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A car battery (AKB) is a device that is used as an additional source of electricity in the car’s onboard network, when the engine is turned off, as well as for starting it. In the cold season, the quality of the battery is subject to higher requirements.

The main components of the battery: the body and cells (cans), where packs of lead plates (electrodes) are installed. On these plates, the active mass – the main reagent in the battery’s operation – is applied. The electrodes are separated by separators to prevent them from shorting to each other.

Type of Battery

Traditional (lead-acid) – contains lead electrodes and electrolyte (sulfuric acid). It has a low price, no “memory effect”, resistance to low temperatures, low self-discharge. At the same time, traditional batteries are sensitive to shaking and overturning, need maintenance. Such batteries have become obsolete.

Low antimony (Sb/Sb) – the electrodes are made of lead with low antimony content (2.5-3% vs. more than 5% in traditional batteries). The battery is resistant to deep discharges, surges in the network, costs inexpensive. Self-discharge and water consumption of Sb/Sb battery is lower than that of lead-acid battery but higher than that of calcium battery. Disadvantages: maintenance required, high self-discharge rate.

Calcium (Ca/Ca) – electrodes are made of lead with the addition of calcium. Such battery is characterized by resistance to vibration and corrosion, and self-discharge and water consumption of such a battery are minimized (maintenance-free). A calcium battery is more expensive than the low-magnesium one but cheaper than gel and AGM batteries. The disadvantage – the battery does not withstand a deep discharge.

Important: if allowed to deeply discharge such a battery, it will be difficult to recharge it (after 3-4 such discharges, the battery fails).

Hybrid (Sb/Ca, Hybrid) is a combination of two previous types: positive electrodes are low-antimony (1.5-1.8% antimony, 1.4-1.6% cadmium), the negative ones are lead-calcium. As a result, such a battery is resistant to deep discharges and is characterized by low water consumption (maintenance-free). Minus – high cost.

Silver-calcium (Ca/Ag) – electrodes are made of lead-calcium alloy with the addition of silver. The battery has an increased resistance to deep discharges and corrosion, while maintaining all the advantages of a calcium battery (maintenance-free). The disadvantage is a very high price.

Sealed lead-acid (SLA, VRLA) – in contrast to traditional models does not contain liquid electrolyte. Such a battery does not need maintenance, is resistant to deep discharges, but it is expensive.

There are two types of batteries:

AGM (absorbed electrolyte) – has a microporous plastic separator impregnated with electrolyte. AGM is cheaper, more resistant to vibrations, flips, low temperatures, short circuits. In addition, such model supports the start-stop system. The battery has a shorter service life, discharges itself more quickly and is less able to withstand a deep discharge.
Gel (GEL) – the electrolyte is not liquid, but gel-like. It lasts longer, has less self-discharge and is better able to withstand deep discharges. Disadvantages: sensitivity to overcharging, overheating, low temperature and short circuits, higher cost than the AGM.

Basic supply

Dry-charged – due to the absence of electrolyte it is stored for a long time (3-5 years) without changing its properties. To make such a battery in working condition, you need to spend money (to buy electrolyte) and time (charging the battery).

Filled – contains electrolyte, does not require any expense to bring it to working condition and is immediately ready for use. It is better to buy just such a battery.


Servicing means a periodic refilling with distilled water to check the electrolyte level.

Serviceable is cheap and repairable: provides for replacing individual jars as they fail. This battery allows discharging and recharging each can to restore its properties. At the same time, such a model discharges quickly and requires frequent maintenance. Such batteries are already outdated and are rare.

Low-maintenance – combines a moderate price and good performance. Such a model is serviced once every six months to a year. The low-maintenance battery is only partially repairable and does not provide the ability to discharge and recharge a separate can. These models are used most often.

Maintenance-free – requires no maintenance (works 5-7 years), but this advantage has a downside: high cost, sensitivity to deep discharge, resulting in reduced capacity. In addition, such models do not tolerate low temperatures and prolonged downtime.


This refers to the amount of energy a device gives off as it discharges over a certain period of time. The rated capacity is measured in ampere hours (Ah).

A 60 Ah battery will deliver 1A for 60 hours or 2A for 30 hours. The higher the capacity, the more attempts the driver has to start the engine and the longer the car’s electrical equipment will last when the engine is off. At the same time, as the battery capacity increases, so does the weight. Therefore, find the best balance for your particular case.

The requirements for battery capacity depending on the type of vehicle:

  • up to 20 Ah – motorcycles;
  • 40-100 Ah – passenger cars;
  • over 100 Ah – buses and other heavy vehicles.

Important: When choosing the optimal battery capacity, be guided by the technical characteristics of the vehicle.

The battery capacity is influenced by the type and displacement of the engine. For example, for a car with a petrol carburetor engine capacity of 1.2-1.8 dm3 the battery capacity is 55 Ah; for the same engine capacity of 1.8-2.5 dm3 – 62-66 Ah, for the engine capacity of 2.5-4.5 dm3 – 75 Ah.

Gasoline injection and diesel engines have different capacity parameters with the same working volume. More detailed information can be found in special tables.

Do not choose a battery with a lower capacity than recommended by the manufacturer for a particular car. In certain operating modes of the engine (idling) and small daily mileage of the car, the battery on a par with the generator feeds the electrical equipment.

In these cases, the battery of low capacity discharges quickly (depth of discharge – 40-50%). This is critical to its performance and will lead to a reduction in service life.

You should distinguish between the nominal and reserve capacity of the battery.

Nominal – the capacity equal to 20 hours of discharge (indicated in the passport and label of the battery). For a 60 Ah battery, the discharge current is 3A.

Reserve – the value that means the time of powering the electrical equipment of the car with a current of 25A when the generator is not running. Thus, the reserve capacity of a 60 Ah battery is equal to 95-100 minutes.

Starting current

Starting current or cold cranking current is the amount of current supplied to the starter to start the car engine. This parameter is measured according to several standards (EN, DIN, SAE): the current that the battery delivers at a temperature of -18°C for a certain time without the voltage dropping below a set value.

Starting current standards:

  • European (EN) – discharge to 7.5 V for 10 seconds;
  • German (DIN) – discharge up to 9 V for 30 seconds;
  • American (SAE) – discharge to 7.2 V for 30 seconds.

The more massive the vehicle, the higher the starting current of the battery must be. A battery with a higher starting current will start the engine better in winter, but the load on the brush-collector block of the starter will increase, which reduces its service life.

Important: the optimal starting current parameter is usually specified in the vehicle specifications. When replacing the battery (if this value is unknown), buy a new device with a starting current not less than the old one. If the cold cranking current is below the recommended value, the engine may not start in winter.

Terminals AGM


The design of the terminals affects the compatibility of the battery with a particular car model.

Cone – there are no own clamps, and special clamps act as fasteners. This terminal design is used in European (Euro) and Asian (JAP) cars.

Pay attention to the features of the cone terminals:

  • Euro – the thickness of the plus contact is 19.5 mm, minus – 17.9 mm. Terminals are “recessed” in special niches, which reduces the risk of short-circuiting the battery cover down or falling on the top panel of various objects.
  • JAP – thickness of positive contact is 12.7 mm, negative – 11.1 mm. The terminals are elevated above the top panel (cover) of the battery.
  • Screw terminals (USA) – clamps with internal threads are used instead of clamps. Similar terminals are used in American-made cars.

Important: with the help of special adapters, you can achieve compatibility of the Asian battery with the European car. But in the opposite case – mounting a European battery on an Asian car – as a rule, without replacing the fasteners is not possible.


Polarity is the position of the terminals on the battery (determined by the “plus” terminal). The “+” terminal is either on the left or right (for cars made in Europe). There are also universal models that are made with both left and right plus (some Asian cars).

Important: To determine the correct polarity of the battery, turn the battery with the front side (label) facing you. After that, find the side where the terminal with the “+” sign is located.

Commonly used names for polarity are: straight (“+” on the left), reverse (“+” on the right).

For trucks, the “+” position on the left side is considered the European standard, while the right side is for Asia.


Most often, the terminals are placed on the top panel (standard). There are also lateral (for buses and trucks) and diagonal (for heavy equipment) placement. Batteries are very rarely used with the terminals placed centrally.


The amount of current voltage that the battery supplies to consumers.

  • 6 V – for very light motor vehicles;
  • 12 V – standard value for most vehicles (cars, trucks, motorcycles, heavy equipment);
  • 24 V – for trucks and other equipment with diesel engines.


The length, width and height of the battery depends on the location of the device. In order not to make a mistake, tell the seller-consultant the technical parameters of the car. This will help you find the right battery from the catalog. Even better – take the old model with you, but in some cases it is inconvenient because of the large weight of the battery.

Date of manufacture

The average life of a battery does not exceed 5 years. This means: the less time has passed since manufacture, the longer it will last. Remember that a battery’s life is counted from the moment it is filled with electrolyte, not from the moment it begins to be used for its intended purpose.


The characteristics of the battery are indicated by its marking:

  • The first digit – the number of cells (3 or 6), defining the battery voltage – 6 and 12 V, respectively;
  • ST – “starter”;
  • second digit – capacity (Ah);
  • A – total cover;
  • H – flooded battery (dry loaded battery is not marked with a letter);
  • T, E – case material (thermoplastic, ebonite);
  • P, M – material of the separator (polyethylene, polyvinylchloride).

For example, the marking 6 ST-90 Az means that the battery consists of 6 cells and has a rated voltage of 12 V, is a starter battery, its rated capacity – 90 Ah at 20 hours of discharge. The battery is made in a monoblock with a common cover, the basic delivery – poured.


It is worth paying attention to the climatic and road conditions in which the battery is used.

At low temperatures, the operation of the battery deteriorates due to the increase in the viscosity of the electrolyte: the current supply time for starting the motor is reduced, the battery is charged more slowly, and the starter requires more time to start the engine than at high temperature. Therefore, to operate in such conditions, it is worth buying a battery with a capacity 5-10 Ah higher than that recommended by the manufacturer.

When driving off-road and on rough roads, the battery is subjected to strong vibrations and shocks. This can lead to a decrease in battery capacity and short circuit. If your vehicle is used in such conditions, look for a battery made with special extra plate locking technology (HEAVY DUTY). As a result, the risk of a short circuit will be reduced.

Equipped with

Charge indicator – shows the level of charge at the moment. This option allows you to judge the condition of the battery without resorting to special diagnostics. In some batteries, the indicator informs about the necessity to add water to the electrolyte.

Start-stop support – this mode switches the engine off during short stops and starts it up quickly. This saves fuel and reduces toxic emissions. On the other hand, it does serious damage to the battery. Start-stop support makes it possible for the battery to function normally in this mode.

Carrying handle – makes it easier to transport the battery.

Selection tips

  • The best option is to buy the device from a specialty store. Give preference to well-known brands that guarantee the quality of their products. Do not skimp on the battery, because it is purchased for several years.Inspect the battery: the body should be free of roughness, damage (including dents, cracks, chips) and dirt. It is good if the battery is in its original packaging.
  • On the case must specify the country of manufacture, the manufacturer and the date of manufacture of the battery, and the device itself is accompanied by a technical passport.
  • The warranty period for the battery: minimum – 6 months, famous brands give a warranty of 1-3 years.
  • An eloquent detail – protective caps, which are not found in fake devices.
  • If you buy a flooded battery, pay attention to the electrolyte level: in high-quality battery it covers the top edge of the plates.
  • It is advisable to measure the battery voltage with a multimeter: it should be 12.6 volts. If this parameter is lower, the battery is old or damaged.

Tips for use

  • It is strictly forbidden to turn over even a dry battery.
  • Always be aware of the battery’s state of charge. The lower the charge, the faster the life of the battery decreases. Charge the battery at least once every six months. Do not use a discharged
  • The battery in the fall and winter, as the battery will be under more strain at this time.
  • Clean salt deposits from the terminals at regular intervals to prevent the battery from discharging itself.

What is an AGM battery?

Technically speaking, the AGM car battery is the same lead-acid product that many generations of motorists are used to, but it is much more advanced than its ancestors and will soon completely displace them from the market.

AGM (Absorbent Glass Mat) is a technology for manufacturing batteries with absorbed electrolyte, which is impregnated with micropores of the separator. The free volume of these micropores is used by the developers for closed recombination of gases, thereby preventing water from evaporating. The hydrogen and oxygen leaving the negative and positive plates, respectively, enter the bonded environment and recombine, remaining inside the battery. The internal resistance of such a battery is lower than that of its “liquid” predecessors because the conductivity of the fiberglass separator is better compared to traditional polyethylene “envelopes”. Therefore, it is able to deliver higher currents. The tightly compressed plate pack prevents the active mass from crumbling, which allows it to withstand deep cyclic discharges. Such a car battery can work even upside down. And if it is smashed to pieces there will be no poisonous puddle even in this case: the bound electrolyte must remain in the separators.

Today’s applications of AGM are cars with a start-stop mode, cars with increased energy consumption (EMERCOM, ambulance), etc. But tomorrow the “simple” car battery will slowly fade into history…

Are AGM and conventional batteries interchangeable?

The AGM car battery is 100% interchangeable with a “conventional” battery. Whether such replacement is necessary, if the car has enough good regular battery is another question. But the reverse replacement, of course, is incomplete – it can be used in practice only in a hopeless situation and as a temporary option.

Is it true, that you can use AGM 50 Ah car battery instead of the usual 90 Ah one?

That is, sorry, nonsense. How can you almost halve the charge and say there is no difference? No technology, not even AGM, will compensate for lost ampere-hours.

Is it true that a high current AGM battery can ruin a car’s starter?

Certainly not. The current is determined by the resistance of the load, and in this case, the starter. And even if a car battery can deliver a million amps, the starter will draw exactly the same amount of current as from a conventional battery. It cannot break Ohm’s law.

In what cars is it undesirable to use the AGM?

There is no such restriction. Even if we consider old cars with a totally faulty voltage regulator and unstable voltage in the network, even in this case, the AGM car battery will die not earlier than usual, but even later. The voltage limit, above which the troubles are possible, is about 14.5 V for conventional batteries and 14.8 V for AGM.

Which car battery is more afraid of deep discharge – AGM or usual?

Conventional batteries. After 5-6 deep discharges, they can finally “offend”, while for the AGM this number is practically unlimited.

Can an AGM car battery be considered completely maintenance-free?

This is a matter of established terminology, working more in favor of PR than science. Strictly speaking, the term is incorrect – both for AGM batteries and any other car battery. Only AA batteries can be called completely maintenance-free, but any lead car battery, in general, is not. Even the leader of technology – the AGM battery – is sealed, let’s say, by 99%, but not by 100%. And such a battery still needs to be serviced – to check the charge, recharge if necessary, etc.

How do gel batteries differ from AGM batteries?

At least in the fact that gel-type car batteries… do not exist! The question is generated by a well-established wrong terminology: gel batteries are used, for example, in electric forklifts or floor cleaning machines. The electrolyte in these, in contrast to conventional car batteries with liquid acid, is in a thickened state. In batteries with AGM technology, the electrolyte is bound (impregnated) in a special glass fiber separator.

Note that the most popular battery Optima is also AGM, but not a gel battery.

What is the reserve capacity of the battery?

This parameter indicates how long the car with a ruined alternator will last on a cold rainy night. The expert will say otherwise: for how many minutes the voltage at the battery terminals, giving a load current of 25 A, will decrease to 10.5 V. Measurements are carried out at a temperature of 25 ° C. The higher the result, the better.

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