Solar Gel Batteries: Everything You Need to Know

Solar Gel Batteries: Everything You Need to Know

renogys blog Sep 8th 2021

If you’ve been looking into the various energy storage options that come with solar panels, you may have come across solar gel batteries. With so many decisions to make regarding  solar panels, it can be overwhelming by the time you get to the battery choices. That’s why you may be tempted to just choose what you’re familiar with, such as sealed lead-acid batteries or absorbent glass mat (AGM) batteries.

However, each of these battery types has its advantages and disadvantages, so it’s helpful to clearly understand each of your options before choosing one over the other. Whether you’re considering  home solar panel kits or RV solar panels, you’ll want to design the best solar system possible for your circumstances.

Let’s learn more about solar gel batteries and their competitors.  

What Is a Gel Battery?

Before we dive into the details, let’s take a moment to understand what deep-cycle gel batteries are and how they work.

A gel battery has the same design and functionality as a traditional lead-acid battery. The two batteries differ because solar gel batteries also contain silica in the electrolyte, which creates a gel-like substance. The gel electrolyte prevents the solar gel batteries from emitting as many fumes as the traditional battery. A gel battery is also easy to install in various positions because of its stability.  

All solar gel batteries are deep-cycle batteries, which are different from automotive batteries you see in vehicles, also known as starting, lighting, and ignition (SLI) batteries. Automotive batteries use very thin lead plates to produce a burst of energy. That surge helps the battery start your car quickly but would cause serious problems if hooked up to solar panels for home use.

On the other hand, deep-cycle batteries use thicker lead plates to create energy more evenly and slowly. They last longer than SLI batteries, and you can wire them together easily to create a battery bank. This feature makes deep-cycle batteries ideal for solar panel installations.  

solar gel battery

Advantages of Solar Gel Batteries

One of the advantages of solar gel batteries is they require little to no maintenance. Replacing the liquid in these batteries with gel means you don’t have to worry about leaks or other maintenance issues that could arise with lead-acid batteries.

Another benefit of deep-cycle gel batteries is how flexible you can be with where to install them. Not only can they be placed in any position without the fear of leaking or the need for maintenance access, but they are also resistant to heavy vibrations and other substantial impacts, making them ideal for tiny home solar energy systems.

Solar Gel Battery Disadvantages

While their reliability and versatility are significant pluses, solar gel batteries do come at a price, particularly a steeper price than standard wet cell batteries. Additionally, while deep-cycle gel batteries are resistant to burning out from a too deep discharge, they do require close monitoring while charging. Leaving solar gel batteries to charge even after they’ve reached capacity could cause voids with the electrolyte, something you cannot fix.  

Unfortunately, like all batteries, deep-cycle gel batteries can only withstand certain temperatures, so storing them in an area that gets too hot too frequently will shorten their lifespan.

Deep-cycle gel batteries are not the only option you have for DIY solar setups. Other deep-cycle options include lead-acid batteries and AGM batteries. Let’s learn more about how each deep-cycle battery operates and some of the differences between them.

Deep-Cycle Lead-Acid Batteries for Solar

There are two main types of lead-acid batteries available, flooded lead-acid batteries and sealed lead-acid batteries. Both batteries use the same basic chemical principles to produce electricity. Each battery has a positive lead dioxide plate (cathode), a negatively charged lead plate (anode), and a mixture of sulfuric acid and water called an electrolyte.  

When the plates are placed in the electrolyte mixture and connected to wires from a solar panel system, they can produce electricity. While both flooded and sealed deep-cycle batteries use lead plates and an electrolyte to produce a current, their designs differ significantly.

Flooded Lead-Acid Batteries

A flooded battery is the most basic design and, therefore, also the least expensive. Flooded lead-acid (FLA) batteries use rounded plates covered in electrolyte water mixed with acid. Because the plates need to be continually flooded (hence the name), these batteries require some regular maintenance. To keep up flooded lead-acid batteries, add distilled water once the battery’s evaporation levels are too high.  

To add distilled water, you must be able to open the plastic casing around the batteries. This design means the batteries need always to be standing upright and be in a well-ventilated area. Without proper ventilation, the hydrogen gas that emits every time the batteries discharge could build up to dangerous levels.

Without proper maintenance, these batteries will have fewer life cycles. However, when cared for properly, they can last anywhere from five to eight years for home energy use.

Sealed Lead-Acid Batteries

As their name implies, sealed lead-acid (SLA) batteries don’t require topping off the water regularly so that they can remain permanently sealed. Instead of replenishing the water supply, SLA batteries have one of two ways to contain their liquid.  

The first design is to include separators made from fiberglass between the positive and negative plates. The other design is to convert the liquid into a gel. With either method, the batteries will release hydrogen gas during discharges, so you’ll still need to keep them in a well-ventilated area, even if storing them on their sides is an option.

Absorbent Glass Mat (AGM) Batteries

When fiberglass is used to absorb the electrolyte and prevent it from leaking or evaporating, it’s called an absorbent glass mat (AGM) battery. The fiberglass acts sort of like a sponge and keeps the electrolyte close to the positive and negative plates. This allows AGM batteries to have a deep discharge while still providing the sulfate to mix back together with the hydrogen. This process is what lowers the amount of hydrogen gas released during discharges.

AGM batteries can discharge hundreds of times at up to 80% capacity and usually last around five years when used with a home energy system. While their low maintenance and easier storage make them appealing, they cost up to two times more than their counterparts as the design is more complex and requires more materials.

Learn more about What is an AGM Battery here. What is an AGM Battery

Gel Batteries

The other type of sealed lead-acid battery is a solar gel battery. AGM and gel batteries come with the same conveniences but operate differently. The silica gel in deep-cycle gel batteries suspends the sulfuric acid, giving the battery greater stability. It also has a lower rate of self-discharge over a long time.

constructure of solar gel battery

In addition, gel batteries release the least amount of hydrogen gas when they discharge, meaning ventilation isn’t as much of a priority. Solar gel batteries also function better at higher temperatures than their competitors, making them wise for warmer climates. However, the gel can run into issues in colder climates, something to keep in mind if you plan on storing your batteries in a basement or garage during wintertime.  

Because deep-cycle gel batteries can easily overcharge, you need to observe them rather closely to ensure a longer lifespan. It’s essential you connect these devices to the appropriate battery charger. A deep-cycle gel battery charger can monitor voltage and prevent it from going over the limit that solar gel batteries can handle. Without the proper gel cell battery charger, you may end up disappointed in your gel batteries’ performance.

AGM vs Gel Battery 

From the introduction of the two types of sealed lead-acid batteries above, you can notice that AGM and gel battery are quite distinct with each other in many ways. Here are the details offering you more ideas how to distinguish the two batteries.  

  • Working principle: the sealing principle of the two cells is the same. The difference lies in the way the electrolyte is "fixed" and the way that oxygen is supplied to the anode channel.
  • Interior structure: AGM batteries have an electrolyte (pure sulfuric acid) that is kept in suspension by the fiberglass, and come with thicker plates. Gel batteries use a gel electrolyte (made of sulfuric acid and silica gel) and thinner plates.
  • Discharge capacity: AGM batteries have a lower discharge capacity than today's gel-sealed batteries
  • Internal resistance: gel batteries have a higher internal resistance than AGM batteries.
  • Thermal runaway: gel batteries appear to be more adaptable to high temperatures, while AGM batteries can easily suffer from poor thermal conductivity.
  • Lifespan: there are many factors that affect the service life of VRLA batteries, both in terms of battery design and manufacture, and in terms of user usage and maintenance conditions.

Are 12V Gel Batteries Good for Solar?

A 12V 100AH gel battery does have possible applications for solar energy. However, not all solar setups will work well with deep-cycle gel batteries. Because of the amount of energy these batteries produce, along with their cost, 12V solar gel batteries work best with off-grid solar energy systems, such as  small solar panel kits designed for RVs, boats, tiny homes, vans, and small cabins.  

If you plan on utilizing solar power to provide energy to your entire home, deep-cycle gel batteries may not be the best investment. With more extensive solar setups, lithium-ion batteries are likely a better choice.

Are Lead-Acid Batteries Better than Lithium-Ion Batteries?

The answer to this question really depends on your need and situation, but generally speaking, no, lead-acid batteries are not better than lithium-ion batteries. Lithium-ion batteries are the latest in rechargeable storage technology for solar, electric, and other forms of energy. Because they use newer, more advanced technology, they create several advantages over their older competitors.  

For starters, lithium-ion batteries have a greater energy density, meaning they can store more energy using less space. Also, these batteries can be discharged regularly at up to 80% capacity without any downsides. Best of all, they have a greater tolerance for temperature fluctuations, making them more versatile and applicable to things like electric vehicles.

And to top it all off, lithium-ion batteries will last for at least ten years easily. Most lead-acid batteries will only last approximately seven years, and during that time, they won’t produce as many kilowatt-hours.

More information can be found in another article, " Are Lithium Batteries Worth the Investment?"

Which Is Cheaper?

When looking solely at pricing, you really need to break things down more extensively than just comparing price tags. To purchase and install lead-acid batteries for a complete home solar energy system, you can expect to pay around $7,500. However, the price will vary depending on the system's size and installation costs. It’s going to run closer to $12,000 on average to do the same with a top-of-the-line lithium-ion battery setup.

As long as it’s for storing solar energy from solar panels, both battery setups would qualify for the federal solar tax credit, saving you 26% in equipment and installation costs. That means that a lead-acid battery system could cost you closer to only $5,550, and a lithium-ion battery setup would be more like $8,800.

However, another factor you should consider when it comes to costs is each battery’s lifespan. If the average lead-acid battery setup lasts seven years, you’d be spending around $785 per year. Since lithium-ion batteries are reliable for at least ten years, that averages out to $880 per year, after the federal solar tax credit.  

In the end, you have to decide if the higher price tag of lithium-ion batteries is worth the conveniences and advantages you would gain compared to lead-acid batteries. As lithium-ion batteries grow in popularity, their price points will likely go down, making them a worthy long-term investment.

Deciding on Deep-Cycle Gel Batteries

Solar gel batteries can be an excellent option for certain solar energy system setups that don’t require powering an entire residence or building. These batteries operate much like other lead-acid batteries but come with a few extra advantages.

Deep-cycle gel batteries release less hydrogen gas during discharges. Because of their interior gel design, you can store them in various ways without the risk of leaks or malfunctions. They also cope better with being kept in higher temperatures but still have heat limitations.

For these reasons, 12V solar gel batteries are ideal for smaller solar panel setups, such as for a tiny home, RV, small cabin, or boat. Even though gel batteries can be wired into larger battery banks, the sheer number of gel batteries you would need for a standard residential solar setup makes them ineffective for such purposes. Instead, you may want to consider absorbent glass mat batteries or lithium-ion batteries for your home solar system.

Regardless of what setup you settle on, going solar is always going to be a wise investment. As renewable energy becomes more prevalent and necessary, solar energy systems (no matter how big or small) will create opportunities to have power when other alternatives run out or aren’t available.

Each year solar energy becomes more and more affordable, making the switch to solar an obvious choice. It may involve doing a bit of research and learning about the differences between gel batteries and lithium-ion batteries. Still, we’re confident it will be worth your time and energy.

Renogy gel battery

But if you want to avoid further hassle and select the right battery for your solar power system faster, Renogy offers you an all-in-one solution. Gel batteries, AGM batteries, lithium phosphorous batteries, and solar generators which also act as a role of power storage batteries, as well as other necessary components like battery chargers, are all available on the Renogy store.

Related articles:

What to Know About Lithium Batteries

Everything You Need to Know About Solar Energy & Solar Batteries

Solar battery charger guide

Expectations vs. Reality: Making Sense of Battery Voltage & Percentages