Operating principle

The AGM battery differs from conventional batteries in its non-polluting and substance-retaining behavior during charging.

When a battery is charged, the electrolysis process emits the gases oxygen and hydrogen.

• In a conventional wet lead calcium battery, the two gases hydrogen and oxygen are dissipated into the atmosphere.
• In an AGM battery, the two gases are converted back into water: The oxygen which is created at the positive electrode during charging passes through the permeable glass fibre fleece to the negative electrode. At the negative electrode the oxygen reacts with the arriving hydrogen ions in the electrolyte to form water (oxygen cycle).

In this manner, the gas, and thus the electrolyte, is not lost.

Only in the event of an excessively heavy build-up of gas, i.e. excessively high pressure build-up (20 to 200 mbar), does the pressure relief valve discharge the gas. In this process, the pressure relief valve does not allow any oxygen in the air to enter. Because the pressure in the battery is regulated by a valve, the AGM battery is also known as the VRLA battery (valve-regulated lead acid).