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AGM Batteries: Pros and Cons

As we learned in Types of Lead Acid Batteries, AGM (Absorbed Glass Mat) batteries, designed originally for the military, came into wide use in the 1980’s. Used in military aircraft, heavy duty vehicles and UPS, among other applications, they are lighter and more reliable, and able to withstand more punishing use.

In an AGM battery, the electrolyte is held next to the plates in thin fiberglass mats, instead of freely flooding the plates. This construction gives them some advantages over traditional, flooded, Sealed Lead Acid batteries.

Pros for AGM Batteries

  • They are spill proof. Because the acid is held in the fiberglass mats, they won’t spill, even if they are broken. They are safe to transport and are exempt from hazardous materials restrictions.
  • They are vibration resistant. They were designed to withstand the constant vibration of military airplanes and helicopters.
  • They are shock resistant.
  • They can withstand colder temperatures than a typical wet cell battery. If they are frozen, even though they won’t operate, they are not damaged.
  • They can be installed in any orientation.
  • They produce minimal gassing, so they can be used in less well ventilated areas.
  • They have a low self-discharge rate, meaning they can be stored for longer before they require a charge.
  • If well maintained, they last longer than SLA batteries.
  • They require no maintenance.

These dependable batteries are often used in marine vehicles, RVs, golf carts, wheelchairs and scooters, UPS systems and high end motorcycles where durability is required or battery orientation is an issue.

Cons for AGM Batteries

  • Manufacturing costs are higher, making the batteries more expensive.
  • They are sensitive to overcharging and high voltages, and require full charging between uses, which can make them un-suitable for some applications where returning them to a full charge is difficult.
  • They require a charger specifically for AGM batteries that monitors volts, amps and ambient temperatures.
  • Some older battery testers can’t accurately test AGM batteries.

AGM batteries are well designed, reliable, and durable power sources for applications where their advantages outweigh their disadvantages.