• Fayaz Ahmed

The Battery Comparison: Tesla Powerwall 2 vs Sonnen ECO

Home battery systems installations around the world are projected to exponentially increase over the coming years due to a combination of factors (i.e. plummeting battery costs, government incentives and high power prices.)

According to the latest forecast from research company BloombergNEF (BNEF), battery prices, which were above $1,100 per kilowatt-hour in 2010, have fallen 87% in real terms to $156/kWh in 2019. By 2023, average prices will be close to $100/kWh.

When it comes to manufacturing different battery chemistries within Lithium ion family of batteries. Following companies are the prominent and leading players:

· LG chem (South Korea)

· Tesla (United States)

· Sonnen (Germany)

· BYD (China)

· Pylon Tech (China)

· Simpliphi Power (United States)

However, in this piece, I am only comparing the AC batteries from Tesla and Sonnen.

Tesla Powerwall 2 vs Sonnen ECO

Unless you've been living under a rock, you'd know about the success of Tesla and Powerwall 2. But Tesla is far from the only company looking to profit off of rechargeable batteries for the home.

If we talk about expertise and experience in battery storage industry Sonnen is also not behind any battery storage industry juggernauts (i.e. Tesla, LG Chem, BYD.) Sonnen battery systems proven performance and great warranty easily places them in the same league as both Tesla and LG Chem, although some argue they are even better.

Here are some key differences between them:

Battery Size:

The good thing about Sonnen ECO is that it is a modular system made up of 2.5 kWh battery modules whereas storage capacity starts from 5 kWh (2 x modules) up to 15 kWh maximum.

On the contrary, Powerwall 2 of Tesla comes only in one size (13.5kWh storage capacity) which should be well sized for most large modern homes. Furthermore, It’s also the only battery to incorporate liquid cooling which may mean it outlasts other batteries, especially in hotter climates.

Battery Chemistry:

Other most important difference between Sonnen ECO vs Tesla Powerwall 2 is the use of different battery chemistries. Tesla uses Lithium Nickel Manganese Cobalt Oxide (NMC) for Powerwall 2 as opposed to Lithium Ferro Phosphate (LFP) of Sonnen ECO.

There is no need to go into the details of these battery chemistries definitely both of them have their own benefits and drawbacks but something which is worth mentioning is that of all the lithium battery chemistries available the Lithium Iron Phosphate (LFP) batteries are the least toxic as they do not contain Cobalt. LFP batteries are also considered the safest chemistry with the longest life and lowest risk of thermal runaway if damaged or overheated.

Battery Power Ratings:

Talking about power output, the lithium NMC batteries used by Tesla have a higher discharge rate which equates to higher power output at 5kW continuous, compared to a maximum of 3kW power rating from the Sonnen ECO.

The power output of Sonnen ECO is rather limited at 3.3kW charge and discharge. This means a larger 15 kWh capacity battery could take 4 hours or more to charge which may be problematic during short winter days, or if shading is an issue.

Battery life:

In terms of life span and warranty, the Sonnen ECO battery uses longer life Lithium LFP (Lithium Ferro Phosphate) battery cells and comes with one of the best warranties on the market, with an estimated 88% retained capacity after 10 years. The Powerwall 2, on the other hand, uses Lithium NMC cells similar to those used in the electric vehicles, with an estimated minimum 70% retained capacity after 10 years.

Like most other reputable battery supplies the Sonnen ECO warranty comes with a 10 year warranty but it beats most others in that it also covers 10,000 charge/discharge cycles to 80% retained capacity. This is very impressive and only high quality lithium cells with robust monitoring and balancing could achieve this. Ten thousand cycles is huge and no doubt the ten year period will come before this number of cycles is ever reached, even with 2 cycles per day this would take about 13.7 years.









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