Estimated reading time: 8 minutes
Are you researching batteries for living off the grid? If so, you know there’s a lot of information available online.
Yet most of it assumes the reader has some knowledge of batteries. If you don’t, here’s a quick overview of battery bank basics for an off-grid home.
What is a Battery Bank?
In simple terms, a battery bank is just a place to store energy that you've acquired through the use of generators, solar power, wind power, or even aqua power. Our battery bank plays an important role as part of our off grid home system.
For clarity, aqua power is not “Aquaman”. It is energy generated through the use of a water turbine, a topic for a different article.
A battery bank is an appropriate term since it's like banking. You literally save “energy” for a rainy day. The next question to consider is: “Do I really need a battery bank?”
The answer, of course, is not so simple and we will rely on a tried and true lawyer's response: it depends.
Batteries for Living Off The Grid: Why a Battery Bank is Best
The real advantage with a battery bank occurs when you’re off the grid and want to have power available on cloudy days, nighttime, etc. Yet you don't want to run a generator 24/7.
The larger the battery bank, the more power you can store. This allows you to run longer without the need to replenish your power. And this is an important consideration when it comes to batteries for living off the grid.
The dilemma you face is that very few areas have a consistent balance of sunshine/nightfall/clear skies/cloudy skies/comfortable temperature day after day, month after month, and year after year. If they did, it would be easier to establish a system that has a good balance of available power.
Related: Generators for Beginners
Planning an Off-Grid Battery System
To begin with, there are different types of batteries, voltages, amperage, and costs to consider when planning your system. Since batteries aren't cheap, the ideal situation is to find a balance between your average usage and what type of energy source you have.
For example, if you have access to hydro through a local utility company, their energy is usually less expensive than any power you can generate. So if your sole interest is from a financial perspective, it is prudent to consider keeping that power source.
Best Batteries for Living Off The Grid
In the lead-acid category, there are generally three types of batteries: flooded, absorbent glass mat (AGM), and gel batteries.
Flooded batteries are maintainable and have to be checked fairly regularly to ensure the water levels are correct and the plates remain submerged.
The other two options are absorbent glass mat (AGM) and gel batteries. They require less maintenance. These are generally more expensive to buy initially than flooded lead-acid batteries, but what you save in both maintenance time and cost is a consideration for some people.
Lithium batteries are also on the market now, which some are considering for off-grid applications. They are the most expensive to purchase. However, they have more cycles and more amp capacity delivered over the life of the battery.
Battery Bank Setup Basics
When setting up your battery bank there are several things to think about. One of them is the input voltage. This is generally defined by the input voltage of the inverter, which changes the DC current into AC current.
Usually, that will be 12, 24, or 48 volts with higher voltage, generally meaning that less amperage input is required.
The easy way to look at this is that if you only require power for things such as general lighting, small electrical appliances, and any appliances that don't generate heat, 12-volt is usually sufficient for off grid electricity storage.
If you're planning to run heat-generating appliances, electric stove, pumps, microwave, iron, hairdryer, etc. a 24-volt system is a better setup. If you're running any commercial equipment such as electric planers, welders, sawmills, etc. a 48-volt system might be the better way to go.
Having said all this, your average household can generally operate quite comfortably on a 24-volt setup. Any occasional heavier equipment can get powered directly from a generator.
Batteries come in many configurations, usually in sets of 2, 4, 6, 8, and 12 volts. The key point here is that regardless of the grouping, batteries run in series. Each group must equal either 12, 24, or 48 volts while using the same voltage battery.
Examples of Battery Bank Configurations
For simplicity I will include some examples knowing each number represents volts:
2+2+2+2+2+2=12 or 2+2+2+2+2+2+2+2+2+2+2+2=24 and so on
6+6=12 or 6+6+6+6=24 and so on
12=12 or 12+12=24 or 12+12+12+12=48
Now the above groupings are called “batteries running in series” to give you either 12, 24, or 48 volt systems. You can easily increase your system's amperage (storage) by running similar series (groups) of batteries in parallel.
This means, for example, a 24-volt system may be made up of 4 groups of 2 (12 volts) which will leave you with a 24-volt system yet 4x the power stored.
Therefore the more groupings, the more available storage space, yet obviously the greater the cost. This is why it’s good to have a rough idea of your energy requirements.
Batteries For Living Off The Grid: Our Battery Bank System
Now, there are many formulas to use to help you calculate your battery bank requirements. They’re efficient and factual.
For the purpose of this article though, they give too much information and take too much time to calculate. So here’s a real-world example of how we live.
We have a two-story house and run a combination of solar, generator, and propane to power and heat the house.
I’ll break down the exact specifics regarding the generator and propane in a future blog post. Suffice it to say, we’re running a 24-volt system.
We were originally set up as a 12-volt system. This was based on a dozen 6-volt batteries each paired together so we had 6 groups of 2 batteries.
This worked well for our general lighting but was more challenging when operating appliances, pumps, and small tools.
We decided to change the configuration to a 24-volt service that only required changing the configuration to 3 groups of 4 batteries. Each group totaled 24 volts (4x6) and we have three series of 24 volts running parallel which triples the amps for a 24-volt system.
We did this more for convenience since our water system includes running a lake pump for water that requires 24 volts and cannot operate on a 12-volt system. Previously when running the pump, we had to also run the generator at the same time and switch the system to directly run from the generator.
I am always thinking about upgrading our batteries. Yet as previously stated, such things are contingent on available finances!
On Christmas Eve, 2019, our 40-year-old generator shed burned to the ground. That was the end of our Lombardini generators. We now (finally) have a new 11.5 kW Kubota diesel generator and Tesla 2 Powerwall/Solar panels setup.