December 12 2019
f you're in a remote area and your home isn't connected to the utility grid, you're going to need more than a great solar system to keep everything powered at all times. This is where solar batteries come into play, and it's why having a reliable solar battery system is incredibly important. Being able to identify and separate the good batteries from the bad ones in the market can help you make a well-informed decision. Even if you are connected to the utility grid, having the right batteries that can save enough energy to have you covered when shortages in the grid occur can be a literal lifesaver.
However, batteries for solar system applications are much different than other types of batteries. Since the solar system batteries will be frequently discharged, they're designed to withstand constant recharging, and they're known in the battery world as deep-cycle batteries. The most popular types of deep-cycle batteries are flooded lead acid batteries, AGM batteries, Gel batteries and Lithium-Ion batteries.
These batteries were the most popular type used in solar system applications for a long time. They're very affordable and recyclable, and they can easily handle the daily charge cycling. Their safety and reliability is what made them popular for a lot of time, but they also have some drawbacks. For instance, flooded lead acid batteries produce a harmful byproduct in the form of gas, which is why proper ventilation is a must where they're located. Additionally, they're corrosive and bulky, and they require a fair amount of maintenance. The reason they're called flooded is that they're made of cells that feature plates that need to be kept underwater in order to function properly. You'll have to check and occasionally add water every few months to make sure they remain submerged.
AGM batteries are a type of lead acid batteries, but instead of being flooded, they are completely sealed. They feature a fiberglass matt which absorbs the electrolyte, and the plates are either flat or coiled into a spiral. The main advantage of AGM batteries is that they have a low internal resistance, therefore, they can endure higher temperatures, and they discharge slower than all other types of batteries. Unlike flooded lead acid batteries, the cells in AGM batteries are completely leak-proof, and they require no ventilation. Their low weight, resistance to cold temperature and long lifespan has quickly made them the favourite type of batteries for solar system applications.
Gel batteries are another type of sealed lead-acid batteries that specialise in deep-cycle applications. They use a fumed silicone to form the thickening agent for the electrolyte, which helps make it sturdier. That being said, these cells are very durable, require no maintenance, and feature high vibration- and shock-resistant properties. Further, Gel batteries operate well in cold and hot temperatures and have a long life-cycle. However, these batteries are ventless and they discharge faster than other types of batteries. The major disadvantage with these batteries is that they can be easily damaged if they're improperly charged.
Lithium-ion batteries are the battery technology, and while in the past they were mostly used for laptops and cellphones, their popularity is increasing in the renewable energy industry as well. Naturally, lithium-ion batteries are the most expensive type out of all other batteries, but they offer the longest lifespan, the highest efficiency, deeper discharges, no maintenance, and so on. The only disadvantage of these batteries is their high price cost.
Now that you have some basic understanding of the differences between the different types of batteries, here are some of the most frequently asked questions by first-time buyers.
All of the aforementioned types of batteries are great for use in solar systems, but as you can see - some more so than others. With that said, if you have the money to get lithium-ion batteries, by any means - go for them. Otherwise, you can get either Gel and AGM batteries. Whether you get Gel or AGM batteries will mainly depend on whether you have an understanding of how to properly charge the gel batteries and how to avoid overcharging them.
The amount of battery storage you need will depend on your energy usage, which is measured in kilowatt-hours per day. For instance, if the average monthly consumption by your household is around 600kWh, then the amount used in a day is around 20 kWh. Now, let's say that you'll only be using the power from the battery only throughout the evenings, which will come down to anywhere between 5-10kWh. This means that you'll need batteries with a total capacity of about 10kWh in capacity with a power rating of5 kW.
10kW solar systems are about the largest solar systems you can get for residential purposes. This system will use about forty 48V solar panels of 250W each, and will generate about 40kWh a day with only 8 hours of sun exposure. The total battery capacity needed to store all of this energy will be four 12V or two 24V batteries in series to make 48V, and 4 such banks in parallel to make 600Ah