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The 6 Golden Rules to Choosing the Right Battery for Your Solar System

The advances in deep cycle rechargeable batteries is the most exciting, cutting-edge aspect of solar technology.

Their ability to store self-generated power during the day to help even out evening peak times and provide energy while the sun’s not shining makes the opportunity for less reliance on the grid and even more savings a really attractive prospect for those interested in solar power.

Even Transpower, in a recent report on the future of energy production and distribution in New Zealand, says that their business will change within a few decades “from providing 24/7 reliability and real-time balancing to providing a resilient battery-charging service.”

So if batteries are the future of both domestic and commercial power, what are the current options and what are their benefits?

1. You don’t have to wait for technology to catch up.

We’re always going to have those keen early-adopters buying into battery technology, but the key message for people investing in a new solar system is to invest in a system which is “battery ready”. Harrisons Energy Solutions Managing Director Phil Harrison says the prices of panels and inverters have come down a long way in recent years but are unlikely to fall further until capacity grows – batteries, on the other hand, are due to fall in price by around 15% each year over the next few years. “Most people are looking at what’s happening to battery technology in the next few years but want a system now that’s battery-ready now,” says Phil. “So that when batteries come down in price it’s not a complicated or expensive exercise to then add a battery on to their system.”

2. Cycle life is vital.

This determines the number of charges a battery will provide before its capacity falls to a predetermined percentage. It’s important to compare batteries marked as having similar capacities against their cycle lives as this is the ultimate mark of quality.

3. Getting a battery doesn’t mean the same as living off-grid.

Phil says a 7 or 10kWh battery will be more than adequate for a typical New Zealand household to maximise their storage and power savings – and these are part of grid-tied systems that generate power during day and send any surplus power back to the grid. “With a battery, this power will be sent to their battery for the two times during the day when there’s usually peak power (when you’re home from work and first thing in the morning). The battery is designed to get them through the night time, it’s not looking to eliminate their power bill. Instead it’s looking to maximise the savings on their power bill from say 30-40% at the moment to say 70 to 80%. Most people will only really want to go off-grid if they live in truly remote areas and connection is too expensive or if they want complete independence from the power companies.”

4. Don’t underestimate the amount of electricity you require.

The battery’s capacity is important because it marks the amount of energy you can store – so you must judge correctly your home’s power needs and how much you can save with solar. And, according to Phil, that means having a look at what your home is likely to look like in five or ten years’ time. “Solar doesn’t offer one solution for everyone – it involves what power you’re consuming, when you’re consuming it and what you want to do in the future,” Phil says. “So it’s not just putting panels in the roof to power appliances in your home, if you look at our homes in five or ten years’ time it might seem crazy now, there’s going to be a pendulum shift in how we all use electricity. So you might have an electric vehicle and you might power that up at home, or you might use the battery in the vehicle to run the power in your home; or your house will have all the smarts to turn on the power and know when not to use it by looking at weather forecasts; or all your appliances will ‘talk’ to each other and be intuitive. All these things are effectively happening now, it’s just about getting it all packaged up so that it’s user-friendly and cost effective and we’re not years away from that anymore.”

5. The true cost isn’t just the price on the label.

While the cost of batteries is falling all the time, they are still a sizeable investment in any PV solar system. But as well as comparing prices, it’s important to see the value of avoiding a cheaper, undersized battery (that fails to fulfill needs and maximise savings), or a poor-quality battery which requires more frequent replacements and may not be safe. The main two players in battery technology are Tesla (which uses Panasonic technology) and LG Chem and because they are both the leaders and innovators in the field, their products have the best mix of price and quality. Harrisons Energy’s decision to work with LG’s batteries is, says Phil, because their technology suits New Zealand’s climate and consumers. “Tesla and LG will be the leaders in terms of technology and price because of scale,” he says. “You already see a lot of batteries coming out of China and you have to be careful because of the safety of lithium ion batteries – you have to have all your boxes ticked. We’re pretty keen on LG Chem because it will be competitive to Tesla and it’s smaller and very cool technology. The first generation batteries are already in the market and the second generation models will reach here later this year which is probably two years earlier than we thought and at prices that we didn’t think were going to happen for another two years, so it’s really created a buzz globally.”

6. Know your options

There’s plenty of makes and styles of battery so it pays to do your research: quality cycles during a battery’s lifetime and are both efficient and lose little capacity while not being used but need to be monitored to prevent excessive charging and are difficult to recycle. These are the batteries most people are using for home, grid-tied solar systems and the ones being championed by LG Chem and Tesla. and with a shorter expected lifetime. But new innovations have increased performance and energy output making both gel and absorbed glass mat (AGM) more user-friendly. Used mostly for off-grid systems. grid storage at power plants but developers are working to bring down both the size and the cost for domestic use. Manufacturers point to longer lifespans, safety, recyclability and the ease of up-sizing batteries once they’re in use as their major plus-points but they are still most likely to be used for off-grid systems.

  • Lithium-ion: These are the most common form of battery used for smartphones, power tools and electric vehicles. They provide a high quality cycles during a battery’s lifetime and are both efficient and lose little capacity while not being used but need to be monitored to prevent excessive charging and are difficult to recycle. These are the batteries most people are using for home, grid-tied solar systems and the ones being championed by LG Chem and Tesla.
  • Lead acid: The sort of batteries you’re used to seeing in vehicles are much more cumbersome than lithium-ion batteries, less efficient and with a shorter expected lifetime. But new innovations have increased performance and energy output making both gel and absorbed glass mat (AGM) more user-friendly. Used mostly for off-grid systems.
  • Redox flow: Because of the complex chemistry and mechanics involved in running these batteries they are currently mostly in use for grid storage at power plants but developers are working to bring down both the size and the cost for domestic use. Manufacturers point to longer lifespans, safety, recyclability and the ease of up-sizing batteries once they’re in use as their major plus-points but they are still most likely to be used for off-grid systems.

Phil says there are other types of technology in the solar market, but because LG Chem and Tesla are forging ahead with lithium-ion, that’s the technology that is most likely to fit in with the rest of the system technology. “Lithium-ion is the same technology as they use in electric vehicles so it ticks boxes in terms of size, output and capacity,” he says. “Twelve major car companies have partnered with LG to supply batteries for their cars and Tesla’s new giga-factory will double the world’s production from just one factory, so once you’re getting that scale happening as well as technological advances then prices will come down significantly. But there’s no need to wait until then. We don’t want people thinking they’ll hold off until batteries come down in price, you’re better to go solar now and make savings right from day one while still having a system that is ready for a battery.”

For more information about how you can start making savings to your power bill and to discover which system fits your household’s requirements, you can contact Harrisons Energy on 0800 003354 or via the website.