the upper end of the plates;
• check the density of the electrolyte. It should be 1.25-1.26 g/cm3 at 25 ± 5 °C;

BATTERY PACK MARKING

Figure 10.3 Battery pack marking according to domestic standard.

Figure 10.4 Battery pack marking according to European standard EN 60095-1.

Figure 10.5 Battery pack marking according to US standard SAE J537.

For all

• the color of the charge indicator (if available) should be green;
• the voltage at the unloaded terminals shall be at least 12.6 V.

Note
One way or another, there shall be operating manual in Russian or Ukrainian and a warranty certificate with the specified warranty conditions.

Feel free to require the seller to perform the checks described above, because the car battery pack is not the battery for the CD player. It is not purchased for one month, and the operation of all electric systems of the car depends on its quality.