Tesla Batteries Retain Over 90 Percent Charging Power After 160,000 Miles, Survey Finds (engadget.com)

According to a survey of over 350 Tesla owners, Tesla batteries retain over 90 percent of their charging power after 160,000 miles. The EVs dropped only 5 percent of their capacity after 50,000 miles, but lose it at a much slower rate after that. Most Tesla vehicles will have over 90 percent of their charging power after around 185,000 miles, and 80 percent capacity after 500,000. Engadget reports: Tesla has no battery degradation warranty on its Model S and X luxury EVs, but guarantees that the Model 3 will retain 70 percent battery capacity after 120,000 miles (long-range battery) and 100,000 miles (shorter-range battery). That's a bit more generous than the one Nissan offers on the Leaf (66 percent over 100,000 miles) for instance. According to the survey data, Tesla will easily be able to meet this mark.

Comments

Re:Too expensive

[Mr D from 63]

This 'survery' was basically a collection of message board posts. 350 respondents, but the article doesn't say how respondents reported results with so many miles. I looked at the first few pages of respondents and none reported having driven near 100K miles yet. So I assume the actual sample of high mileage owners was quite small. Too bad the author neglected that obviously important info.

OK, here is the actual data if anyone is interested;

https://docs.google.com/spread...

Re:Tesla Batteries

[Rei]

Indeed. A few other things:

  * For a vehicle with a range of, say, 250 miles, where the driver drives, say, 25 miles per day, is only using 1/10th of a cycle per day.
  * Few owners charge to 100% daily. Most set a limit in the 60-90% range, with 70% and 80% being common. So not only are they doing shallow cycles, but they're doing shallow cycles in a near-optimal-for-longevity portion of the pack.
  * Unlike laptop batteries, which are often just cells in series and thus limited by the weakest cell, Tesla packs have many dozen cells in parallel forming bricks, which are then linked in series (these in turn are linked in parallel). A failure in an individual cell has an insignificant impact on the whole.

In short, you have shallow cycles, in a gentle portion of the charge curve, with a chemistry specifically designed for long life, a failure-resistant architecture, and climate controlled to optimal operating conditions. You get what you design for. A cell phone and a laptop, by contrast, design for low unit cost and high energy density. Tesla packs are only 150-180Wh/kg, whereas you might get over 240Wh/kg in a cell phone battery. But cell phones and laptops are only designing for a couple year lifespan, with deeper cycles every day, no redundancy, no climate control, etc

Re:Too expensive

[dgatwood]

Those use pretty much the same kind of batteries, donâ(TM)t they? You might not get 500k miles out of them on a bike, but in terms of capacity after x charge/discharge cycles they might well be similar.

I doubt you would even get close, realistically, for two reasons:

• Tesla vehicles use a heat pump to keep the battery within a narrow operating temperature range to minimize battery degradation during both regenerative braking and normal charging.
• Tesla vehicles contain additional pack balancing circuitry to ensure that each cell gets charged as much as possible even if it is surrounded by weaker cells, and to ensure that cells can discharge as much as possible before the pack fails.

A bicycle is not likely to do either of those things. It probably isn't even physically possible to usefully put a heat pump into something the size of a bicycle—a motorcycle, maybe, but not a bicycle.

Re:How are their batteries so much better than lap

[Rei]

1) Laptop batteries are designed for energy density, not longevity. There are tradeoffs in chemistry selection.
2) They're not climate controlled. Just the opposite, they're right next to a source of heat.
3) They go through deeper cycles, over a wider portion of the SoC range.
4) They have no redundancy / cell bypass
5) They're designed for a product with a pre-determined expected lifespan of only a few years, so they have no incentive to do better.

You can design to any spec, if you're willing to accept the tradeoffs.

Re:Self selected survey, no reason to trust it

[dgatwood]

Tesla batteries have an eight year warranty. Tell us another one.

Temperature controlled

[burtosis]

Tesla batteries last in part because of the advanced temperature control. They are kept warm in the winter, and cooled when you are flooring it, hot lithium batteries don't last long and cold ones don't perform well till they warm up. That's why the leaf is bad in some situations as a very cold or hot pack hurts performance and lifetime accordingly. A second strategy is to not fully charge or discharge them, using only a fraction of the battery pack capacity. This also extends life quite a bit and is used by virtually all electric car manufacturers. Here is a good article on a particular cell the tesla uses. Tesla, like several others, use cells that are more robust to abuse with a long life at the expense of actual capacity at high discharge rates, but it's a good tradeoff price wise even though the cells are more expansive. Not covered here is the long term stability of the cells as not a function of cycles but one of cycles and time. Just like any battery they age even if not used. You may get a whopping 35 thousand charges if you go from 80% to 20% capacity but that's not the case if you wait 10 years and store the battery properly. So take this article with a grain of salt because it does not have an actual time component other than couple of years it takes to get the data. These cells haven't been around 20 years so one needs to extrapolate and guess as to the actual long term viability.

Re:Musk's dilemma....

[whoever57]

I saw one article (I can't find it now -- perhaps it has been pulled), that attempted to compare ICE cars and Tesla cars, specifically the Model 3. It claimed that the Model 3 had a big drawback that would have to buy a new battery in 20 years time. Guess what you call most ICE cars when they are 20 years old? Mostly: recycled metal and other materials. The basis for the new battery claim ignored published data on the life of batteries, choosing instead to substitute some numbers the author had pulled out of one of his orifices.

The article also chose to arbitrarily increase the cost of batteries from what they are today, instead of assuming that battery prices would continue to drop.

I am convinced that some big short sellers are paying for a disinformation campaign, to force Tesla stock down.

Re:Musk's dilemma....

[Rei]

Apparently you stopped reading before "the short selling thesis is fatally flawed because of numerous wrong assumptions"

Re:Musk's dilemma....

[Rei]

Nah, the shorts will first try to claim it's a burst rate. After a few weeks they'll start switching their attacks to "Tesla can't be profitable." Once Tesla turns a profit they'll switch it to "It's a one-time thing, but doom is just around the corner. DOOOOM!!!"