It’s a question central to electric vehicle (EV) leadership: Who’s leading on the battery front? We’ll leave GM & LG Chem out of it for the time being, but a recent comment (+ referenced article) here on CleanTechnica brought up the question of BMW+Samsung batteries vs Tesla+Panasonic batteries, and it seemed worth discussing.
Unfortunately, we don’t have enough data to do a complete comparison of the different battery cells and battery packs used in Teslas vs the BMW i3, but I think we have some good guidance.
Price/kWh Is Critical*
The single most important component of an EV for cost-competitiveness is the cost+number of its batteries. If the carmaker has access to low-cost batteries, it can produce a car that is superficially competitive with gasoline cars in terms of the balance between upfront price and features/size, while also providing long enough range that it is acceptable for a normal consumer. (Naturally, if consumers are aware of all of the “deeper” benefits of EVs, a gasoline car can seldom compete with an EV, but consumers by and large are not aware of these benefits, so it’s generally a moot point.)
For years now, the research we’ve seen has put Tesla at the top of the list for the cost/kWh of its batteries (though, it was close to Nissan according to one estimate a couple of years ago). The most recent statements from Tesla put its battery pack costs below a surprisingly low $190/kWh — though, that’s also approximately what an estimated GM/LG Chem battery pack costs for the upcoming Chevy Bolt (based on GM’s announcement of $145/kWh LG Chem battery cells and an extra 30% estimate for the remaining pack costs, which brings a pack to $189/kWh).
Since Tesla and LG Chem are the only ones to have announced long-range electric cars for under $40,000, they’re the only ones we can solidly presume have contracts for batteries at a low enough cost to offer such cars. However, there’s plenty of hope that BMW and Nissan are coming to that point as well — but that they don’t want to undercut their current offerings by making their plans public.
For the moment, though, simply put: You can buy a large, fully electric, premium-class sedan with >200 miles of range from Tesla for $66,000 before incentives, and BMW’s subcompact (yep, subcompact) i3 costs $51,400 with under 100 miles of range. There are other factors at play as well — the i3 is made of rather expensive carbon fiber, for example, and the Model S comes with Supercharging — but it seems like a safe conclusion that BMW’s batteries are much more expensive than Tesla’s.
Price/kWh Isn’t Everything
Whether things or not are as we presume in the $/kWh side of the equation, it’s important to realize that kWh is only about initial rated capacity and doesn’t cover the full story.
Battery expert Denis Rakcheev, Founder and CEO of Versatile Energy Provider, recommended adding power density (kWh/kg) as a key parameter to consider. He summarizes:
Tesla modules are relatively cheap (one could find even cheaper lithium-chemistry batteries, but power and thermal performances of those batteries would not be great). However, Tesla’s cells are one of the most gravimetrically efficient.
The more the vehicle weighs, the more energy it will require to propel itself. Different manufactures took different approach to address this. Tesla went for a diplomatic approach: aluminum body and high-energy-density cells (140 Wh/kg, similar to the Nissan Leaf battery). BMW i3 has one of the lightest bodies, made of carbon fiber, but rather-low-density cells (95 Wh/kg), while Kia Soul EV has an ‘old school’ heavy steel frame but extremely dense lithium-polymer cells (200 Wh/kg). Thus, ideally for the customer would be a vehicle with all these advantages, maybe Faraday Future?
(Just to give a small insight on small players and startups: in our project, VEP-Tech, we use cells with 112 Wh/kg and 210 €/kWh. From Samsung SDI, by the way.)
Aside from power density, and also aside from but related to price per kWh of initial capacity, if batteries could only be cycled (fully discharged and charged) 10 times before losing 20% of their capacity, they’d be big losers and the car companies and models using them would be in the junkyard.
This is where the reader comment noted at the top of the article and the comparison between BMW+Samsung batteries and Tesla+Panasonic batteries come in.
Long-Term Planning … It’s A Skill
Tesla+Panasonic batteries, it should be noted, have held up very well so far.
Also, remember that Tesla provides an 8-year and “infinite mile” warranty on its batteries.
Still, that doesn’t mean Tesla has the “best” EV batteries on the market.
The article recently linked by commenter Jenny Sommer was a 2013 interview with Sven Bauer, the CEO of BMZ, which at the time was Europe’s largest battery manufacturer (and perhaps still is, but I’m not seeing current data on this). Interestingly, he said “the battery life is not very long” for the 18650 batteries Tesla uses in its cars. He added that, “the cells in the BMW i3 are state of the art.” He said they are designed to last for 20 years.
First of all, I’m not sure how much he actually knew about Tesla’s batteries, since he indicated the battery cells were the same as those in laptops, but we know that Tesla’s battery cells are actually quite different from those, and Elon, JB, and team didn’t see conventional 18650 battery cells as adequate for cars either. But moving on from that….
The question is: Will Tesla’s batteries not be great for cars after 8 years? Will they last well enough to 20 years? Will BMW’s batteries really go to 20 years without losing comparable range? (Again, let’s also ignore how many batteries the BMW i3 has, even thought that’s important for the usability of the car, just to focus on the battery qualities themselves.)
These are questions none of us know definitively, but Sven seemed confident in his opinion. Asked how reliable the 20-year service life estimate for the BMW i3’s batteries is, Sven said, “It is very reliable. It is possible to prove this within exactly a month. Putting it precisely, the battery life is 20.9 years. End of life means that the battery can still be charged up to 80 percent of its original capacity.”
Again, after bouncing these comments off of Denis Rakcheev, he added more context:
Here there is an important aspect that was not touched by Mr. Sven Bauer. This is the design of the electrodes. High values of the energy density are defined by the specific area onto which lithium ions can get adsorbed. This specific area can be manipulated by, for example, adding more layers of the electrode material and/or by increasing the porosity of the electrode surface by arranging nanowire structures. Increasing the electrode-specific surface is an expensive process, that requires careful testing to ensure thermal stability and power characteristics of the cells. As a result, one gets a golden middle between energy density and power density. BMW took a cheaper way by using less-energy-dense cells. That’s why I think this comparison of ‘Goliath vs Achilles. Who’s weakness is bigger?’ starts to take shape when major details of the battery cells are compared.
Sven Bauer noted back in the 2013 interview that there was a price tradeoff for these longer-life batteries. He didn’t put out a price, but said that BMW’s battery cells cost more than Teslas. He stated:
“Large-volume cells with 20 years’ service life such as those in the BMW i3 offer significantly higher performance, but are currently more expensive in terms of watt-hours. Significantly less effort is required, however, for the battery management. We are now also talking about prices between 250 and 300 euros per kilowatt-hour, but for considerably higher performance and a longer life.” (Remember that this interview took place in 2013, so prices aurely are quite different today.)
In response to another question, Sven said, “Tesla has a battery that works. But in comparison with this, the battery in the BMW i3 is a quantum leap.”
Denis Rakcheev’s comment here was: “It is hard to believe Mr. Bauer, unless he can provide a comparison with Tesla on these three crucial parameters: price/kWh, kWh/kg, and kWh/m3. The lifetime of the battery slowly becomes the matter of management (thermal, 80% SoC, 80% DoD, peak consumption management) of the battery and less dependent on the chemistry of the lithium-ion cell (unless we are talking about different chemistries, such as lithium-air cells, liquid-flow cells, or some other exotic combination).”
Regarding Tesla’s batteries, Sven said that, using 18650 cells, “they are never going to achieve 20 years’ battery life…. If the battery is looked after carefully, perhaps eight years tops. If you regularly drive flat out or live in a hot region such as California, where the road can reach temperatures of 60, 70 degrees [Celsius], then perhaps only four or five years.”
I have to say, it seems odd that Tesla would warranty its batteries for 8 years and unlimited miles if “8 years tops” was actually the case and 4–5 years was more likely. With those claims, though, quotes from Sven are done. And [Edit: The preceding lines have been removed because I learned — or was reminded, since I must have read this before — that Tesla’s battery warranty does not cover degradation at all.] I’ll just reiterate again: it seems Sven was basing his comments on standard 18650 battery cells that are very different from Tesla’s battery cells. As Denis added, there are several other parameters to consider, and it seemed like Sven didn’t know what those were for Tesla’s batteries and made some odd assumptions.
I asked Tesla Motors a couple of times to look at the claims above and respond regarding expected Tesla battery lifetime (to 80% capacity), expected capacity after 10 years and after 20 years, and how it is that Tesla batteries are warranted for what this battery expert projected to be the top battery lifetime (to 80% capacity) for these battery packs. Unfortunately, all I got was a link to an article in the mainstream media that discussed Tesla Energy stationary storage products — nothing about the very different batteries used in Tesla’s cars — and there wasn’t really anything new (to me) or useful in that story anyway. [Edit: Tesla representatives also did not correct the assumption that Tesla’s EV battery warranty covers degradation to a certain point.]
So, we essentially have no detail from Tesla on these battery questions. What we know, though, is that Tesla’s warranty covers the battery capacity for 8 years
(that is, the capacity shouldn’t drop below 80% of the initial rating until after 8 years). Assuming Tesla didn’t choose 8 years with the expectation that many batteries would just barely last 8 years (that would be stupid), I expect most batteries should stay above 80% for at least a decade. [Edit: The preceding lines have been removed because I learned — or was reminded, since I must have read this before — that Tesla’s battery warranty does not cover degradation at all.]
Now, taking all of this into account, let’s come back to the question in the title: “BMW+Samsung Batteries vs Tesla+Panasonic Batteries — Which Are Better?”
Better is obviously a subjective term, but it is typically going to be evaluated based on a balance of cost, performance, and lifetime. It’s hard at this point to say BMW’s batteries offer the better value when Tesla has been able to take the #1 spot in the large luxury sedan market and BMW i3 sales are mediocre. Not even considering Tesla batteries’ higher power density, relatively high upfront costs are simply not loved by consumers, and consumers tend not to be very long-term thinkers with such purchases. Very few are thinking 20 years out when buying (or leasing!) a car.
That said, we don’t even know if the BMW i3’s batteries will really hold up for about twice as long as Tesla’s, and there’s the point hinted at above that a Tesla battery that drops from 250 miles of range to 200 miles of range (80%) is still much more useful than a BMW i3 battery that drops from 80 miles of range to 64 miles of range (80%), or even 72 miles of range (90%). I think I can predict which price would hold up better on the used car market.
Nonetheless, the matter is a very interesting one to me, and there are fundamentally interesting points to debate on how these companies should approach battery technology options.
We’ll have more perspective on these matters in several years when Tesla Model S and BMW i3 vehicles are a bit older, and when we have more news on BMW’s i5 and other electric car plans and offerings. Will BMW actually be able to offer something similar to the i5 Tom Moloughney envisions for a price that is competitive with the Tesla Model 3? Or is that too much to ask while BMW uses long-life but expensive Samsung SDI battery cells? Will Tesla’s batteries continue to hold up better than expected, or will their degradation leave consumers wanting an upgrade and suffering from degraded resale values in a few years? Will Tesla and BMW both stick with their initial battery decisions, or will one or both of them change course? These are all questions that I’m eager to see answered as time unfolds the future of electric cars and their battery hearts.
*I didn’t know where to slip this in, but here’s one more interesting comment from Denis: “Additional feature that contribute to the cost, performance and possibly to the life expectancy of the battery pack is how the pack electrically assembled. Tesla uses in the magnitude of thousands of 18650 cells, whereas the majority of others use commonly 96 or 192 cells. Each Tesla’s cell measures ~ 3,2 – 3,4 Ah, whereas the other use in the range between 60 to 94 Ah. In both of these approaches there are pros and cons. Tesla’s matrix style is more expensive to assemble, cheaper to replace a small cell, easier to control temperature on a cell level. The modular design of the others is pretty much the opposite of Tesla’s: cheaper to assemble, more expensive to replace a larger cell, and uneven or more expensive thermal control due to the lower diffusion speed into the bulk size of a bigger cell.”
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