Picking the right battery and paying the right price

A buyer’s guide to solar batteries

By Maz Mirzakhani

Mechnical Engineer, SolarNova.

In recent years some solar batteries have become far more affordable and more and more Australians are choosing battery energy as part of their solar system. The battery energy storage industry is constantly evolving and the leading companies in the market are competing for a larger share of the market.

There are dozens of battery storage companies, including many chinese brands, however the market is dominated by the big four battery storage companies; Tesla ( American), LG Chem (Korean), Sonnen (German) and BYD (Chinese).

In this article we will go through these top 4 brands and explore them to understand some of their battery features and specs with pricing.

The big 4 solar battery brands

Tesla is an American automotive and energy company based in California. The company specialises in electric car manufacturing and, through its SolarCity subsidiary, solar panel and battery storage manufacturing. They started with Tesla Powerwall (7 kWH) back in 2015 and launched Powerwall 2 (13.5kWH) in 2017.

 LG Chem is a large subsidiary of LG Electronics based in South Korea and offers a wide range of energy storage solutions to the market known as the LG Chem RESU models.

Sonnen is one of the biggest battery manufacturers in Europe and is headquartered in Germany.

The company has recently announced its 9th generation Sonnen Batterie Eco available in multiple power sizes.

BYD Co Ltd is a Chinese manufacturer of automobiles, battery-powered bicycles, buses, forklifts, rechargeable batteries and trucks,  with its corporate head office in Shenzhen China.

The BYD battery storage B-Box HV series is a sleek and stylish solution that is perfect for the average sized Australian household.  BYD’s modular architecture means households get a  storage solution customized to their unique requirements.

Let us analyse each of these products so you can better understand how their respective features and benefits fit with your needs and which offer you the most value for money.

  1. Solar battery warranty

Compare the warranties

Tesla

The Powerwall 2 warranty has two categories.

  1. The first is for Households who only charge it using sun generated solar power.  In this case the warranty  lasts for 10 years and has unlimited cycles, meaning you can recharge it as many times as you like.  Unlimited cycles sounds wonderful, and it certainly isn’t bad, but only charging off solar means people who are on-grid and have time-of-use tariffs won’t be able to charge it using low cost off-peak grid electricity, while people who are off-grid won’t be able to charge it using a generator.  This means the Powerwall 2 does meet the need of most Australian households who still want to recharge their batteries using the grid or generators.
  2. The second category allows a Powerwall 2 to be charged using power other than solar, but the warranty is limited to 10 years or a total of 37 MWH of stored electricity – whichever comes first.

LG

LG Chem RESU 7H and 10H products guarantee that the battery will retain at least 60% of its nominal energy output for 10 years, or for a minimum energy throughput from the battery, whichever comes first.

According to this statement, the LG Chem RESU 10H model that has nominal energy storage of 9.8kWh which ensures that the product will be able to store at least 5.88 kWh by the end of the 10 years or provide 27.4MWh of energy throughout.

Sonnen

Meanwhile, the Sonnen Batterie Eco 9.43/10 has a nominal battery capacity of 10 kWh (similar to the LG Chem product) and guarantees that the product will maintain at least 70% of its capacity to hold a charge or run at least 10,000 cycles, whichever happens first.

BYD

BYD battery warranties are the same as the LG chem RESU battery warranties.

  1. Chemistry and Physical Dimensions

Compare the battery chemistry and dimensions

Tesla

Tesla Powerwall 2 with 13.5 KWH energy storage is 115 cm in height, 75 cm in width and 15 cm in depth and weighs 120 kg. It is a wall mounted design. Its sleek design is sought after by many who value how the battery will look installed. Its chemistry is lithium Ion cobalt.

LG

LG Chem RESU 10H energy storage battery is 90 cm height, 74 cm in width and 20 cm in depth and weighs 100 kg. Its chemistry is Lithium ion Phosphate.

Sonnen

The Sonnen 9.43 10kWh battery, is 186 cm in height, 67 cm wide, and 23 cm in depth. The battery configuration changes as you add additional cells of 2.5kWh capacity, and the weight changes accordingly. Sonnen’s 10kWh battery is heavy, weighing154 kg. Its chemistry is Lithium ion Phosphate.

BYD

The BYD Battery – Box H10.24 , is 125 cm in height, 58 cm in width and 38 cm depth and weighs a heavy 226 KG. These batteries come in 8 modules of around 27kg each, which are added to a base and the top section BMS unit. They don’t need a cabinet as it is easy to stack them and very easy to install. Its chemistry is lithium ion phosphate.

  1. The Inverter compatibility and system design

Compare the inverter compatibility and system design

Tesla

Tesla Powerwall 2 comes with a built in inverter that means you have no need to buy an inverter to add the battery to your  solar system. It is simply connected to the AC part of the panels. Depth of discharge is 100% (it discharges at 13.5 kWH, which it is rated for).

The operating temperature is between – 20°C to 50°C with a power output of 7kW peak / 5kW continuous. It comes with internal liquid thermal control (which means it can stand up to extreme fluctuations in temperature.) It has a backup solution in case of a black out. When a black out occurs the system detects and disconnects from the grid to supply the power to the house. When the next day sun is out, it will charge the battery with panels power for the night time. It is designed for both indoor and outdoor installation.

LG

The LG Chem RESU 10H is a lithium-ion battery designed to be connected at 400 VDC nominal voltage and a maximum voltage of 520 VDC.

High voltages are always desirable because they can transfer the same amount of power using less electrical current, which also means less power loss. The ambient (surrounding) temperature should be within the range of -10 °C to 45°C) with a power output of 7kW peak / 5kW continuous.

Also, the battery nominal capacity is 9.8kWh, but its usable capacity is 9.3kWh. This translates into a maximum depth of discharge of 95%.

Moreover, the LG RESU models are designed to fit both indoor or outdoor environments without any additional enclosure. LG battery compatible inverters include; Fronius – Sungrow – SMA – SolarEdge and Huawei. LG Battery RESU 10H are designed for both indoor and outdoor installation. How a battery operates in black outs depends on the inverter type and model installed with the battery, see our Buyers guide to Inverters for a detailed explanation of different types, models and functionality. If you have frequent black outs in your local area, you might consider inverters with a back up feature. If you are in locations where  blackouts happen once or twice year for couple of hours,  you might consider the backup feature is not worth the extra cost.

Sonnen

Sonnen 9.43 10kWh model works with a lithium iron phosphate battery at a nominal voltage of 48VDC.

The depth of discharge of the battery is 90% which means that from a 10kWh nominal battery capacity model you will only be able to use 9kWh and the battery is only suitable for indoor spaces, meaning an additional expensive enclosure is needed for outdoor purposes.

An important comparative difference to the LG Chem RESU model, is that Sonnen, like Tesla Powerwall 2, comes with a built in inverter. It connects directly to the AC part of the panels without a separate inverter. Like Tesla Battery, Sonnen Battery has back up in the case of black out. During a black out it detects and disconnects from the grid to supply the power to the house and when the next day sun is out, it will charge the battery with panels power for the night time. The ambient (surrounding) temperature should be within the range of -2 °C to 65°C. The power capacity is only 3.3 kW for all 9th generation models, which is not a lot as it is a low voltage battery.

BYD

BYD Battery – Box H10.24 is a lithium-ion battery designed to be connected at 400 VDC nominal voltage and a maximum voltage of 450 VDC.

High voltage batteries are always desirable since they transfer the same amount of power using  less electrical current, which is also less draining on power. The ambient temperature should be within the range of -10 °C to 50°C) with a power output of 20kW peak / 10kW continuous.

Also, the battery nominal capacity is 10.2kWh, and its usable capacity is 10.2kWh. This translates into a maximum depth of discharge of 100%.

Moreover, the BYD H10.2 models are designed to fit both indoor or outdoor environments without any additional enclosure. BYD compatible inverters are from Goodwe– Sungrow – SMA and Huawei. BYD 10.2H batteries are designed for both indoor and outdoor installation. How the  BYD 10.2H performs in a black out depends on the type of Inverter that been installed. See our Buyer’s Guide to Inverters for more explanation of their functionality. If you have a frequently black out in your local area you might consider inverter’s  with back up feature. If you are in locations where blackouts happen once or twice year for couple of hours, you may conclude the backup feature is not worth the extra cost.

  1. Price

Compare the price

The price of battery has been gone up for some brands and down for others since last few year to August 2019;Tesla battery Powerwall2 13.5 kWH storage price has gone up from around $10,000 in 2017 and is now sitting around $16,000 –  the Sonnen Battery price has not changed since last few years sitting on $14,000 for 10kWH storage – LG chem battery price has dropped by 40 Percent over the last few years from $1,4000 to $8,000 for 10 kWh storage.

The price of battery is different to price for installed battery as you can see from the above the Tesla and Sonnen battery don’t need an inverter, whereas the LG and BYD battery need an inverter to install battery to system.

The table below is the estimate installed cost for the battery per kWH (the key metric when comparing batteries apple to apple)

Battery Cost fully installed per kWH
TESLA POWER WALL 2 (13.5 Kwh)$1200
Sonnen9.3 - 10 kWH)$1400
LG Chem RESU 10 H kWH$900
BYD 10.2 H$950

What size battery you need depends on how much energy usage you have in a peak time. It’s a lot easier to get the return on investment on panels than a battery as there is no rebate for batteries in NSW (there is rebate for some states; $6000 rebate in SA- $2000 rebate in VIC – $3000 rebate in QLD).

The price of electricity across the large majority of NSW is around 58c /kWH including GST at the peak time, so if you having a 10kwh battery charging and discharging once a day, the LG battery should pay itself in less than 5 years .

Conclusion

Choose the solar battery that is right for you.

We have found that the warranty offered by Sonnen is better than the one from the others, since Sonnen is guaranteed to remain at a minimum of 7kWh by the end of the 10-year period or 10,000 cycle whichever is sooner.

Regarding dimensions and weight, which can deeply influence transport costs, Sonnen are definitely much better with the LG and Tesla option, as they are compact and easy to install on the wall.

If we refer to the specs, we notice Tesla and BYD have 100 % depth of discharge, LG chem Resu has 95% depth of discharge, finally Sonnen with 90 % depth of discharge. With the exception of the Sonnen battery, all the other batteries can be placed in outdoor or indoor=. The temperature operating conditions all of 4 batteries cover most of the state’s temperature range.

Tesla and Sonnen battery have a black out solution while  the LG and BYD require an inverter to be installed with a black out solution capability.

In terms of power output, the Sonnen’s 9th generation products limit their AC power output to 3.3 kW, while LG and Tesla is 5kW, BYD- H10.2 power output is limited by the inverter output (the H10.2 battery itself has an output potential of 10kW power) .

Here a decision must be made as to whether it suits you to have 3.3 kW AC output or not.

We recommend all of the big 4 batteries. Sonnen and Tesla offers a really good quality product, but LG and BYD are also doing so. The question is if the extra price is worth it?

Some customer’s question the additional cost of Sonnen and Tesla, since the LG product will pay for itself much faster than Sonnen’s and Tesla Battery. A key to the consideration in your choice of battery is your household’s energy requirements to power your appliances at night or on cloudy days, using solar energy.

Next Step

If you want to see how much solar or battery storage could save you over the next 5 years, then take our solar saving calculator quiz below!

Or talk to an SolarNova expert about the best solutions for home energy storage or PV-panels.

Otherwise, head back to the SolarNova solar blog to find even more great educational content.

2 thoughts on “Picking the right battery and paying the right price”

  1. 10 kWh storage does that mean 1KWh for 10 hours, 2Kwh for 5 hours.
    How long will the batteries last
    Many thanks Shane Murphy

  2. Hi Shane,

    that is correct with 1 kW power draw will last 10 hours and with 2kW power draw will last 5 hours.
    all the batteries in the market come with 10 Years warranties. Every brand has their own terms for the life time, for instance Tesla has 10 years warranty and minimum 70% battery Capacity left in 10 years time which probably last another 5 to 10 years. Sonnen battery has 10 years or 10,000 cycle warranty whichever comes first.

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