The Difference Between AGM and Flooded Batteries

Posted by Crown Battery on May 1, 2020 1:11:22 PM

You most likely operate your vehicle, workplace equipment or renewable energy systems with rechargeable batteries. Rechargeable batteries account for nearly half of all worldwide battery sales. There are many different chemistries -- and to power anything that doesn’t fit in your hand or on your lap, the most popular and proven type of chemistry is the lead -acid battery.

Wet cell or “flooded” batteries and Absorbed Glass Mat (AGM) batteries are both lead batteries and are trusted to power billions of vehicles and hundreds of other applications . They contain an electrolyte solution which causes a chemical reaction and produces electrons. These batteries are recharged when put in contact with a reverse current.

There’s no perfect battery, but there is a right one for your application. Let’s take an objective look at pros and cons to consider.

Flooded/Wet Cell Batteries

Possibly the most “traditional” type of battery, wet (or “flooded”) batteries contain a combination of liquid electrolyte. The liquid in these batteries must be carefully measured and maintained in order for the battery to perform properly.

Pros: Wet Cell batteries are usually the best choice for backup power applications, utility, and grid energy storage.

    • Extended lifespan
    • 100+ years of improvements and proven field use
    • Highest ROI and lowest operating costs (50% - 90% less expensive than other chemistries
    • Easy maintenance


    • Requires periodic inspection and maintenance. 
    • Can be inadvertently damaged in forceful movement.
    • Extreme climates may have a greater effect on battery life due to evaporation or freezing.

While flooded batteries do require some maintenance, if taken care of properly this battery type will last longer than many of their counterparts.

Absorbed Glass Mat (AGM)

First used in military applications for extreme reliability and near-zero maintenance, AGM batteries offer several advantages.

AGM batteries can often be found in off-grid power systems including environmentally friendly renewable energy systems like wind and solar power. They are also great for electric vehicle service and uninterrupted power supply systems, as well as robotics and some ATVs and motorcycles.


    • Maintenance free
    • Long service life
    • High current delivery
    • Extremely low-maintenance: Does not require watering service, which lowers operating costs
    • Can perform better than flooded batteries in applications where maintenance is difficult to perform
    • Can be installed sideways -- electrolyte will remain inside


  • Take care when charging; over- and under charging can affect life and performance
  • Limit discharge to 50% of battery capacity for best reliability
  • Often higher up-front cost than lead-acid batteries (often 3X+ cheaper than lithium-ion, though)

What makes AGM batteries different?

They contain a special glass mat separator that wicks the electrolyte solution between the battery plates. This material’s design saturates the fiberglass with electrolyte – and stores the electrolyte in a “dry” or suspended state, rather than in free liquid form.

As the battery works, electrolyte is transferred from the glass mat to battery plates as required.  The mat contains enough electrolyte for the battery to deliver its full capacity and – should the battery case become damaged or the battery is tipped on its side – its electrolyte will not spill.


Have more questions about which battery is right for you?

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Tags: SLI Batteries, Battery Maintenance, Battery Cost