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AGM(Absorbent Glass Mat) – one of the types of lead-acid batteries, which is the development of the Gates Rubber Company (USA). First appeared in the 70s of the last century. Belongs to the class of unattended. Manufactured using a glass fiber separator between the plates.
Let’s talk separately about thermal acceleration and hybrid currents, BEM code, about the possibility of “lighting up” such a power source and other nuances of operation.
Difference Between An AGM Battery And Analogues
An AGM Battery is characterized by the presence of an absorbed electrolyte inside, which allows you to achieve better performance compared to standard – liquid types of batteries.
In simple words, between the plates of the product there are so-called “blotter mats” made of fiberglass. Electrolytic composition is absorbed into them.
Otherwise, AGMs are no different from classic batteries. They have the same characteristics, similar composition of the electrolytic fluid and plates.
In fact, these are the usual lead-acid batteries, but with a special approach to placing the electrolyte between the plates, and therefore there are some charging features.
What Causes Improper Charging
Mistakes in charging an AGM type battery can lead to negative consequences. It’s easy to explain.
The resistance of such batteries inside the mats is different, so the charging current in the car (even when controlled by a BMS) will increase excessively. In this case, areas of severe overheating may appear in the battery.
The water that is near such areas will evaporate, and the “extra” current, which is not involved in charging, activates electrolysis.
If you continue the process of incorrect charging, the AGM battery case overheats, becomes softer and “swells”. Vapors of electrolytic liquid escape from the battery, making their way through the valves.
If you do not see this problem in a timely manner, the battery will be destroyed, and the car itself may catch fire.
In addition, after such heating, it takes a long time for the power supply to cool down. The oxidative processes of the “minus” plates continue even after the charging is turned off.
In the future, you can try to apply the recovery process, but you should not expect a good result. Most often, the AGM battery has to be changed.
What Is Thermal Runaway And Why Should You Be Afraid Of It When Charging An AGM Battery
The term battery thermal runaway refers to the process that occurs during the charging process. Partially it is described above.
Its essence is that with an increase in the temperature indicators of the electrolytic liquid, the charging current also increases. If nothing is done, it can rise to the level of critical values.
During battery operation, electrolysis takes place with the release of H2 and O2. In normal mode, excess gases exit through the holes in the lids intended for this.
The result is the release of heat and heating of the electrolytic composition, a decrease in its resistance and an increase in the charge current.
The result is an even greater release rate of H2 and O2. In other words, the situation is aggravated and leads to an accident.
The likelihood of thermal runaway increases when the following factors are combined:
- Electrolyte deficiency in the battery.
- Natural wear of the active part of the electrodes.
- Increasing the charge voltage in relation to the nominal parameter.
- Rise in temperature in the engine compartment.
- Increased load on the battery during operation and more.
As a result of thermal runaway, the temperature of the battery rises sharply, which can lead to smoke and short circuits. In addition, the battery can simply explode due to the reaction of O2 and H2.
What Kind Of Charger Can Be Used For Charging
AGM batteries can be charged with a simple charger provided that their capacity is increased from 75 to 100 percent.
In the case of a deep discharge, it is necessary to use only automatic chargers with two modes for recovery: charge and buffer (storage).
It is important to buy devices with special controls that are suitable for AGM charging. In this case, preference should be given to devices with 3-stage charging.
Therefore, in the absence of experience, it is better to choose automatic analogues.
If we talk about specific models, it is worth highlighting the following:
- Maxpower LiFePO4 LFP12100 Battery.
- Vympel 57. Works on the principle of current reduction using the constant voltage method. The downside is that at the end of the charge, the current drops to the minimum parameter.
- Vympel 55 or 37.
- Pendant 912 is the best option for AGM batteries. The main thing is to understand the settings in order to prevent boiling of the electrolyte.
- Soyuz VS-1207A – also suitable in our case.
- Lavita Can be used for charging, but care must be taken when choosing the type of setting.
- Aurora Srinth 6 and others.
The choice is quite wide, but when buying, you need to clarify the possibility of charging an AGM battery with such a device and give preference to automatic pulse-type chargers.