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The best solar storage batteries: Tesla Powerwall and more put to the test

An independent trial compares solar storage batteries in lab conditions, and not all survive.

Solar storage batteries
Last updated: 29 October 2021

If you've got solar panels on your home, or you're considering getting them, then you're probably wondering if you should get a storage battery as well – and if so, which one is best?

An independent trial of solar storage batteries has been running in Canberra since 2016 to see how well they meet their performance claims over time. Batteries from Tesla, LG Chem, Alpha ESS and others were put to the test by ITP Renewables, and not all survived. 

Here's a summary of results from the first two phases of the three-year trial. In 2020, a third phase started with a batch of new batteries, but it's too soon to report on them.

About the solar battery trial

Our solar battery buying guide explains the general details of what to consider and whether a battery is likely to be cost-effective. But does a Tesla Powerwall beat an LG Chem battery? Should you go with other brands, or non-lithium types like Redflow? And do they all really meet their performance claims? Sounds like we need a comparative test under controlled laboratory conditions! Unfortunately, while CHOICE labs excel at product testing, a test of these batteries is far too complex and expensive for us to undertake.

Fortunately, someone else has done the work. ITP Renewables, a renewable energy consulting and project management company, has been running a battery trial in Canberra since 2016. With major funding grants totalling $870,000 from the Australian Renewable Energy Agency (ARENA), they built a test facility and have been testing storage batteries to an accelerated program designed to measure performance and reliability under typical Australian conditions.

Lessons for consumers from the solar battery trial

  • Malfunctions are all too possible with a storage battery.
  • Some battery manufacturers have already exited the market, and new ones keep appearing.
  • If you get a storage battery, you're best to stick with major brands to ensure good warranty support.
  • Installation by an experienced solar battery installer is a must.

Storage battery technology is complex and still evolving, as is the industry itself. The trial has demonstrated that there's a fair chance that a battery bought today will be obsolete within a few years – or worse, it might malfunction. Obsolescence is not a problem in itself as long as the battery keeps on working as claimed. But also, some manufacturers and distributors might not still be around to honour warranty claims – something that happened during this trial. 

Apart from the possible technical issues, it's still the case that batteries don't yet make full economic sense for most households, though we expect that to change in the next few years. We recommend you do your sums carefully to understand the economics for putting one in your home. That said, many people are investing in a battery regardless of the marginal economics in order to give their home more energy security and become more independent from energy companies.

If you do go ahead and get a battery, it's important that it's installed by experienced technicians who are familiar with the individual requirements of the product. As with any solar installation, look for a CEC-accredited installer – in this case, look for one who has specific accreditation for battery installation. You can also use our Solar Estimator tool (in partnership with SolarQuotes) to get quotes from reliable installers in your area.

Good warranty support is also essential, so we advise sticking with major brands who you can expect to still be around in 10 years.

Solar battery trial results

  • Several batteries failed in testing, while others have run with no significant problems.
  • Only one battery from the original Phase 1 set from 2016 is still running (Sony Fortelion).
  • Some other Phase 1 models ran OK but were eventually retired from the test as their test period was over and space was needed for newer batteries.
  • Two batteries from Phase 2 have run without major problems (GNB Lithium and Pylontech), while some others are still in the test but had to be replaced at different times due to problems (BYD B-Box, LG Chem HV, Redflow and Tesla PowerWall 2).
  • Several batteries had major failures (with either the battery itself, or essential manufacturer support) and were either removed from the test or replaced with new samples.
  • A new batch (Phase 3) entered testing as of early 2020.

Overall, it's disappointing how many of the batteries failed at different stages of testing. That said, some batteries have proven to be sturdy and reliable, and support from several of the manufacturers has been good, which is encouraging.

Top performers

Here are the solar battery models that demonstrated superior performance.

  • The Sony and Pylontech battery packs demonstrated superior capacity retention – that is, their claimed capacity didn't significantly diminish over time.
  • The Sony, Samsung, Tesla PowerWall and PowerWall 2, BYD and Pylontech have shown generally good reliability.
  • The Samsung and BYD have shown consistently high efficiency. This is a measure of how much of the energy put into the battery is actually stored and able to be extracted for use again.

Individual problems and results for each battery are detailed below.

Tesla  Samsung batteries

Tesla and Samsung batteries showed high reliability in the solar battery trial.

List of batteries in the test

Phase 1 of the test started in 2016 with eight batteries that were available at that time, and Phase 2 added another 10 models in 2017. Phase 3 batteries began testing in January 2020. Most of the batteries are lithium-ion – the most common battery chemistry available – but some other types such as lead-acid and flow batteries are included.

Each battery consists of battery cells plus a battery management system (or BMS – this is built-in hardware and software which manages the cell charge levels, voltages and so on). Most do not come with a built-in battery inverter (the device which actually controls power flowing to and from the battery).

Battery Trial phase Country of origin Chemistry Total Installed Capacity (kWh)
CALB CA100 1 China Lithium Ion (Lithium Iron Phosphate) 10.24
EcoUlt UltraFlex 1 USA Lead Acid Carbon 14.8
GNB Sonnenschein Lead-Acid 1 Germany Lead Acid 15.84
Kokam Storaxe 1 Korea Lithium Ion (Nickel Manganese Cobalt) 8.3
LG Chem RESU 1 1 Korea Lithium Ion (Nickel Manganese Cobalt) 9.6
Samsung AIO10.8 1 Korea Lithium Ion (Nickel Manganese Cobalt) 11.6
Sony Fortelion 1 Japan Lithium Ion (Lithium Iron Phosphate) 10.24
Tesla Powerwall 1 USA Lithium Ion (Nickel Manganese Cobalt) 10.24
Alpha ESS M48100 2 China Lithium Ion (Lithium Iron Phosphate) 9.6
Ampetus Super Lithium 2 China Lithium Ion (Lithium Iron Phosphate) 9
Aquion Aspen 2 USA Aqueous Hybrid Ion 17.6
BYD B-Box 2 China Lithium Ion (Lithium Iron Phosphate) 10.2
GNB Sonnenschein Lithium 2 Germany Lithium Ion (Nickel Manganese Cobalt) 13.6
LG Chem RESU HV 2 Korea Lithium Ion (Nickel Manganese Cobalt) 9.8
Pylontech US2000B 2 China Lithium Ion (Lithium Iron Phosphate) 9.6
Redflow Zcell 2 Australia* Zinc Bromide Flow 10
SimpliPhi PHI3.4 2 USA Lithium Ion (Lithium Iron Phosphate) 10.2
Tesla Powerwall 2 2 USA Lithium Ion (Nickel Manganese Cobalt) 13.5
BYD B-Box HVM 3 China Lithium Ion (Lithium Iron Phosphate) 11.04
DCS PV 10.0 3 Australia/ China/ Japan Lithium Ion (Lithium Iron Phosphate) 10
FIMER REACT 2 3 Italy/ Japan Lithium Ion (Nickel Manganese Cobalt) 8
FZSoNick 3 Switzerland Sodium Nickel Chloride 9.6
PowerPlus Energy LiFe Premium 3 Australia Lithium Ion (Lithium Iron Phosphate) 9.9
SolaX Triple Power 3 China Lithium Ion (Nickel Manganese Cobalt) 12.6
sonnenBatterie 3 Germany/ Australia Lithium Ion (Lithium Iron Phosphate) 10
Zenaji Aeon 3 Australia/ China Lithium Ion (Lithium Titanate) 9.6

* Designed and assembled in Australia; battery manufactured in Thailand.

How each battery performed

Products are listed below in alphabetical order. Typical problems encountered include:

  • operational failures such as the battery shutting down unexpectedly
  • lack of manufacturer support for technical issues
  • accelerated capacity fade (the capacity of the battery is how much energy it can store – it's expected to decline in an orderly fashion over several years, but for some models their capacity faded faster than it should)
  • poor performance during summer temperature tests – batteries don't generally like extreme temperatures, but these models should be expected to cope with a wide range of climates.

How the solar battery trial is run

SMA Inverters

SMA inverters were used in the test of solar battery storage.

A climate-controlled fire-proof test room was built and the batteries installed inside it, connected to inverter units on the outside. Power is supplied from the mains grid. The aim is to cycle (charge and discharge) each battery three times each day, which over the three-year trial is roughly the equivalent of nine years of use in a typical setting.

This is more cycles per day than the batteries would experience in normal use, but the program isn't designed to stress the batteries unnecessarily. That said, the accelerated test program may have affected some batteries more than others.

Read the full reports for each stage of the trial.

Possibly the major lesson for CHOICE is that running a battery test is just as challenging and fraught with unexpected outcomes as we thought, and we're very glad ITP did it instead.

Faulty and discontinued products

The battery trial encountered a number of technical challenges, including several batteries developing faults and having to be removed or replaced. Some models are no longer available, as companies collapsed or withdrew from the battery market. This illustrates how relatively new this technology and industry still is. The industry has already matured significantly since the battery test began and we expect this will continue, and new entrants and new technologies are also appearing.

Inverter integration

Integrating batteries with suitable inverters also proved problematic in many cases, in particular with the battery-inverter communications interface.

The trial has also demonstrated how difficult it is to devise a single test regime that covers several different battery chemistries, as they each have different performance limitations. It's likely that the test regime works better for lithium-ion batteries than for lead-acid, for example.

The trial continues

The battery trial is ongoing, and testing for some of the models above has now completed, while others continue on. New batteries have been added in a new round of testing (Phase 3) but these haven't yet been through enough cycles to have useful results. We aim to update this article when the Phase 3 batteries have been through enough testing to draw useful conclusions.

The new batteries added in Phase 3 are:

  • BYD B-Box HVM 
  • DCS PV 10.0 
  • FIMER REACT 2
  • FZSoNick 48TL200
  • PowerPlus Energy LiFe Premium
  • SolaX Triple Power
  • sonnenBatterie
  • Zenaji Aeon.

Acknowledgement

Our thanks to ITP Renewables for their assistance in producing this summary.

We care about accuracy. See something that's not quite right in this article? Let us know or read more about fact-checking at CHOICE.