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Gel vs AGM: Not Quite the Battle of the Ages, But Nice to Know

What is the difference between gel cell and AGM batteries?

AGM Vs Gel Batteries Tutorial

AGM and Gel cell batteries are both non-spillable and maintenance-free batteries that share quite a few common traits. Because of these common traits, they often get mistaken for each other, which can cause issues if the battery is being used in an application that is not ideal for its technology.

In this article, we plan on covering the following:

  1. Construction Differences
  2. Common Traits
  3. AGM Characteristics
  4. AGM Charging
  5. AGM Advantages
  6. Gel Characteristics
  7. Gel Charging
  8. Gel Advantages

Construction Differences

AGM Construction

AGM stands for absorbed glass mat, which uses a specially designed glass mat to absorb the battery’s liquid electrolyte surrounding the lead plates. AGM batteries contain enough liquid to keep the matting wet but not too much liquid where excess liquid is not absorbed.

For this reason, AGM batteries are considered non-spillable batteries, and should the case break, no free liquid is available to leak out.

Gel Construction

Gel Cell batteries contain an acid-based silica-type gel electrolyte. This electrolyte has the consistency of a thick paste-like material that allows electrons to flow between plates.

Gel batteries like AGMs are considered non-spillable and will not leak from the battery if the case is broken.

Common Traits

Often, AGM Batteries are mistakenly identified as Gel Cell Batteries, given their non-spillable construction. Both AGM and Gel batteries have similar traits, such as being:

  • Non-spillable
  • Found in Deep cycle applications
  • Mounted on their side or standing up
  • Low self-discharge rate
  • Safe for use in limited ventilation areas
  • May be transported via Air or Ground safely without special handling

AGM Characteristics

AGMs are versatile batteries that tend to outsell Gel batteries by at least 100 to 1. The main reason for their versatility is that they can release high bursts of amps and hold under load at lower depths of discharge.

An AGM's ability to release high bursts of amps makes them ideal for starting applications. Today, you will find starting AGM batteries in Automotive, Marine, RV, Motorcycle, ATV, and other Powersport applications. In fact, most motorcycle and ATV manufacturers primarily use AGM batteries for their OEM batteries.

While AGM batteries use a liquid electrolyte, they do not off-gas like flooded batteries. AGMs are designed to reintroduce the gasses back into the battery, so they are great for applications with limited ventilation. Also, since the batteries do not off-gas, corrosion is non-existent.

An AGM's ability to hold under load at lower depths of discharge gives it an added edge over flooded or gel batteries. Just be aware that AGM batteries typically have the same cycle life as flooded batteries, so excessively discharging the battery can reduce cycle life.

The average AGM brand will see about 500 cycles at 50% depth of discharge, with premium brands like Lifeline Battery seeing 1000+ cycles. If your needs are not extreme, it is worth suitably sizing the battery so it isn’t discharged over 50%.

Charging an AGM Battery

Picture of an Quick Power battery isolator

Since AGM batteries use liquid electrolyte, they can typically be charged with the same charger you used on your flooded batteries. In most cases, a good-quality standard battery charger or engine alternator using a battery isolator is all you will need for an AGM battery.

The only issue you might need to address regarding charging is that more advanced charges might have an equalization setting. Since the electrolyte in an AGM battery is suspended in the fiberglass matting, there is no reason to equalize the battery so that this setting can be disabled.

If you have a newer charger with an AGM setting, we recommend using this setting, as it will typically disable the charger's equalization setting.

AGM Advantages

While not a complete list, these are the main advantages of AGM batteries:

  • Low self-discharge rate
  • Ability to hold under load at lower depths of discharge.
  • Ability to release high bursts of amp.
  • Used in both Starting and Deep Cycle Applications
  • No need for a special charger means they can easily replace a flooded battery.
  • Non-spillable
  • No corrosion

Gel Characteristics

Due to their construction, Gel Cell Batteries are typically a bit more costly. However, gel batteries excel in cycle life, with some higher-end lines like MK Battery offering up to 2x the cycle life at a 50% depth of discharge over the average AGM battery.

Gel batteries react slower than AGM or Flooded batteries. This slower reaction time has the positive effect of increasing cycle life and slowing the battery's aging process.

For this reason, we find them being used exclusively by mobility devices like electric wheelchairs and scooters. We also find gel batteries great for marine and RV applications, where the batteries tend to get excessively discharged.

GEL Limitations

Gel cell batteries, however, do have a couple of caveats that people need to be aware of when deciding whether to go with an AGM or Gel battery.

First, gel batteries are typically only recommended for moderate deep-cycle applications as they cannot release high amounts of amps like an AGM or flooded battery. In other words, we would not recommend a gel battery for an application like a winch that requires a 100+ amp draw.

Second, due to their slower reaction time, the same group-size battery tends to be lower in capacity than an AGM or Flooded Battery. For instance, MK’s group 27 AGM battery is rated at 92 AH, whereas the MK group 27 gel battery is rated at 88 AH. This slight reduction is usually an insignificant loss, but it is something that you should keep in mind if your needs are extreme.

Charging A Gel Battery

Lastly, most gel batteries require a gel-specific charger since they charge a few tenths of a volt lower than most AGM or flooded batteries. If you're leaning towards a gel battery, pay special attention to the charging range your gel battery accepts.

In some cases, you may need to upgrade your charger to a gel-specific charger. Otherwise, using the incorrect charger can result in premature failure. If you need help selecting a proper charger for your gel battery, contact our tech department.

Gel Advantages

Besides the common traits above, the following are some of the more significant gel battery advantages:

  • Ages slower in warm weather
  • Freeze resistant
  • Very low self-discharge rate
  • Higher cycle life
  • Tolerates excessive discharge better than a flooded or AGM.

If you are unsure which battery or charger is best for your application, please call or email our tech people for help making the correct selection

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