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If you’re looking for maximum efficiency, a smaller footprint, low maintenance, and longer shelf life, you can go ahead and disregard the entire lead-acid solar battery market — What you need is a lithium (LiFePO4) solar battery!
LiFePO4 batteries are generally considered the best of the best when it comes to solar energy storage, so despite the larger price tags, many enthusiasts decide to skip lead-acid and start their solar journey with lithium.
But with so many options out there, it can be headache-inducing trying to figure out which is best, so let’s break it down with this comprehensive lithium solar battery buyer’s guide!
Is There Such A Thing As “The Best” Lithium Solar Battery?
Okay, so I’d just like to preface this guide by saying there is no one “best” lithium solar battery. Almost all lithium batteries on the market are well suited to a specific, user-defined solar goal.
Unfortunately, this means I can’t immediately direct you to the perfect solar battery, but on the plus side, it forces you to consider what your solar goals are, ensuring the constituent parts of your system share a synergy that leans towards this solar mission statement of yours.
And with that said, we can dive into the guide!
Lithium Solar Battery Buyer’s Guide
Establishing Your Solar Mission
Continuing on from my last point, your first port of call should be to establish what you want to achieve with your solar energy system.
Once your goals are defined, you know how to use the proceeding considerations to find the perfect lithium solar battery for you.
Here are some common mission statements to get the creative juices flowing:
- I’m hoping to go completely off-grid and power my entire home with solar power.
- I need to power my long-weekend camping trips.
- I want to power a specific or group of appliances
- I want to power my RV using predominantly solar power.
- I want a solar energy system I can control remotely using an app.
Battery Capacity Amp Hours And kWh
Now you need to know how battery power/capacity is defined.
A manufacturer may give the watt hour rating and amperage to communicate power, but when figuring out how much power you’re going to need, it’s best to work in kilowatt hours (kWh).
Thankfully, as long as you have the amp hours and the voltage of the battery in question, you can figure out kWh with this simple equation:
kWh = Ah x V ÷ 1000
So, for example, let’s say a 12 V solar battery was rated for 200 Ah, we would do the following sum:
200 (Ah) x 12 (V) = 2400… 2400 ÷ 1000 = 2.4 kWh
Calculating Your Load
It’s no use knowing how to read the capacity of a lithium solar battery if you don’t actually know specifically how much power you’re going to need to complete your mission statement.
This is why the next step is assessing the power consumption of every electrical item or process pertaining to your solar goal.
You’ll also want to consider a timeframe, i.e. how many kWh do all your electric items consume in a day, week, or month?
Once you’ve got that figured out, you just need to match the hypothetical kWh load with a battery (or batteries) that can store that much energy.
The Question Of Climate
No matter your solar goal, if you’re in an area that commonly has a gloomy climate, your solar panels aren’t going to be pulling in much power, which means you’ll need to build up a hefty backlog of power to stay juiced on solar alone.
This means you’ll need a larger battery or power bank.
Let’s say you lived in Massachusetts that famously gets long, cold winters, and you wanted a solar backup that could supply power to your home for an entire week with little to no sun.
You’d need a lot more storage capacity than someone living in, say, Arizona, a state that gets lots of sun.
That said, your panels are going to be much busier in Arizona, so you’ll need a relatively robust power bank just to make use of the available energy.
Where Does Voltage Come In?
If we picture electricity as water in a hose, voltage would be the water pressure. It decides which way the electricity flows.
Now, being that we want electricity to travel from our solar panels to our battery, the voltage of the solar panels needs to exceed that of the battery.
If it doesn’t, then the power won’t flow efficiently, as the battery’s voltage will be holding it back.
The golden rule is to pair a battery with a solar panel(s) that have 20 to 30% higher voltage than the battery.
So, for a 12 V battery, you’d need a 14.4 V panel system, and for a 48 V battery, you’d need a 21.6 V system.
Single Or Multiple Batteries?
Whether you pick up a single or a few lithium solar batteries depends entirely on the combined load you need to support.
While Tesla produces the mammoth Powerwall solar battery that boasts a 13.5 kWh capacity, it’s a mighty expensive unit, and you generally won’t find that sort of power across the general market.
You’re more likely going to run into 200–400 Ah/2–5 kWh batteries. This Ampere Time LiFePO4 battery is a pretty standard example of what's available at a reasonable price. At 12 V and 200 Ah, it amounts to 2.4 kWh.
If you’re willing to spend a bit more, you can snag something like this 12.8V, 400 Ah beast from Lossigy, but that still only works out as 5.12 kWh, way behind the trailblazing Tesla Powerwall.
In light of this, if you’ve got a mammoth load to support, you’ll likely need to buy multiple lithium solar batteries and combine them into a super solar power bank.
Shelf & And Cycle Life
All rechargeable batteries suffer from two forms of expiration, shelf life and cycle life.
Shelf life refers to the prime use duration, and cycle life refers to how many times you can discharge and recharge it before it kicks the bucket.
In other words, shelf life marks the point at which the battery is liable to die of old age, while cycle life establishes when the battery is likely to be worked to death, if you will.
Typically, lithium solar batteries last for 10 years and beyond, with a cycle life that often exceeds 2000 charges from max DoD, but this isn’t a given.
You should always check both the perishable aspects of a battery before buying.
Depth Of Discharge (DoD)
DoD indicates how much you can safely discharge a battery. Exceeding this rate of discharge can harm the battery and reduce its cycle life.
Oftentimes, the cycle life of a battery will be given alongside a DoD rate.
For instance, this EcoWorthy LiFePO4 battery can be cycled 3000 times from a DoD of 99%. DoD can be a lot lower than this, sometimes even around 80%, so it always pays to check before purchasing a battery.
Ideally, you should look for a battery with a warranty of 10 years, as that’s the minimum shelf life of a lithium unit, but you may get stuck with just a 5-year warranty, which isn’t bad. Avoid anything less than that though.
Congratulations — You’re now closer than ever to finding the perfect lithium solar battery for your green power setup.
Remember to come up with your solar mission statement before you begin your search, then use the points discussed above to zone in on the sort of battery that suits your needs.