A Beginner's Guide to the Different Types of Batteries for Solar Systems

Renewable energy is a part of our green future and the number of homeowners installing solar powers is constantly increasing. And rightly so! Solar power is the perfect alternative to non-renewable energy, as it is sustainable and environmentally friendly.  

 However, after deciding to switch over to solar power, homeowners are faced with a new dilemma: are solar batteries needed? And what are these batteries used for exactly? Well, solar batteries are used for storing energy. To better understand why these batteries are used, let’s explain the different types of solar systems and how they work.   There are two main types of solar systems: grid-tied and off-grid. If a solar system is grid-tied, it means that if you need more power than your panels are producing, you can get power from the electric grid and will be charged by your electricity company. If, however, you are producing more power than you can consume, then the excess power goes into the power grid and your electricity company may compensate you for this. This will be reflected on your bill, however, the amount you will be compensated (if any) depends solely on your utility company. 

 An off-grid solar system can’t draw power from the grid. So, if you have consumed more power than you can produce, it is good to have a backup system such as a solar battery. When your panels produce extra electricity, it will be stored in the battery for later use. For those with an off-grid solar system, batteries are a must. The power will be generated during the day and then stored for use at night or at cloudy days.   Yet, we can say that solar batteries are also a good backup system for grid-tied solar systems. In case of a power outage in your area, you will be able to use the stored power in the batteries. And if your grid-tied solar system has a solar battery for storage, it means excess electricity will be sent to the grid only when your solar battery is full.  

So, depending on the type of solar system you have installed, a solar battery will either be necessary or an extra perk for your power supply. However, the batteries used for solar systems aren’t the same as regular batteries, also called starting or cranking batteries. A starting battery will provide you with a sudden and quick amount of energy, whereas a deep cycle battery will provide you with a steady amount of energy during a longer period of time. 

There are three main types of lead-acid deep cycle batteries: a flooded (wet cell), an absorbed glass matt (AGM) battery and a gel cell battery.  

Flooded (Wet Cell) Battery 

Deep cycle flooded batteries are the least expensive, however, they require the most maintenance. The reason they are called flooded is that they are kept underwater, so the water needs to be checked and maintained regularly in order to make sure that they are submerged. They also need to be well vented to releases the gases they produce and stored upright.  

 The main advantage of wet cell batteries is that they are affordable. And the main drawback is the maintenance required. If you don’t want to spend extra time monitoring your batteries, then sealed deep cycle batteries may be a better alternative for you.  

Absorbed Glass Matt (AGM) Battery  

Unlike flooded batteries, AGM batteries are sealed. They require no maintenance, as the batteries aren’t submerged. So, there is no need to check and maintain the water. The electrolytes are kept between absorbent glass, which is how the batteries got the name. The glass prevents leaking and evaporating, which means that these batteries don’t need to be vented. And seeing how they are leak-proof, absorbed glass matt batteries can be stored on their sides. Another advantage is that they are resistant to cold temperatures and don’t heat up easily.  AGM batteries are more expensive than flooded, even though they don’t last as long. However, as they require no maintenance, they can be stored in hard to reach places. They will also save you some time and effort.  

Gel Cell Battery 

A deep cycle gel battery, like the AGM, is a sealed lead-acid battery. Silica is used to make the electrolyte in a gel battery thicker. The main advantage of a quality deep cycle gel cell battery is that it has a low discharge, which means that it has a longer shelf life. These types of batteries also perform well in extreme weather – the electrolyte won’t evaporate when it is hot, nor will it freeze when it is too cold. Another similarity with AGM batteries is that gel batteries also don’t require water, so they are easier to maintain. The battery can be positioned sideways. Installing a gel deep cycle battery sideways is not recommended. The same applies for AGM batteries.   While AGM and gel batteries are mainly similar, both types having slower discharge rats, the main difference is that gel solar batteries are better for hot climates. In terms of upkeep, there isn’t much of a difference.