The AGM is a newer type sealed lead-acid that uses absorbed glass mats between the plates. It is sealed, maintenance-free and the plates are rigidly mounted to withstand extensive shock and vibration. Nearly all AGM batteries are recombinant, meaning they can recombine 99% of the oxygen and hydrogen. There is almost no water is loss.
The charging voltages are the same as for other lead-acid batteries. Even under severe overcharge conditions, hydrogen emission is below the 4% specified for aircraft and enclosed spaces. The low self-discharge of 1-3% per month allows long storage before recharging. The AGM costs twice that of the flooded version of the same capacity. Because of durability, German high performance cars use AGM batteries in favor of the flooded type.
· Inexpensive and simple to manufacture.
· Mature, reliable and well-understood technology - when used correctly, lead-acid is durable and provides dependable service.
· The self-discharge is among the lowest of rechargeable battery systems.
· Capable of high discharge rates.
· Low energy density - poor weight-to-energy ratio limits use to stationary and wheeled applications.
· Cannot be stored in a discharged condition - the cell voltage should never drop below 2.10V.
· Allows only a limited number of full discharge cycles - well suited for standby applications that require only occasional deep discharges.
· lead content and electrolyte make the battery environmentally unfriendly.
· Transportation restrictions on flooded lead acid - there are environmental concerns regarding spillage.
· Thermal runaway can occur if improperly charged.