CLOSED TYP BATTERIES AGM - GEL - LEAD - ACID

In order to achieve a lead-acid battery maintenance-free, a closed-loop battery was created in the 1970s by adding a valve to control the venting of gases during charging and discharging operation. The purpose of the valve is to act as a safety vent when gases are generated during overload or discharge. The lead-acid cell-type battery facilitates the combination of hydrogen and oxygen during the charging process and the creation of water, which prevents the battery from drying out. It is a regulated lead-acid battery with a non-opening valve for adding acid. Sealed batteries are also called sealed lead-acid (SLA) electrolytic batteries. These batteries form a stable electrolyte that has fewer electrolytes than open-type liquid cell batteries. As these batteries are sealed - closed and sealed in liquid, they can be installed and operated in any position, even sideways or vertically. These batteries are used in cases where hydrogen gasification is not tolerated or the battery needs to be moved during transport. There are two types of closed battery for photovoltaics: GEL batteries electrolyte gel and AGM batteries.

Closed type battery: GEL deep discharge battery

Η gel battery (closed type) uses a mixture of silicon oxide and sulfuric acid (electrolyte) to immobilize the electrolyte. This mixture, when added to the battery as a hot liquid, turns into a gel as it cools.

After some time, the gel dries gradually creating small cracks and gaps that create pathways for gas movement and reconstruction. These gases, hydrogen and oxygen, produced as a result of a chemical reaction on the positive and negative plates, combine to form water. This process eliminates the need to add water. However, excess gases escape through the pressure openings. This results in the gel drying and shrinking, causing it to lose contact with the plates and reduce capacity. This type of lead-acid closed type batteries are suitable for stand-alone photovoltaic installations and autonomous photovoltaic systems in remote areas due to less maintenance, easy transport and no use of liquid electrolyte. Closed gel batteries, although less hazardous and easy to maintain, can only be used in limited conditions due to limited starting currents.

Closed type battery: Glass absorption electrolyte battery - AGM battery

The electrolyte (sulfuric acid) in this cell is immobilized using a thin absorbent mesh of fiberglass (fiberglass) between the lead plates. The glass wool layer with small pores absorbs the electrolytic acid and immobilizes it while retaining the available acid in the plates. The fiberglass layer also acts as a divider between the slabs. Its construction allows hydrogen and oxygen to move and recombine to create water. Its charging rate AGM battery is five times faster than hers open type battery. The closed cycle life of a closed-loop battery is better than that of an open-type battery. The cost of AGM is greater than open type battery, but is less than the cost of the gel battery. The AGM works well as a medium-sized battery with a capacity of 50Ah to 280Ah. Its limitations include sensitivity to overload, gradual decline and low specific energy. AGM is less environmentally friendly compared to the open battery. It is sensitive to overload and must be stored in a charged state.