Solar storage batteries are the core of any home solar power or off-grid system. These batteries are used to store the energy generated by your solar panels during the day so that you can continue to use the power in the evening, through the night and on days where there is limited or no sunshine. Solar storage batteries can also be used as a backup system if you have intermittent or unreliable power supplied to your home. The battery industry is ever changing, but is it worth splashing out on the latest technology when you could be saving money by using slightly older ones? Let’s have a look at what the options are in 2019 and whether your should consider upgrading your batteries.
If you’re new to solar power or are just getting started with a new installation, you may want to have a look at this guide on switching to solar power. We also have a great guide on building your own solar panel from scratch if you’re feeling particularly hands-on.
Common Types of Batteries Available In 2019
Solar storage batteries may look similar to vehicle or truck batteries but they’re actually quite different, they’re designed for a deeper cycle (can be discharged further without damaging them), specifically to store energy for power backup and renewable energy systems. Here are some of the more common types of solar storage batteries available in 2019:
Lead Acid Batteries
Although one of the oldest technologies on this list, they’re still by far the most common and arguably the most affordable. Lead acid batteries are very similar in principle to general car batteries in that they have a number of “wet” cells linked together which are filled with acid. There are however some key differences in construction which enable them to be discharged more deeply (deep cycled) than regular car batteries.
These batteries are popular due to their low upfront cost and reliability. The main disadvantages of this type of battery are that they are generally quite heavy and bulky and they don’t last very long due to internal corrosion on the plates. They are also required to be stored in a ventilated area and you’ll need to check on their acid levels periodically and top them up when required.
AGM or absorbent glass mat batteries are simply a variation of the lead acid batteries discussed above in which the acid or electrolyte is absorbed by a glass mat, making them lighter and a bit more reliable, requiring less maintenance.
AGM batteries are particularly useful if you live in a cold region as they’re more resistant to cold temperatures than lead acid batteries and they do not require as much ventilation so they can be stored in a more confined space.
Gel batteries are again similar to lead acid batteries but the electrolyte is thickened to a gel-like state by an additive which makes the batteries less hazardous and less likely to leak. They require no ventilation and can be discharged at a higher rate than lead acid and AGM batteries.
They are a popular option for solar installations but they are very sensitive to being overcharged. Since most charging systems are designed by default for lead acid batteries, the lower charging voltage required by gel batteries results in them being easily destroyed.
One of the main benefits of gel batteries is the higher life-cycle (number of times the battery can be charged and discharged until it is no longer effective) than lead acid and AGM alternatives although they can sometimes be significantly more expensive.
One of the newer additions to the list, lithium-ion batteries are becoming an increasing popular option as their cost is steadily reducing. Lithium-ion batteries form the heart of most portable power tools, cellphones and portable electronics. They’re small and light weight for their power storage capacity, they can be discharged almost entirely without damaging them and they have a significantly higher life-cycle than the other batteries on this list. The Tesla Powerwall home energy storage solutions are powered with lithium-ion technology.
There are a number of different types of lithium-ion batteries available but the most common and most suitable type for solar installations is Lithium Iron Phosphate (LiFePO4).
The biggest disadvantage of lithium-ion batteries is the cost, they often cost four to six times what lead acid batteries of a similar capacity cost.
Some Things To Consider When Choosing Solar Batteries
There are a couple of things to consider when choosing which solar storage batteries to buy in order to get your best value for money and the type of battery which is most suitable for your application and needs:
- Battery Storage Capacity – your battery’s energy storage capacity generally means how much energy can be stored in the battery to be used at a later stage, obviously the more the better. Have a look at this article to figure out how much battery storage capacity you’ll need for your home.
- Cost – cost is probably going to be the main factor in deciding on the type and size of your storage batteries. Everyone’s needs and budgets are different so you’ll need to have a look at whether a high initial cost for potential future savings is your main goal or if you’d rather experiment on the cheaper side first and look at upgrading elements of your system in future.
- Battery Life & Warranty – battery life or the number of cycles the battery can go through before being considered to be ineffective is somewhat related to the cost. You’ll find that batteries which are initially cheaper tend to reach their cycle limit much faster than more expensive ones. Lead acid batteries can usually only do 500-1000 cycles depending on how deep the cycle is, while some modern lithium-ion batteries can do up to 5000 cycles. If you take into account that the lithium-ion batteries may last up to ten times longer than lead acid batteries then it may actually work out cheaper in the long run to go with lithium ion batteries. Also make sure that you know what the manufacturer’s warranty is so you know you’ll be covered if anything goes wrong with the battery prematurely.
- Charging Time – the speed at which your batteries charge can become important if you live in area with limited sunlight or you have a large storage capacity. Lithium-ion and gel batteries generally charge much faster (3-4 hours) than lead acid batteries which may take the whole day.
Our Top Battery Choices For 2019
- Lead Acid – Mighty Max 12V 100Ah Deep Cycle Lead Acid Battery. These lead acid batteries offer a great, sturdy design and at a really good price. They’re definitely not the best batteries on the market but you’ll struggle to find a more cost effective and reliable solution.
- AGM – ExpertPower 12V 33Ah Deep Cycle AGM Battery. This is one of the most trusted and reviewed batteries available on the market now and at $75, is still really affordable.
- Gel – NPP NPG12 150Ah Gel Deep Cycle Battery. We’ve chosen this gel battery for its reputation, capacity and price point. It is quite expensive at $310 but given its capacity of 150Ah, you’re actually paying less per Ah than the AGM battery listed above.
- Lithium-Ion – Renogy 12V 50Ah Lithium-Iron Phosphate Battery. This is by far the most expensive option on the list but for the size and lifespan you can expect from this battery, in our opinion it is worth it in the long run. You’ll be getting many years of reliable and consistent, maintenance free use from this battery.
We know that choosing the right battery for your solar power system might seem like a daunting task when you’re starting out but if you keep to your budget and consider your primary application, you can’t really go wrong. If you found this post helpful, please share it with your friends and let us know which battery option you’ve gone with in the comments section below. We’d love to hear from you!
Remember to consult a professional for advice or installation assistance if you are unsure of what you are doing, there batteries store a large amount of energy which can be dangerous if incorrectly installed.
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My name is Michael Klements and I started this blog in 2016 to share my DIY journey with you. I love fixing, renovating and building – I’m always looking for new projects and exciting DIY ideas. If you do too, grab a cup of coffee and settle in, I’m happy to have you here.