Flooded Batteries Versus AGM Batteries

Flooded Batteries Versus AGM Batteries

The purpose of this “Flooded Batteries VS AGM ” article is to help you understand the differences and similarities of the two battery types.

You are most likely using rechargeable batteries to operate one of the following: your vehicle, security alarm, industrial equipment or renewable energy systems. Rechargeable batteries come in many different types of chemistries. However, the most proven type and the most popular chemistry is the lead acid.

Wet battery cell are commonly referred to as “flooded” batteries. Absorbed Glass Mat batteries are referred to as AGM batteries. Both flooded and AGM batteries are considered lead batteries. These batteries contain an electrolyte solution which causes a chemical reaction that produces an electron flow. Lead acid batteries are recharged when they are put in contact with a reverse current. However, consider how they are designed, they each have their own pros and cons, which should be considered when selecting the batteries that are right for your application.

Flooded/Wet Cell Batteries

Flooded batteries are the most “traditional” type of battery. Flooded/wet cell batteries contain a combination of distilled water and an electrolyte, usually referred to as “acid”. Thie specific gravity of this liquid must be measured and maintained by a trained person on a regular basis.

Pros: Flooded/wet cell batteries are most suited for backup power applications, utility, and grid energy storage.

Cons: The most prominent disadvantage of flooded batteries is that they require regular inspection and maintenance. Flooded batteries will give of hydrogen gas when being charged. The hydrogen gas needs to be vented to the outside as it is explosive. Flooded batteries have on average a 5% self-discharge rate per month. I cold climates a flooded battery is at risk to freeze if too deeply discharged and consequently to become damaged and unusable.

Absorbed Glass Mat (AGM) Batteries

AGM (absorbed glass mat) batteries contain a specially designed glass mat separator, hence the name. The separator wicks the electrolyte solution between the battery plates. This design of this material allows the fiberglass to be saturated with electrolyte – and to store the electrolyte in a “dry” or suspended state, compared to the traditional free liquid form. The mat has sufficient electrolyte for the battery to deliver its full capacity.

Pros: AGM batteries are referred to as maintenance free batteries, since they do not require watering service. AGM batteries don’t have no free liquid and minimal gassing. As a result, AGM batteries can perform better than flooded/wet cell batteries in applications where regular maintenance is not possible. These batteries may be stored inside a dwelling as they do not give of hydrogen gas when being charged properly. AGM batteries are referred to as “non-spillable” or “spill-proof”. This means that if the battery is tipped on its side or if it becomes physically damaged, it will not loose its electrolyte. Another pro is the relatively low self-discharge rate of 2% per month. If the battery if properly charged going into the winter season it is likely not being damaged by cold temperatures.

Cons: AGM batteries are sensitive to undercharging, as doing so can significantly affect the life and performance of these batteries. AGM batteries perform most reliably they are only discharged to a maximum of 50% of their capacity. This is usually referred to as “depth of discharge” or “DOD”.