Off Grid Batteries aka Solar Batteries store energy from electricity generators (solar panels, wind turbine, micro hydro turbine and back-up generators) so that you can use power at night. Basically, if the sun shone 24 hours a day you would not need batteries for your off grid system!
A large off grid battery bank can be as tall as your hip and take up the length of a carport. Others are smaller and could easily fit inside a small cabinet. The size of your battery bank depends on how much power you like to use. Generally, people living off the grid have batteries that range from 4kWh – 50kWh.
It’s important to be accurate regarding the amount of power you intend using when choosing the size of the batteries for your off grid system. You want to get it right first time because unlike solar panels you can’t just add a few more down the track.
Types of Solar Batteries
There is a wide range of different types of batteries available on the market, and they are normally defined by the chemistry that converts stored energy into electricity. When it comes to living off the grid, you have the option of either:
- lithium batteries, or
- lead acid batteries
Currently there is a lot of buzz surrounding the exciting potential of lithium batteries. These are mainly used in electric cars and a big advantage is that they are significantly lighter than lead acid batteries.
Many experts predict electric cars will become more popular and the cost of making lithium batteries will decrease with scale of production. The same battery can be used to power a house so with the price decrease, going off grid will get cheaper!
Lithium Batteries are a good alternative for what is referred to as Hybrid Systems. You need to be aware that Hybrid Systems are different to Going Off Grid Systems. Despite the hype around the future of lithium batteries, lead acid batteries are currently the best for solar power applications (particularly the Going Off Grid system) because they are the most cost effective and reliable.
The lead acid battery can be split into two categories for off grid application. These are:
- Flooded lead acid – these require constant refilling with distilled water.
- Sealed lead acid – these are sealed and so many describe them as ‘maintenance free’ because you don’t need to keep topping the electrolyte up with distilled water. Of course the convenience of not needing to re-fill these types of batteries means they are a little more expensive than their flooded cousin.
Comparing One Battery to Another
The best way to measure battery banks is in kWh’s as opposed to kW (the way to measure solar arrays). Sometimes battery banks are measured in Amp hours (Ah) and Volts (V). To make it easier to compare one battery bank to another it is best to convert the measurement into kWh.
You’ll see on the right of this page an image of Going Off Grid’s Battery Calculator. Click on the image to visit the calculator page where you can compare batteries.
Living with Your Solar Batteries
Nearly everyone in the modern world has experience with batteries. You are no doubt used to reading the icon on your mobile phone or tablet to see how full the battery is. When you are living off the grid you interpret the state of charge of your batteries in the same way by using a % sign.
When a phone battery needs charging you plug it into the wall or your car’s charger. When your solar battery needs charging it will automatically take electricity from the sun. But if you are using more power than expected or the sun has gone down, your battery gets a charge from your back up power system.
If you have calculated your electricity usage correctly and the batteries are the right size there should be enough power to get you through a normal night without using the back up generator.
A good hint with regards to Solar Batteries is that the closer their charge stays to 100%, the longer they will last. Making a habit of using power when the sun is shining means you can use power directly from the solar panels rather than cycling the batteries.
A Frequently Asked Question: What does ‘cycling the battery’ mean?