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Updated: August 23, 2017. Tesla Motors provides an 8-year infinite mile battery failure warranty but it doesn’t cover degradation. Therefore it is highly relevant for every Tesla driver to know what to expect of the degradation of the capacity over time, because it is equivalent to the range of your car. In the Netherlands, Merijn Coumans is updating on a regular basis, via the Dutch-Belgium Tesla Forum, a file of owners’ data, created by Matteo. The most recent (Aug 23, 2017) version of the results is displayed below. Detailed explanations are also in the google doc file, as well as at the end of this blogpost. The new files also have data input possibilities for USA and other non-km (i.e. miles) drivers.
In the figure the percentage of range loss is shown on the vertical axis. The horizontal axis displays the distance (in km) driven with the vehicles.
The red fitted line has a slope above 60.000 km (say 40,000 miles) of 1% per 50.000 km (30,000 miles). On average the batteries have 92% remaining at 240.000 km (150,000 miles). If the linear behavior would continue, then the ‘lifetime’ (still 80% capacity left) can be calculated as follows: 92-80 = 12% times 50.000 km = 600.000 km, plus 240.000 km, gives 840.000 km (500,000 miles)! Note that a ICE car has a average lifetime of 220.000 km (140,000 miles)… And remember: if an ICE fails after say 300.000 km, you have a problem. The battery in a Tesla EV after the suggested 840.000 km (ok, lets take 500.000 km, still great!) still has 80% capacity left!
To put in into perspective, on a 0-100% scale, it looks like this:
Here is a nice video introducing an interactive graph from Teslanomics
The way to measure this is to do a full charge (100%) and then check the EPA rated range (in North America) or Typical range (in Europe and Asia/Pacific). In the plot, these numbers are then compared to the range numbers the car displayed when it was new. For example, for the 85 kWh Model S85 variant, this is about 400 km typical range or 265 mi EPA rated range. Even though this is mostly a reliable method, sometimes the computer in the car can’t accurately estimate how much energy the battery holds and might display an inaccurate range number. To improve accuracy, it is a good idea to run down the battery to almost empty and then charge to 100%, once a month. This is known as rebalancing the battery. However, the battery shouldn’t be left at 0% or 100% for more than 2 hours.
Besides Mileage vs Remaining Range, the file includes two other charts: Charge Cycles vs Remaining Range and Battery Age vs Remaining Range. From literature and research we know typically that 80% of battery capacity remains after 1000-2000 full cycles, strongly dependent on the temperature of the batteries. The data below support these numbers.
Here is a recent update from the USA with almost 130000 miles driven as max.
From the USA+ drivers I could find the following previous data of the Plug in America Survey, and used it to generate the following picture:
I compared all provided data with the EPA 265 miles number for the 85kWh Model S and to the 210 miles EPA number for the 60 kWh models. It is not clear of course how trustworthy this data is, and how peoples measured..
If you like the km version, here it is:
Links on battery degradation:
Here is a very nice report on the Tesla Roadster by Plug-in America, one result is the following one, based on 126 vehicles:
here are some of the notes supporting the data at the top of this blogpost:
|◘ These charts are updated every time there is a new entry. All charts on this page show entries from all locations.|
|◘ The trendlines are generated by the chart. Hover over the trendline to see the current formula.|
|◘ When range mode is on, the displayed range in the car increases a few miles or km. For all calculations, this chart uses range numbers with range mode on because this statement by Jerome Guillen: “EPA testing is [done] with range mode on, given that it is assumed customers will use that function when they want to drive the farthest.” In other words, because the range scores are achieved with range mode on, it is more accurate to do calculations based on range numbers when range mode is on. But users don’t have to turn on range mode just to read their 100% charged range. The chart will calculate that accurately.|
|A video showing how range mode effects displayed range||Youtube|
|◘ A cycle is when multiple percentage charges add up to 100%. For example charging 5 times from 70% to 90% is 1 cycle. Professor Jeff Dahn who is an expert on Tesla batteries said the following when responding to a question by a Tesla owner:|
|Quote: “If you charge from 30% to 70% 150 times or from 10% to 70% 100 times, the ageing of the battery will be approximately the same”.||Source|
|A video of Prof Dahn comparing Model S battery to other EVs||Youtube|
|◘ If you don’t see your name on cycles chart, go back to data entry and enter lifetime average energy consumption (Wh/km or Wh/mi).|
|If you have a replacement battery, don’t be surprised if you don’t recognise the mileage and battery age numbers you see above. These numbers are calculated for your replacement battery. They are different than your car mileage or vehicle age. If you want to know more about how this calculation is done, read on. Otherwise this might be too much detail.
Let’s assume somebody entered this data:
|Mileage calculation for replacement battery: If the battery hadn’t been replaced, typical range would be 390-5= 385 km on the old battery at 30,000 km.
If 30,000 km equals to 400-385 km range loss
then X km equals to 400-390 km range loss
Cross multiply. X= 30,000 * (400-390) / (400-385) = 30,000 * 10 / 15 = 20,000 km. The chart will display 20,000 km
|◘ Why does the chart display 20,000 km even though actual mileage on the replacement battery is only 30,000-24,000= 6,000 km?
Because this replacement battery was refurbished and had some mileage on it.
◘ Why does the chart display 20,000 km even though mileage on the car is 30,000 km?
Because the chart displays mileage on the current battery not on the car and it has calculated that the replacement battery has 20,000 km mileage on it.
◘ How would the chart calculate age on the replacement battery?
Age = 350 * (400-390) / (400-385) = 350 * 10 / 15 = 233 days
|◘ What mileage would the chart show if the replacement battery still had 400 km range?
Even though the calculation would result in zero miles (X= 30,000 * (400-400) / (400-395) = 30,000 * 0 / 5 = 0 km) the chart recognises that the calculation shouldn’t be less than what the user reported. In this case odometer shows 30,000, replacement happened at 24,000. Therefore mileage on the replacement battery is at least 6,000 km. Therefore the chart would display 6,000 km. The age calculation for the replacement battery would result in zero days too because the typical range is still 400 km (same as a new battery). Of course zero days would be incorrect too because the battery has 6000 km on it. Again the chart wouldn’t use zero and would calculate the time that corresponds to 6000 km mileage as follows:
If 30,000 km equals to 350 days
Then 6,000 km equals to X days
X= 6,000*350/30,000= 70 days
|◘ 30 July 2015: The Mileage Chart now switches between km and miles depending on location of selected username. We have now more entries from USA than before. So I thought this would be useful. Matteo|
|◘ 11 Feb 2016: The trendline for the first chart (Mileage vs Remaining range chart) has been updated. The old trendline was a third order polynomial trendline. It worked fine for 0-120,000 km where there are lots of entries but after there were no more entries it showed a sharp drop. The new trendline is polynomial until the data ends but linear afterwards. Like the old trendline this new trendline is also calculated automatically by the chart and updates when there are new entries. Matteo|
|◘ 9 Aug 2016: I added a script that clears the username selection in E1 every 2 hours. Matteo|