Absorbent glass mat (AGM) is a class of VRLA battery in which the electrolyte is absorbed into a mat of fine glass fibers. The plates in an AGM battery may be flat like a wet cell lead-acid battery in a rectangular case. In cylindrical AGMs, the plates are thin and wound, like most consumer disposable and rechargeable cells, into spirals so they are also sometimes referred to as spiral wound. Their unique (for lead-acid chemistries) construction also allows for the lead in their plates to be purer as they no longer need to support their own weight as in traditional cells. Their internal resistance is lower than traditional cells due to plate proximity and the pure lead plates have lower resistivity, they handle higher temperatures better, and self-discharge more slowly.
These batteries are often referred to as sealed lead-acid (SLA) batteries due to their non-leaking containers.
Their specific power is very good and they can be charged and discharged quite rapidly. They are often used in high performance electric vehicles due to their high power density. An AGM battery is a lead-acid electric storage battery that:
- is sealed using special pressure valves and should
never be opened.
- is completely maintenance-free.*
- has all of its electrolyte absorbed in separators consisting
of a sponge-like mass of matted glass fibers.
- uses a recombination reaction to prevent the escape of
hydrogen and oxygen gases normally lost in a flooded
lead-acid battery (particularly in deep cycle applications).
- is non-spillable, and therefore can be operated in virtually
any position. However, upside-down installation is not
*Connections must be retorqued and the batteries should be cleaned periodically.