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  • Writer's pictureJustin Turner

AGM vs. Flooded Battery: Which is best for your rig?

It is my opinion that most vehicle owners give very little thought to the type of battery under their hood. Your vehicle (new or used) comes with one when you buy it, and you rarely think about it until it gives you warning signs of dying OR it dies and leaves you stranded somewhere. And by that time you are (typically) in a pinch to replace it so you drive to the nearest battery store and have them throw in a new one for the most affordable price possible. Can anyone else relate?

Batteries perform a number of important functions in your car, from providing the energy needed to start your engine, to powering electrical items when your vehicle is idle. The type of battery under your hood can have a pretty big impact on your car's performance. This article discusses the differences between flooded and AGM batteries, including the advantages and disadvantages of both.

Flooded Batteries

Standard flooded lead acid batteries are the most common batteries found in cars and trucks. They are cheaper than AGM batteries, making them the preferred choice for a large percentage of drivers.

The interior of 12-volt lead acid battery is divided into six different cells. In each cell, positive and negatively charged plates are stacked in an alternating pattern with a plastic separator placed between them. Each of the plates is then immersed in an electrolyte solution which creates a path for electricity to flow.

One thing to note, the flooded batteries used in your car are starting batteries, which are very different from those used in deep cycle operations. Starting batteries are designed to provide short, powerful bursts of power needed to turn over engines; they are not designed for the deep cycle operations required in a boat or to power additional conveniences in an RV.

AGM Batteries

AGM batteries (short for Absorbed Glass Mat) are constructed slightly differently than their flooded counterparts. The plate separator within an AGM battery is made of fiberglass, which helps to hold the electrolyte in place. This enables you to mount them in a variety of different positions (don't turn them upside down though) without fear of spilling, which can happen in flooded batteries. AGM batteries also have a lower internal resistance, giving them a higher voltage output and a dramatically shorter charging time.

AGM batteries also have a number of other advantages over flooded types:

- Longer life cycles

- Stand up much better to vibrations and impact

- More resistant to extreme temperatures, making them ideal for regions with high heat or intense cold.

*The greatest disadvantage of AGM batteries is price, with AGM batteries costing more than flooded batteries.

Back in 2018 I went into my garage to start up my Tacoma and head to work. There was a slight delay in the engine turning over (although it did start up), and I knew that the battery was likely ready to die. I headed straight to an Advance Auto Parts store and had them throw in a new battery. I had no idea (at the time) that I had purchased a Platinum AGM battery. I only realized it 3 years later when my battery was still going strong. I got exactly 4 years and 8 months out of that battery, which is far better than your standard lead acid...especially in AZ heat.

That experience turned me into an AGM convert. In April 2023 I replaced the Advance Auto battery in my Tacoma with a 24F X2 Power AGM battery from Batteries Plus, total cost of $380 with a 4 year warranty. My wife's Honda Odyssey also has an AGM (Interstate I believe), which we put in when the van wouldn't start during a gas stop in Yuma on our way to California in summer 2022. I anticipate I will get some good life out of my X2, and hopefully it'll die between year 3-4 so I can take advantage of the full warranty!

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