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A Complete Guide To Finding The Best Batteries For Solar

Updated: Mar 9, 2019



The biggest issue many people have with solar power is not harvesting but storing their solar energy. Fortunately, these days harnessing your power is as easy as installing a solar battery. But you should know that solar batteries can be pricey and often don’t come with the system so stick with us if you want to get the best batteries for solar power.


What Are Batteries For Solar?

A battery for solar panels stores power created by the solar system. Of course, there are various types of batteries, but their objective doesn't change. And if you truly want to avoid using the utility companies then you’ll need a way to both store and use the excess power you create during the day. This harnessed power can be used to sustain your home through the night until the sun comes back out in the morning.


Here’s a simple way of looking at it: you store food in the refrigerator, shoes in shoe boxes, water in water bottles, and energy in batteries. The problem with solar panel batteries is that they’re much more complicated to design and manufacture.


After all, this is a relatively new technology and it’s not your ordinary car battery. They're exposed to constant flows of high-voltage current so their stability and reliability must be impeccable. Therefor, it's important to choose a battery that fits your solar system in the most efficient way possible. If you use SunPower solar panels, then SunPower’s made batteries specifically designed to work with your panels.


Choosing The Optimal Battery For Solar

This section has one purpose: To help you find the best batteries for your solar panels. We'll talk about power, capacity, durability, longevity and other factors regarding these batteries.


On Capacity And Its Relation To Power Output

We measure batteries capacity in kilowatts per hour (kWh for future references.) Now, if you're buying batteries for your home solar system, it’s highly probable that this system supports stackable batteries.


If you don't already have a solar panel system, make sure you get one that supports these types of batteries (all modern systems support them).


When you’re designing your solar storage system, it’s always more efficient to include several batteries in it (to stack them). Including more cells means that you can store more power for a longer period. It also gives you a sense of security; should one or two batteries drop, others will provide you with enough time to replace those that are down.


Keep in mind that capacity only allows you to store energy and doesn't affect the way you can use this energy.


The current issue with solar batteries is that you may have to sacrifice power for capacity or vice versa. What this means is that you can opt for high-power output batteries, but they'll tend to have less storage capacity. Similarly, you can opt for high-capacity batteries with lower power output.


Generally speaking, batteries with high capacity will store large quantities of energy, but will also output very little of that energy into your home electrical system. Consequently, you'll be able to run several devices for an extended period, but may not be able to run all devices. On the contrary, batteries with a high power rating (measured in kW) will power your entire home, but for a shorter period.


The best advice is to talk to a professional who can help you determine exactly what you’ll need to power your home through the night without any problems. They'll be able to figure out how much power you use at various times of day/night. Then they can outfit your home with exactly what you need.


Understanding DoD

The therm DoD (Depth of Discharge[1]) can give you headaches. Here's a simple way of looking at it: the depth of discharge is the amount of energy a battery has already provided. If you have a battery that’s full (at 100%), we would say that it's DoD is 0%. If it’s at 70%, we would say that its DoD is 30%.


Why is DoD important? Batteries are self-contained units, which means that they need a minimal level of current to keep things going. They’re also limited by their nature (chemical structure), since they convert chemical energy into electricity (and some of that energy is lost in the conversion process.) Most manufacturers will choose to restrict battery's use with DoD to preserve its longevity. If you empty a battery from 100% to 0%, you are hurting its structure on a long-term basis.


Of course, this restriction isn't mandatory, merely suggestive. So, if you buy a battery with 90% DoD, this means that you shouldn't use more than 90% of its stored power (you can, but we advise not to). Consequently, it’s always better to buy batteries with high DoD if you want to buy those with the most efficiency and output potential.


Understanding Battery Efficiency

In the world of solar batteries, both storing and consuming requires some level of power. Let's say that you have a solar battery that has 10 kWh of electricity saved. When you start using this energy, some of that 10 kWh will be lost during conversion and transferring process [2].


If you get 9 kWh our of your battery (even though you stored 10 kWh), we would say that this battery is 90% efficient. Naturally, if you have a more efficient battery, you'll enjoy more energy output and better storage. We recommend going for notable battery manufacturers such as SunPower or even the LG Chem Battery.


Of course, the most efficient batteries are also the most expensive ones, but only on a short-term basis. As time goes by, the benefits of owning a high-efficiency battery will prevail and you'll be happy you chose a better battery. A solar battery is a long-term investment, which is why it's a good idea to buy something high end with better warranties.


Understanding Longevity And Efficiency

Batteries aren't indestructible, and they lose their quality over time (due to the way they function).


Over time, you'll notice that your batteries are storing and outputting less power, which, again, is natural. But how rapidly will they deteriorate? Manufacturers like SunPower and Enphase Energy usually measure the battery's longevity with what they call life cycle.


Basically, the cycle count determines the number of charge/drain times. If that number is 10,000, it means that you can charge/drain your battery 10,000 times.


Most manufacturers also give warranties on efficiency. They might say that your battery will have 10,000 cycles and that by the end of that cycle period, the battery will lose no more than 25% of its initial capacity.


Again, I suggest that you observe this from a business perspective; the more quality the investment, the better the long-term economic benefits and warranty are likely to be.


Types Of Batteries For Solar

Battery manufacturers have different ideas of what an ideal battery should be. For home use, you can choose between lithium ion, lead acid, and saltwater batteries. They differ not only in their chemical composition, but also in design, appeal, effects on the environment, efficiency, durability, resistance, and so forth. Below we’ll explain the difference...


Li-Ion Batteries

Lithium-ion batteries have been a go-to solution for many homeowners. Why? Because they're the best long-term investment and most people understand their solar panel system is also an investment. Consequently, they want to buy the best batteries available.


These batteries cost more than acid or saltwater batteries, but they also have more cycles. They’re also easier to maintain because they’re lightweight and free of lead and acids.


Lead Acid Batteries

Lead acid batteries for solar are the least expensive solution for your power storage needs. However, they have shorter lives and are often less efficient than lithium-ion or saltwater batteries. Moreover, they can be much harder to maintain.


For example, if you buy flooded acid batteries, you’ll have to refill them with acid on a regular basis. On the other hand, AGM batteries for solar feature more advanced design and require much less maintenance without the need for refilling or frequent monitoring.


Saltwater Batteries

The most significant advantage of saltwater batteries is their high DoD. These batteries are a novelty in the world of home solar energy storage, with a tendency to reduce hazardous effects that lithium-ion and lead-acid batteries can bring to the table.


Saltwater batteries [4] use water that contains salt (saline) as its electrolyte (hence the name saltwater). They’re also much safer due to their non-flammable design feature and they can be recycled when done.


The biggest problem with these batteries is that they’re very young technology. The company that initially produced them filed for bankruptcy back in 2017. Nevertheless, the company recouped and returned to the battery scene with a whole new look.


What Is The Best Battery For Your Needs?

Since we don't know what your needs are, we'll offer several solutions regarding specific situations. For instance, if you plan on going completely off the grid, then going for lithium-ion batteries with their massive power capacity and efficiency is the best option.


On the other hand, if you want to create a home energy storage just to have as a backup (or to use it occasionally), you can opt for lead-acid or saltwater batteries.


And if you’re like me, at the end of the day you want a battery that can power your house so you’ll invest in lithium-ion batteries. And if you need more power at any point, you can always add more batteries to your system for extra power, capacity and economic advantage.


Final Thoughts

Whether you want to invest in your home or business, installing solar panels can save you thousands of dollars on power bills. Moreover, you won't need to depend on anyone but the power of the sun when it comes to electricity production.


If you have SunPower Solar Panels, then buying a SunPower battery that’s perfectly crafted to work with your system is definitely the way to go. It's one of the best batteries for solar and comes with an outstanding warranty.


If you have any questions about solar batteries, let us know in the comment section below.


References

1 - https://www.youtube.com/watch?v=sM2ss-EvAco

2 - https://www.youtube.com/watch?v=-I87Qg24tMk

3 - https://www.youtube.com/watch?v=9OVtk6G2TnQ

4 - https://en.wikipedia.org/wiki/Salt_water_battery