Best Tractor Battery: Flooded Lead-Acid or AGM

Exploring the Pros and Cons Offered by Flooded Lead-Acid and AGM Batteries

by J. Keeler Johnson

The best tractor battery depends on several factors. Traditionally, flooded lead-acid batteries have been the go-to choice for starting engines and powering the other electrical needs of tractors, cars, trucks, and more. But another type of lead-acid battery—the absorbent glass-mat (AGM) battery—is an alternative offering both pros and cons.

What are the differences between flooded lead-acid and AGM batteries?

Lead-acid batteries surround lead plates with a mix of sulfuric acid and water called the electrolyte, generating a reaction that produces electricity. But the nuances of the design can vary.

In a flooded lead-acid battery, the electrolyte is in liquid form. In contrast, an AGM battery contains fiberglass mats that absorb the electrolyte and cushion the lead plates inside. An AGM battery is a type of valve-regulated lead-acid (VRLA) battery, also known as a sealed lead-acid battery.

Upsides of AGM batteries

AGM batteries offer many advantages compared to flooded lead-acid batteries:

  • The liquid electrolyte in a flooded lead-acid battery can leak out if the battery isn’t positioned upright. AGM batteries are sealed, so they can be mounted in any orientation without risk of leakage.
  • Flooded lead-acid batteries require regular maintenance, such as adding distilled water. AGM batteries do not.
  • The fiberglass mats make AGM batteries less susceptible to damage from vibrations than flooded lead-acid batteries.
  • AGM batteries perform well in a wide range of cold and hot temperatures.
  • AGM batteries charge faster and can have a longer lifespan than flooded lead-acid batteries.
  • When it comes to starting engines, a flooded lead-acid battery performs best when discharged only a little before recharging. AGM batteries can discharge deeper and still have enough oomph to start an engine, which frees up battery reserves for powering other electronics in a vehicle.
  • When charging, AGM batteries put out less gas (such as hydrogen, which can be explosive) than flooded lead-acid batteries.

Downsides of AGM batteries

If you’re thinking, “an AGM battery sounds awesome for my tractor,” that’s not surprising. But keep in mind there are downsides to AGM batteries:

  • AGM batteries are more expensive than flooded lead-acid batteries. While this can be offset by lower maintenance and longer lifespan, the increased up-front cost is worth keeping in mind.
  • AGM batteries can be damaged (and their lifespan thus shortened) by high voltages and overcharging. If you’re operating an older tractor, it’s possible its alternator isn’t suitable for recharging an AGM battery.
  • Along the same lines, if you’ll be charging your AGM battery with a standalone battery charger, you’ll need to get one that’s designed for charging AGM batteries.

Which makes the best tractor battery?

AGM batteries are commonly found in new cars because they’re excellent at powering the many electronics packed into modern automobiles while still offering enough power for starting the engine. Depending on the electrical requirements of your tractor, this may be less relevant; an old tractor might use the battery for starting the engine, powering headlights at night, and nothing more.

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A newer tractor, on the other hand, may have enough electronics on board to benefit from an AGM battery. And if you’re interested in any of the other benefits offered by AGM batteries (including the reduced maintenance requirements), you might want to splurge on the higher cost, provided your tractor can recharge an AGM battery without damaging it.

On that note, determining the best tractor battery for your needs may come down to the specifics of your tractor. If it’s a recent model compatible with AGM batteries, the upsides are yours to seize. But an older tractor might not reap as many benefits, and if you’re concerned about charging compatibility, sticking with a traditional flooded lead-acid battery might be best. If in doubt, consult a professional to determine the best tractor battery for your situation.

This article about the best tractor battery was written for Hobby Farms magazine online. Click here to subscribe.


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