TopTechnical DictionaryAGM (Absorbent Glass Mat) battery

AGM (Absorbent Glass Mat) battery

AGM (Absorbent Glass Mat) battery is a maintenance-free battery which, unlike a traditional lead-acid battery, has the electrolyte fully absorbed (bound) in special fibreglass mats.

 

The mats are also separators between the negative and positive plates. Due to the high porosity of the glass fibre mat's surface, the gas formed during charging is safely discharged into the negative electrode. There, in turn, it is converted into lead sulphate and water, i.e. recombination occurs.
This solution effectively protects the electrolyte from stratification and, in addition, reduces its loss to practically zero.

 

Examples of AGM batteries in the Delta-Opti shop offer

 

The main advantages of AGM batteries include:

 

  • increased efficiency of cyclic operation (possibility of multiple charging and discharging the battery without significant impact on its operational parameters),
  • increased resistance to deep discharge,
  • much lower specific resistance and therefore higher voltage attainable,
  • resistance to shocks, tilting, and the possibility of operating the battery in any position,
  • no possibility of electrolyte leakage even in the case of mechanical damage to the battery,
  • maintenance-free – no need to refill the electrolyte, and no need for checks of its state,
  • up to three times longer live compared to conventional battery,
  • reduced weight and dimensions compared to traditional battery of the same capacity.

     

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    Intended use:

     

    AGM batteries are suitable for both buffer operation (e.g. in alarm systems, UPS, emergency lighting) and cyclic operation (as the main power source for e.g. tools, toys, medical devices).
    If an AGM battery needs to be recharged, a suitable charger designed for this type of battery should be used. They have electronic current and voltage regulation, as well as temperature control. Despite the one-way valve in AGM batteries, which opens in the event of an excessive increase in pressure (e.g. due to overcharging), using normal chargers or rectifiers may damage the battery.
    Thanks to their ability to generate a high starting current, AGM batteries are also used in cars with start-stop systems due to their increased energy requirements, and in vehicles with energy recuperation during braking.

     

    Lifespan:

     

    Depending on the manufacturer, the battery model and how it is used, the life of the battery can reach over a dozen years. It is important to bear in mind factors that limit its service life, such as excessive charging current, repeated deep discharges or operation in temperature ranges significantly different from the rated temperature (for an AGM battery this is 20°C). Exceeding this value significantly affects its service life, which is halved for every 10°C increase in temperature from the rated value. This is why it is important to mount the battery away from heat sources such as transformers or heatsinks.
    In turn, low-temperature operation affects its rated capacity. At 0°C, for example, the battery loses around 20% of its capacity and at -30°C it already loses almost half.

     

    Very often AGM batteries are incorrectly referred to as gel batteries. Although both types of battery belong to the VRLA (Valve Regulated Lead Acid Battery) group, in which there is no access to the electrolyte, as the name suggests, the gel battery has an electrolyte in the form of a gel, which, unlike the AGM type of battery, is not contained solely in fibreglass separators but in the space between the electrodes.