AGM batteries - differences, review of models, pros and cons, charging features

When and why did AGM technology appear?

The birth date of the first battery is considered to be 1860. Since then it has been constantly improved. The materials, dimensions, and design changed. Years passed, and even the best of the classic lead-alkaline batteries (EFB) ceased to meet the demands of the times. A unique and bold solution was required, both in the design and in the very principle of operation of the batteries. AGM technology (Absorbent Glass Mat - moisture-absorbing glass mats) owes its appearance to engineers from the American company Gates Rubber Company. Almost fifty years ago, it was they who proposed an alternative to the classic liquid battery.

Design features or what is an AGM battery?

The essence of the discovery is the complete abandonment of the liquid state of the electrolyte. It was replaced by a special woven material. In this case, a mixture of sulfuric acid and distilled water turns out to be bound by the structure of synthetic mats. It should be noted that the small pores of the material serve to retain drops of electrolyte, and the large ones (capillary forces leave them free) serve to circulate vapors that have not had time to condense in the battery cavity.

Note that in batteries with AGM technology, only highly qualified lead (degree of chemical purity) is used. Another innovation is the addition of antimony and calcium, which significantly extends the service life of the plates.

For its time, this engineering solution and the results of its tests turned out to be so outstanding that the battery using AGM technology was supplied for several years exclusively for the needs of the army and military aviation.

The difference between AGM and GEL batteries

Scientific progress does not stand still, and, apparently, that is why AGM technology once had a competitor - these are gel batteries. Their main difference from their predecessors is that the space between the lead plates is no longer filled with glass fiber, but with a frozen porous solution of sulfuric acid and silica gel. The latter acts as a thickener. It is in this structure of the mixture that the main advantages and advantages of gel batteries lie. This state of the environment effectively prevents the failure of the electrodes and, as a result, prevents the breakdown of the battery itself.

For reference

Destruction of lead plates is an inevitable result of the electrolysis reaction. And if this is so, then slowing down this process and preventing internal closure of the circuit is the main task that scientists have been working on since the invention of the battery. A significant disadvantage of gel batteries is their increased sensitivity to temperature. So already at 100-110 degrees the mixture of acid and silica gel loses its working condition. At the same time, the ability of the gel to retain sulfuric acid vapor decreased. All this ultimately affects the rigidity of the structure as a whole.

Among AGM batteries there is an internal division into types. About a third of their total number has spiral matting. This technical solution allows you to maximize the area of ​​the chemical reaction, but at the same time dimensions and weight are sacrificed. In addition, exclusive rights to the “spiral” in batteries are patented, which significantly affects their popularity. As for plate batteries, this type of battery is the leader among motorists’ preferences. We also note that the peak of their popularity is still ahead, and the number of companies that produce AGM batteries is expanding every day.

So what is the basis of VRLA?

Once upon a time, regular evaporation of liquid caused the exposure of metal particles of the electrodes, as well as the active destruction of lead particles.

To minimize such a deadly impact of aggressive factors, current devices are made maintenance-free.

This means that in such mechanisms it will not be possible to simply open the lid and pour liquid.

The best example is a technology called AGM VRLA. Translated into Russian, this means an acid battery equipped with the necessary adjustment valve.

These batteries are manufactured in a completely impermeable case, but with the help of a special fuse, the risk of damage to the battery is eliminated if excessive pressure suddenly appears.

Despite the connection with the atmosphere through a specific valve hole, such a device does not require special maintenance, since water evaporation occurs extremely rarely.

For example, in the case of regular use, this locking mechanism remains closed.

However, if you forget about the activated charger for a long time, then a small amount of liquid from the electrolyte can leak through the open hole.

The specific characteristics of the above described device can be implemented through the use of different technological approaches. AGM VRLA Battery VRLA AGM are primarily sealed batteries.

The so-called AGM technologies were used in the manufacturing process of their plates.

These devices have a significant shelf life, which is explained by the presence of a special fiberglass layer that can absorb electrolyte well, while protecting the plates from shedding. As for VRLA GEL, we are talking about a gel battery.

Review of AGM batteries from different manufacturers: characteristics, prices, differences

Today, batteries using AGM technology can be found literally everywhere. They are used on assembly lines to equip cars equipped with a start-stop system. They operate barriers, blinds and gates. Thanks to rechargeable batteries, neon advertisements and road signs on highways glow at night. Let us add that AGM technology is recognized as optimal in batteries of power plants operating on energy sources such as the sun, wind and waves. Beyond competition, the advantages of AGM also turned out to be in uninterruptible power supplies for computers. Currently, almost all well-known global brands have devoted significant parts of their production volumes to AGM batteries. These are BOSCH, and Optima, and Tudor, and Medalist and others. Below, for comparison, are several popular models of car batteries with AGM technology and their characteristics.

Table 1. Comparative review of AGM batteries

It is gratifying that recently Russian-made batteries have become increasingly common in ratings of the top companies in the use of AGM technology in batteries. In addition to markings indicating the type of battery, you can often see on battery cases: VRLA (Valve Regulated Lead Acid batteries) or SLA (Sealed Lead Acid batteries). These inscriptions are required according to international safety standards.

The first abbreviation is usually placed on batteries with a capacity of over 30 Ah and indicates that the device is equipped with a safety valve. The second marking is placed on low-capacity AGM batteries (up to 30 Ah). The presence of a bypass is due to the inevitable release of hydrogen during recharging. When the value reaches 100 millibars, the valve opens and releases gas into the atmosphere, thereby relieving the pressure to a safe level.

Pros and cons of technology

Note that AGM battery technology is far from ideal, as are the power sources themselves. Therefore, along with undeniable advantages, they also have some disadvantages.

Advantages:

• This type of battery does not require maintenance. This means that their care is reduced to a minimum;
• Has a large starting current. So, compared to acid batteries, it is 50-75% higher, which is invaluable when starting in the cold season;
• Not afraid of deep discharge. Even an average AGM battery must cope with at least two hundred full discharges (to zero), at least five hundred battery discharges up to 50% and a thousand that reduce the capacity by 20-30 percent;
• Allowed for transportation and operation in almost any position;
• The service life of AGM is from 5 to 12 years (subject to mandatory compliance with charging rules);
• Neutral to high ambient temperatures (for example, in the engine compartment of a car). This puts them in rank above all classic and most gel batteries.

Flaws

• Increased weight;
• The AGM battery is significantly more expensive than any of its competitors among lead-acid batteries;
• Specific chargers required;
• Requires caution and attention when charging, as well as when operating on vehicles not equipped with a recharge relay.

Important! AGM technology batteries cannot be taken as a panacea for all possible ills. This type of battery is very vulnerable to overcharging. This means that if the car is not equipped with a device that prevents excess charge, you should refrain from purchasing such batteries.

Advantages and disadvantages

Batteries manufactured using the technology described above have a number of advantages over traditional batteries that arise from the use of this technology:

1. The first plus is an increased level of resistance to vibrations in the car, which allows you to increase the service life as a whole.
2. The car owner no longer needs to maintain the battery.
3. The device can be installed in any position convenient for the motorist. Mounting the device upside down is prohibited for safety reasons since the valves are located at the top.
4. Another advantage is that the battery device itself is completely sealed and equipped with valve regulation. Accordingly, the likelihood of corrosion at the terminals, as well as leakage of working fluid, is very low.
5. Recently, battery manufacturers are increasingly claiming increased device performance and inrush current levels.
6. The device itself is considered safer than traditional batteries. If you charge the battery correctly, the likelihood of gas emissions and, accordingly, the likelihood of an explosion will be very small.
7. The last plus is that the batteries can operate with confidence even at the lowest temperatures (up to 30 degrees below zero). If the air temperature is lower, then there is a possibility of crystallization of the electrolyte in the case of a completely or partially discharged battery. Accordingly, this may lead to a reduction in service life, but for regions with moderate temperatures such batteries are excellent.

Of course, devices of this type cannot have only advantages, so now let’s move on to the disadvantages:

1. The first drawback is that the device is too heavy.
2. Another disadvantage is that batteries of this type cannot be stored in a discharged state. If the voltage level decreases and is less than 1.8 volts, this may lead to a decrease in service life as a whole.
3. These devices, as practice shows, are very sensitive to excess voltage; of course, this is a drawback.
4. As practice shows, an important disadvantage is that when operating at low temperatures, the battery can quickly discharge, especially if heavy loads are placed on it. This disadvantage generally applies to all lead-acid devices.
5. According to manufacturers, such batteries typically provide up to 500 complete discharge and charge cycles. However, in fact, as shown by the results of tests of batteries from various manufacturers, this figure can be 100 cycles, and in some cases it even reaches several thousand.
6. In general, this type of battery is hazardous to the environment because it contains lead oxide.
7. Compared to traditional batteries, the cost of such devices is much higher.

Requirements for the charging process and chargers

As already mentioned, AGM and GEL batteries are quite resistant to maximum discharge. Excessive current and voltage can cause much greater damage to them. The optimal current for charging is considered to be one whose value is 10% of that indicated on the battery itself. For example, an AGM battery with a capacity of 32 Ah should be charged with a current of 3.2 A. This means that the charger (ideally) must have the function of adjusting the current and voltage. For a more detailed consideration of the technology for bringing the battery into working condition, we will describe the process point by point:

• We connect the charger and set the nominal voltage on it, and set the current to “0”;
• We connect the wires according to the system: minuses - to minuses, and pluses - to pluses;
• We set the current value to 10% of that indicated on the battery;
• We observe the process. During its normal course, the voltage should increase and the current strength should decrease. When the value of the latter drops to values ​​close to zero, the AGM battery will be charged.

Important! Charging an AGM battery with a higher current will significantly reduce the charging time, but may also harm the battery. Therefore, you should resort to this regime only in exceptional cases!

Regarding the chargers themselves, we note that there is enough choice on the Russian market to choose the best option. You can choose a universal one - with adjustment of current and voltage, or you can get by with a highly specialized one, where the current strength is fixed (0.1A, 0.2A, 0.3A, and so on). The price range for “chargers” is from 1,500 to 12 thousand rubles.

Features of AGM battery charging

Before we tell you about all the pros and cons of GEL and AGM batteries, we suggest you learn how to properly charge your device using a charger. The procedure for charging batteries of GEL and AGM types is carried out only using a charger, taking into account all the requirements for the charger and battery. It should be noted that for GEL and AGM devices only special charges with appropriate indication for all parameters are used. This refers to both voltage and current, that is, the charger in any case must control these indicators.

AGM device cross-section

When the battery charging procedure is carried out, the system strictly controls the temperature level of the electrolytes. If the temperature level is more than 45 degrees, then it is no longer acceptable, since it may subsequently lead to accelerated breakdown of the battery. For the same reason, a GEL or AGM battery should not be located in the engine compartment while charging. The peculiarity of restoring charging in batteries of this type is to stabilize the level directly by voltage, and not by current. Accordingly, this principle makes it possible to prevent gas formation inside the system.

Let's look at the charge restoration procedure using the example of a BMW vehicle:

1. The battery charging voltage level for vehicles of this brand should be no more than 15.2 volts.
2. The most optimal voltage when restoring a battery is between 14.4-14.8 volts, but here you need to rely on the data in the service book for a specific car model.
3. The temperature level of devices during recovery should be within 15-25 degrees Celsius.
4. The battery can be considered fully charged only when the charging current drops below 2.5 amperes.
5. If you have to charge the device at lower temperatures, then you need to complete the procedure when the charging current drops below 1.5 amperes (the author of the video on how to properly charge a device at home is madebyme).

One step away from choosing

Solid service, extensive driving experience and excellent skill may remain useless if your car suddenly runs out of power. That is why it is quite natural for motorists to want to have the best battery in all respects. The closest to obtaining this status today are batteries using AGM technology. Now, we hope you know what it is. In this article, we talked about the features, compared batteries from different manufacturers, asked the price and received a certain amount of useful information. Years will pass, AGM and EFB technologies in car batteries will become history. They will be replaced by more advanced power sources. This will happen later, but the car needs energy today and now. To do this, you just need to make a choice between savings and reliability, some inconvenience and confidence. And don’t make a mistake in it - we hope this article will help you. Video on the topic: