How to choose a car battery

A battery or car battery is an auxiliary source of electrical energy in vehicles with internal combustion engines. The battery starts the engine, feeds the on-board equipment when the engine is turned off: door locks, security systems, outdoor and indoor lighting lamps, a radio. And it also helps the generator, compensating for the lack of energy during peak loads.

How the battery is arranged

The battery accumulates and emits electrical energy due to complex electrochemical reactions, in which electrical energy is converted into chemical energy when the battery is charged and chemical into electrical energy when discharged, respectively. Basically, all starter batteries in question, according to the principle of the device and the active elements, are lead-acid. They consist of cells (cans) in which positively and negatively charged lead lattice plates are immersed in the electrolyte. An active mass is deposited on the plates, which holds the electrons. The cells are sequentially connected to each other.

Schematic representation of a car battery

To choose a battery suitable for your car, it is necessary to determine the main parameters by which the batteries differ from each other:

• battery type;
• voltage and polarity;
• container;
• starting current;
• dimensions;
• the need for maintenance;
• the form factor.

Battery Types

Lead-acid batteries by design (read — by the state of the electrolyte) are divided into the following types:

SLI (Start, Light, Ignition) Classic type, Fiamm Titanium Plus, Ista Classic, etc. — the electrolyte (a solution of water with sulfuric acid) is in a liquid state. Perhaps this is the most popular type of batteries, because they are installed on most cars at the stage of their production. Such batteries do not "like" deep discharges, while irreversible processes (sulfation) occur, negatively affecting the battery life. This type of battery is also more susceptible to temperature changes and mechanical influences, vibrations than others. The advantages of SLI include a relatively low cost in comparison with its technological competitors.

AGM (Absorbent Glass Mat) Varta Start-Stop Plus, Baren Polar Technik AGM, etc. — the electrolyte is impregnated with fibreglass, which fills the space between the plates. Such batteries are not afraid of deep discharges, they charge faster and are capable of producing high currents. They are installed on cars with engine shutdown systems at stops — Start-Stop, as well as a battery charging system with regenerative braking energy (Toyota, Citroen, Mercedes) and cars with increased energy consumption (special vehicles, executive cars). Their cost is noticeably higher than the batteries of the classic type.

EFB — (Enhanced Flooded Battery) Varta Blue Dynamic EFB, etc. — improved battery with liquid electrolyte. The peculiarity is that the plates are thicker and wrapped in special envelopes made of micro fibre. Both in terms of parameters and cost, this type is located between classic and AGM batteries. They have a higher starting current than the classics, they charge faster and have an increased cyclic resource. They are installed on cars with Start-Stop without regenerative braking system (VW, BMW, Audi).

GEL Platin Gel Energy, GS Yuasa Maintenance Free, etc. — gel-like electrolyte. Such batteries are more sensitive to low temperatures and charging voltage. When the temperature decreases, the capacity decreases more, and when the charge voltage is exceeded, the gel risks turning into a liquid and it will be impossible to return it to the reverse state. They are more afraid of short circuits than others. The advantages of gel batteries are a larger cyclic resource (and, accordingly, the battery life), a lower self—discharge level, they are not afraid of deep discharges. The price of gel batteries is higher than that of lead-acid batteries. They are often used in motorcycles, ATVs, and water transport, but they do not find mass use in motor vehicles.

The rated voltage is measured in volts (V). The first cars until the middle of the 20th century had 6V electrical equipment, modern passenger cars almost all operate on 12V, heavy trucks, military vehicles with diesel units can be equipped with 24 V equipment. Here the choice is simple – we take the battery only with the same voltage as the previous battery.

Polarity — the location of the terminals on the battery case. The plus (+) on the right is called "reverse polarity" or "polarity 0". Plus (+) on the left — "direct polarity" or "polarity 1". Pay attention to this indicator. Since, other things being equal, the battery of a different polarity will not be able to be connected — the conductive terminals simply will not reach the corresponding battery terminals.

The capacity (nominal) is measured in ampere-hours (Ah). It determines the estimated amount of energy that the battery stores (accumulates) and can give to the load (to consumers). Simply put, it is the number of attempts to start the engine. A battery with a larger capacity will allow you to perform a greater number of startup attempts, for example, at a reduced temperature, compared to the same battery with a smaller capacity. In determining this indicator, the most accurate adviser will be the experience of the engineers who developed your car, set out in the technical documentation (operating instructions, repair manuals, etc.). Choose a capacity not less than recommended for your car by the manufacturer.

The starting current (also called cold scroll current) is measured in amperes (A). This indicator characterizes the ability of the battery to "give off" current when starting a cold engine. In most standards (GOST standards for CIS countries, EN for the European Union, DIN for Germany, SAE for the USA, etc.), this value is determined at a temperature of -18 °C for 30 seconds. The difference is in the allowable final stresses, so the results differ from each other. And 440A according to EN will not be equal to 440A according to DIN or SAE. The higher the starting current and power, respectively, the more "confident" the starter wraps the crankshaft and starts the engine, especially in winter.

Owners of diesel cars need to pay special attention to this value — their car engines need more power to start than gasoline ones. According to this indicator, it is also worth focus on the technical documentation for your car. Since a smaller starting current may not be enough to start the engine on a frosty morning, and a larger one can significantly shorten the life of the starter.

Dimensions are the physical dimensions of the battery (length, width, height) in mm. The dimensions can be removed from the old battery and make a choice using accurate data. Also pay attention to the weight of the battery. Although modern technologies can reduce weight, at the same time, if the weight is significantly lower than analogues, it is worth considering how this saving is made. Often, high-quality batteries and weigh solidly.

Serviced/unattended. It depends on the battery manufacturing technology. Maintenance refers to the need to control the density of the electrolyte and top up the water if necessary (this applies to classic batteries). Prices for serviced batteries are lower than maintenance-free analogues, but they require periodic attention.

The form factor describes the design features of the battery, in particular the way the terminals are installed and their dimensions.

— European. A distinctive feature of European batteries are terminals that are somewhat "recessed" into the housing. Due to this, this form factor is considered safer than the Asian one — the risk of a short circuit is lower when the battery falls on a conductive surface or when a metal object hits it. In addition, the terminals themselves are usually made in the form of Euro cones. As the name implies, this form factor is found in cars of European manufacturers, mainly passenger cars.

— Asian. Asian batteries are easily identified by the terminals protruding above the upper part of the case; also, these terminals may be noticeably thinner than European ones, since many models use JAP cones (although not all). This option is popular with Japanese and Korean automakers, and is also quite widespread among trucks.

What affects the wear of the battery and how to understand that it's time to replace it

The red indicator on the instrument panel will inform that the battery requires technical assistance, and may need replacement

The reasons that affect the wear of lead-acid batteries are – service life, frequency and depth of discharge/charge cycles, the condition of the electrical equipment of the car (availability and correctness of connection of additional equipment), operating conditions (climatic, road conditions). At the battery device level, wear occurs for the following reasons:

• the sulfation of the plates, as we wrote earlier, is particularly intense during deep discharge;
• corrosion and shedding of the active mass of the electrodes, oxidation and dissolution of the electrode material in the electrolyte;
• insufficient mechanical strength or poor adhesion of the active mass to the electrode plates, which also leads to the shedding of active masses from the electrodes.

The fact that it's time to diagnose the battery, at least, will tell you the inability of the battery to start the engine. Often on cars with "tired" batteries, this happens with the onset of the first night frosts. Then the capacity decreases, and the current becomes insufficient to start the engine. Do not rush to get rid of such a battery, it should be diagnosed first. This can be done using special tools:

Checking the battery voltage using a multimeter

• the hydrometer will show the level of electrolyte density in the batteries. An indicator (the so—called "peephole") is installed on some of them, with which you can visually determine the degree of charge: green — order, yellow — low charge, black — the battery is discharged;
• the voltmeter will determine the rated voltage at the terminals;
• the load plug will show the voltage output under load;
• electronic testers will allow you to quickly and accurately determine the state of the battery, check it by several parameters at once and show the result on the display or display it on the computer screen.

Of course, these tools cannot be called easy to use, because a service specialist will help to assess the condition of your battery. Perhaps your battery can be charged and it will still serve, but it may also be that it will need to be replaced with a new one. By the way, used batteries are highly toxic waste. In order to preserve the environment and prevent its contamination, dispose of batteries only with the help of specialized enterprises.

Shelf life and service life

Batteries can be stored for a relatively long time, depending on the manufacturing technology (with the addition of antimony or calcium in the alloy of the gratings) for flooded batteries, this period may be 12-18 months. Perhaps even more for individual manufacturers and battery types. Dry-charged batteries can be stored for up to 3 years.

Before installing a new car battery of any type — check its voltage and charge it if necessary. During storage, the battery is spontaneously discharged, this process is called self-discharge and the actual voltage values, and hence the capacity, may be lower than the nominal ones. But the service life is a relative value, with the correct operation of electrical systems and the compliance of the battery capacity and loads on it, the average life of the SLI battery is about 4 years. AGM, EFB and GEL batteries have an increased resource.

Conclusions

A rechargeable battery is a device on the correct operation of which your confidence in the car depends. Pay due attention to the battery selection process, and then service and charge your battery, ensure it is clean in the engine compartment. Then it will provide you with a confident engine start and the operation of your car's electrical systems.