Did you know you can use a lithium battery bank to power everything from fishing kayaks, RVs, to off-grid vacation cabins? Lithium batteries are reliable and versatile. But you can’t use the same battery capacity to power a single navigation lightbulb in your boat as you would to power all the appliances in a house. Try that, and you’ll run out of power in no time.
That’s why it’s important to figure out how much battery capacity you require. Once you do that, you can create the perfect battery bank for your needs.
What is a Battery Bank?
A battery bank consists of two or more batteries connected together. They may be connected via series wiring or in parallel. Doing this allows you to have a larger energy storage capacity, and power your devices for a longer period of time. Battery bank sizing refers to the number of batteries you’ll need, and what size they should be.
How to Determine Battery Bank Sizing
It might seem like a daunting task at first to figure out your battery bank sizing. That’s especially true when you have large energy requirements, like powering everything in an off-grid house.
But here’s some good news: every electronic device will tell you its electrical load draw. Just look at the label or packaging. You can use this information to figure out your total energy requirement. That’s the first step to determining battery bank sizing.
So go grab a pencil, paper, and calculator (or an electronic device if that’s more your style). Take a look at the electrical load draw of each device you want to power. Then use the steps below to find out how much capacity you need for your lithium battery bank.
Step 1: Calculate Your Daily Energy Load
Look at the electrical load draw on each device. It should be in amps or watts. If it’s in amps, multiply that number by the number of hours you’ll use it per day. That’s your amp-hour requirement. You can add the daily amp-hour requirement of all devices together to get your total daily energy load.
What if it’s in watts? First, you need to divide the watts by the voltage to get the amount of amps. Then multiply the amps by the number of hours you expect to use your device per day. Finally, add up the amp-hour requirements of each device to get your total energy load.
Want to go off grid and power your house with solar and a battery bank? Take a look at your utility bill. You can estimate your energy demand by looking at how much energy you used throughout the year. Don’t forget to account for the months you have higher demand.
Step 2: Create a Lithium Battery Bank to Handle Your Energy Load
Now that you know your amp-hour requirement, you need to make a lithium battery bank to handle that load.
For example, if you need a total of 40 amp hours to power a 12 volt application, you can connect two 12V 20Ah batteries together in parallel. When you connect batteries in parallel, the amperage adds together, and the voltage stays the same.
If you connect batteries in series, you can increase the voltage. For example, let’s say you have a 24 volt trolling motor. You could make a lithium battery bank of two 12V 100Ah batteries in series, plus one 12V 125Ah to take care of the engine starter and other onboard equipment.
Other Battery Bank Sizing Considerations
Batteries don’t create energy–they only store it. So it’s important to make sure you have a way to charge your lithium battery bank.
There are a few ways to do this:
- A charger connected to the electrical grid
- A generator
- Solar power
Let’s say you have a 200Ah lithium battery bank, but your solar panels don’t generate enough energy to fully charge it. Your bank won’t be able to provide 200Ah, and you’ll run out of power. In that case, you will have to get more or larger solar panels, or reduce the amount of energy you use.
The good news? Unlike lead acid batteries, a lithium battery bank won’t suffer any damage when partially charged. So the occasional cloudy day is no big deal. However, if your batteries are consistently undercharged, you’re paying for battery capacity that you’re never going to use. In that case, it’s better to choose a battery bank with less capacity that you know you can fully charge.