What’s the best type of battery?

Understanding the basic differences between the three main battery types – Flooded Lead Acid (FLA), Absorbed Glass Mat (AGM) and Gel Cell – will help to determine the best battery for your trucks and equipment

“These three main types of equipment and vehicle batteries are all lead-acid batteries with different construction, different performance characteristics and different charging requirements,” says Gale Kimbrough, manager of the battery engineering and testing lab at Interstate Batteries.

All lead-acid batteries feature lead plates surrounded by an electrolyte containing sulfuric acid. During charging, the positive and negative plates react so that positively charged electrons travel to the negative and negatively charged electrons travel to the positive, using electrolyte as a bridge. The batteries are discharged during use by reversing that process.

If the battery is permanently sealed – that is, its caps can’t be removed – and is labeled as AGM or Gel, it’s known as a valve-regulated lead-acid battery. These batteries come equipped with one-way pressure release vents.

“Batteries have evolved a great deal,” says Kimbrough. “For example, lead plates have been married to different alloys. One of the latest changes has been the use of lead alloyed with calcium, which minimizes the creation of hydrogen and oxygen gases during normal charging.”

The three main battery types are distinguishable by design and primary function.

Flooded Lead Acid

“FLAs are the oldest battery design and have been part of road vehicles since cars gave up hand cranks,” says Kimbrough.

The FLA offers a versatile design. Depending on construction, FLAs can produce high cold cranking amp (CCA) power availability (shallow cycling) and/or a combination of cranking and deep cycling, or deep cycling only.

FLAs may be permanently sealed or designed with accessible vent caps.

Charging options for FLA batteries are probably the widest, ranging from the vehicle recharging system to most non-vehicle rechargers.

Gel Cell

Gel Cell batteries feature a design in which silica has been added to the battery during manufacturing to congeal liquid electrolyte.

“They were developed more than 30 years ago to satisfy a need for a deep cycle battery that was sealed because they could be used in enclosed applications,” says Kimbrough. “They were originally used in the telephone industry as backup power for equipment.”

Gel Cell batteries usually offer a higher reserve capacity than other batteries.

“They can be used for starting if required, but typically don’t produce the same cold cranking amps as an FLA or an AGM battery,” says Kimbrough. “They can be made to deep cycle, but these batteries are traditionally used as backup power or for lighting.”

Gel Cell batteries must be recharged using lower voltage than other lead-acid batteries.

Absorbed Glass Mat

What makes the AGM different is a sponge-like fiberglass material separating negative and positive plates. This micro-glass material absorbs the electrolyte solution and keeps it immobilized while maintaining contact with the plates.

The batteries were introduced in the mid-1980s for use in military aircraft because they eliminated the risk of formation of explosive gases. More expensive than FLAs, AGM batteries are gradually replacing Gel Cells, with which they’re often confused.

“The strength of the design is that the glass mat and electrolyte combination offer a very low resistance,” says Kimbrough.

AGM batteries can be used in high cranking and/or deep cycling applications, such as vehicle starting or electric vehicles, depending on their designed purpose.

“Recent AGM pure lead technology uses thinner plates made of 99.99 percent pure virgin lead,” notes Kimbrough. “This technology has allowed AGMs to perform with deep cycling and cranking combined.”

Which battery to choose?

Choosing the right battery for your trucks and equipment is usually a matter of balancing cost and performance. If an FLA isn’t providing the performance required, it may be time to upgrade to a heavy-duty FLA or an AGM.

“If your regular FLA is performing for one year or less, you need to investigate an upgrade to either a heavier duty FLA or AGM,” says Kimbrough. “Also make sure that the batteries you’re using or buying haven’t aged on the shelf. Excessive storage can cut into performance life.“

AGM batteries also perform better than FLAs under heavy vibration, the type of conditions you experience with mini-excavation equipment, for instance. “They typically offer two to five times additional vibration resistance than flooded unless the flooded battery meets extra heavy-duty requirements,” Kimbrough notes.

If equipment is stored for extended periods of time between uses, AGMs hold their charge longer than FLAs.

Maintenance matters

Kimbrough recommends that all batteries be visually inspected every three to six months. Terminals should be inspected for corrosion and inspected for cleanliness, since dirt can discharge electricity across positive and negative terminals.

While some FLA batteries have vent caps that can open, others are sealed. If the caps are accessible, the battery can be visually inspected to see if electrolyte continues to cover the plates as specified by the manufacturer.

“If levels are low, you can add water, preferably deionized or distilled, to top up the fluid,” says Kimbrough. “You’ll probably need to do this more often in high heat or extreme cold conditions.”

Depending on their use, batteries can perform for longer or shorter times than their expected lifespan. One testing method involves checking the battery’s voltage at rest to help determine its state of charge.

“A generic 12-volt battery that tests at 12.00 volts can indicate an approximate 20 percent remaining charge level,” says Kimbrough. “Although it varies depending on the type of battery, typically 12.75 volts to 12.95 volts indicates a near-full charge in a battery at rest.”