Home Battery Storage for Solar Power

There are so many battery technologies out in the marketplace it’s highly likely that between me writing this and you reading it there will be another new fangled “world’s best battery” that has hit the market.

What Elon Musk has done with Tesla is to create a market awareness of home battery storage and the need to reduce our impact on the environment from burning fossil fuels. This has been fantastic for raising the level of awareness.

Is installing home battery storage actually the best thing for the environment though? As any good permaculture teacher will tell you: “Well, it all depends on the situation.”

My experience with batteries is that all the technologies have a place and purpose; it’s about choosing what’s right for you and your situation. It’s about choosing the right tool for the job and understanding the capabilities of that device. Not choosing the correct tool for the job can result in a broken machine!

This week I got the inside on the Tesla Powerwall as I attended a training session about installing home battery storage from the distributor of Tesla Powerwall in Australia. It was a fascinating look at what can and can’t be done with the technology and its limitations.

The three top batteries sold around the world for battery storage are lithium, lead acid, and nickel-iron cells. Australia is the largest installer of nickel-iron cells around the world currently for stand alone solar applications.

Let’s start with the number one selling battery worldwide: the lead acid battery.

Lead acid batteries

Lead acid cells have been the biggest selling batteries for home energy storage as they have been the most cost efficient and simple cell to use. Being the battery of choice for cars has helped bring down the cost of production. A lead-acid battery is made up of two-volt cells. Your car battery, for example, will have six two-volt cells joined in series, and that will give you a 12-volt battery. The most common thing in your car battery that fails will be a cell, and unfortunately, you can’t replace the one cell. The reason, in larger systems, you get individual cells is if one fails you can replace the one cell and it also makes the system easier to move around as lead is quite substantial.

You can get a lead acid battery to last 25 years and, yes, you can build a system out of them using 12-volt car batteries.

The key to getting them to last a long time is to only run loads like lights, computers, fans, televisions and energy-efficient refrigerators, and avoiding items that have a significant power draw at a high speed like kettles, toasters, ovens, microwaves, irons, and electric hot water systems. A good rule of thumb is, if it heats or cools it will want lots of energy fast.

If you’re going off-grid, the majority of the power-hungry devices can be sorted out by a installing a fireplace and using landscaping to cool your property. Most off-grid systems will also have a generator of some kind for backup. It’s best to run any of the energy hungry appliances directly from your generator as it will make everything last longer. If you have the grid available, using the network as your backup or running the massive loads directly from the grid will save your batteries.

The key to getting your lead acid cells to last is to keep them well charged and only use 30% of their capacity, only use light loads and understand how your appliances work. If you do, a good set will last as long as your solar panels.

Nickel-iron batteries

Nickel-iron and nickel-cadmium cells both last a very long time. Nickel-cadmium cells are not that attractive due to dealing with the cadmium at the end of their lifecycle. Nickel-iron, on the other hand, is nickel and iron, with the NiFe cells name coming from the periodic table. The electrolyte in a NiFe cell is alkaline-based potash: just distilled water and potassium hydroxide. This is a commonly used plant fertiliser. Your biggest decision when getting rid of the electrolyte once neutralised is deciding where you are going to grow your pumpkins and jerusalem artichokes. They both love potash.

These batteries are very robust, and you can use anything on them. They will not be damaged by overcharging or undercharging. They are, in my opinion, one of the world’s most environmentally friendly batteries on the market and one of the best all-rounder cells to use in a home storage system.

The downside to these cells is they off hydrogen gas, so it’s important to keep them in a well-ventilated space so they will not be able to create a build-up of hydrogen. You will also need to top them up with distilled water on average about 8-10 times a year, depending on how hard you use them. The biggest problem people have with them is the combination of the right technology using inverters and solar charge controllers.

Lithium batteries

Lithium has taken off, and with the help of Elon Musk’s passion for taking over the world with solar-powered electric cars, has boomed.

Lithium batteries are light and energy dense; they charge smartphones, cameras, electric vehicles and anything that is a considered a handheld device. Lithium is ideal for all of these uses.

The most important thing about lithium is the BMS (Battery Management System),and that there has been no faults in the manufacturing process. Check out some fun and educational videos on exploding phones at Lithium Batteries

Most of the handheld devices we own and use have been designed such that, before they get to the danger stage of fail of the battery. we are up for a new device anyway. One of the issues I see with using lithium in home energy storage is having a lithium battery permanently connected to a charger such as your solar panels on your house . If the BMS fails it will soon overcharge the batteries, and you will potentially have an explosion. A 7kwh Powerwall will have a very different bang to a smartphone battery!

It’s true that lithium batteries have a range of protective features to prevent this, and using one in parallel with the grid is one of those essential protective features. Most lithium battery manufacturers will not allow their batteries the ability to work completely standalone at the moment without the grid. There are also lots of brands of lithium batteries available other than the Powerwall.

Lithium is an ideal technology for running light loads, similar to the lead acid batteries, such as lights, televisions, energy-efficient refrigerators and so on. They are good for use in units, apartments, townhouses and in places where the grid is available and you can rewire your home only to run what I call your critical loads. This will make the battery last a lot longer and ensure some environmental benefit from installing it.

If you use a lithium battery and run ovens, air conditioners, kettles/jugs and heavy loads, you will be buying a new battery before it ever pays back its embodied energy or your bank account.

Currently, very little lithium is recycled due to the cost of doing so. This is the reason I call it the plastic bag of the battery world.

The best thing you can do for yourself and the environment is to reduce your energy demand. It will save you money straight away, reduce the use of fossil fuels and, when putting in a home solar system with batteries, you will be installing a smaller one as you don’t have a large load to support. Check out this video to help you do that for free.

To learn more about how to take control of your energy requirements, you can attend a hands-on workshop or subscribe to our YouTube channel for videos to help you on your journey.