Absorptive glass mats

The small pore size and the uniform distribution result in capillary forces which should allow wicking heights and thus battery heights of up to 30 cm. Due to the cavities required for gas transfer and under the effect of gravity, the electrolyte forms a filling profile, i.e., fewer cavities remain at the bottom than at the top. Therefore with absorptive glass mats a rather flat battery... 

Two VRLA battery technologies are currently predominant, i.e., absorptive glass mat (AGM) and gel designs. In the former, the AGM immobilizes the electrolyte and simultaneously functions as a separator. In gel batteries, the acid is immobilized by means of fumed silica, and an additional separator is required to fix the plate distance and to prevent electronic shorts. 

Absorptive glass mat (AGM) Very high porosity of separator High purity and stability of separator Low internal electrical resistance Relatively large separator pores acid stratification -electrolyte drainage risk of internal shorts -risk of thermal runaway -risk of PCL-3... 

The battery consists of two parallel strings of GNB Absolyte IIP, type 100A99 VRLA modules of the absorptive glass-mat (AGM) design. These are configured as... 

The original wooden sheet separators evolved through sintered PVC to polyethylene or polypropylene and, in some battery types, to absorptive glass mat (AGM). 

V. Naidenov, D. Pavlov, S. Ruevski, M. Chemeva, Three-layered absorptive glass mat separator for lead-acid batteries, Bui. Pat. 109755. 

Separators are used to electrically insulate between positive and negative plates to prevent a short circuit. Separators are porous to allow acid transport into or ont of the plates. The common separators are microporous polyethylene (PE) or absorptive glass mat (AGM). AGM is a nonwoven fabric made with glass microfiber. It is used widely for VRLAs because it is highly porous (90% to 95%) and can absorb more acid and has small pore size to maintain electrolyte levels in battery. Table 1.11 shows the properties of battery separator materials. 

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