Batteries

Published on May 31st, 2016 | by Christopher Arcus

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Battery Lifetime: How Long Can Electric Vehicle Batteries Last?

May 31st, 2016 by  

Electric vehicle have become a common sight on streets today, and many people have started to enjoy the quiet comfort, getting used to charging at night and silently doing errands.

BMW-i3-Dark-Grey-Kyle-Field

Photo of a BMW i3 at an EV charging station in California, by Kyle Field for CleanTechnica.

Electric vehicles are new enough to wonder, how long will they last? This is not a simple question, because it depends on chemistries, sizes, operating conditions, and pack configurations.

Most electric vehicle batteries are lithium based. When a lithium battery is charged and discharged once, it is called a cycle. Lithium battery capacity degrades as the cycle number increases. Battery cycle life is measured in cycles, with an industry standard of cycles to 80% capacity often used as a benchmark. What makes lithium batteries last a long time? Let’s turn that upside down. What shortens lithium battery life?

  1. High temperatures.
  2. Overcharging or high voltage.
  3. Deep discharges or low voltage.
  4. High discharges or charge current.

Overcharging at high temperatures — what does that mean? When a lithium battery is charged, its voltage goes up slowly. When it reaches full charge, battery voltage is highest, and will not go up much more. The max voltage (V) varies with lithium cell chemistry. Chemistries ranging from laptop batteries to power tools using lithium-cobalt blends and blends containing manganese, nickel, and aluminum have terminal voltages around 3.9 to 4.2V. Lithium-titanate batteries charge to 2.85V. Lithium-iron-phosphate batteries charge to about 3.65V.

Lithium battery voltage must be prevented from exceeding this voltage because it not only ruins battery life; it can lead to battery destruction or overheating and fire in some lithium batteries. Battery management systems (BMS) are used to control charging voltage so that the max charging voltage and temperature is never exceeded.

High voltage also leads to another limit, called calendar life. When foreign matter builds up, it prevents the flow of ions at the electrodes. Lithium-ion batteries contain electrodes, conductors through which current enters or leaves the cell. In between the electrodes is an electrolyte, a solution used to conduct current between the cells. Conduction is achieved through exchange of ions between electrodes and through the electrolyte. The chemical interaction within the battery is called a redox reaction.

When a lithium-bearing electrolyte comes in contact with the electrode, it forms a layer. The interface where the exchange of ions happens between the electrode and electrolyte is called the solid electrolyte interface (SEI) and this forms an SEI layer.

Buildup of material blocks the flow of ions at the SEI layer at the end of calendar life.

sei

The SEI layer contributes to internal resistance. As the battery ages, the layer increases and internal resistance increases. At some point, the layer becomes large enough that no ions can pass and the battery life ends. This kind of battery lifetime limit is worsened the longer the cell is kept at maximum voltage and high temperature. The idea here is to avoid maximum voltage and high temperatures for extended periods of time. Battery manufacturers are aware of this, and keep their batteries at states of charge of as low as 40% to maintain battery capacity during storage and shipment.

To increase cell calendar life, overvoltage and high temperatures must be avoided.

At the other end of cell voltage and charge, for maximum cycle life, deep discharge must be avoided.

The charge level in batteries is described in two ways. One description is called state of charge (SoC). If a cell is fully charged, it is said to be at 100% SoC. The other description is depth of discharge (DoD). If a cell is fully discharged, it is said to be at 100% DoD. That means a 100% SoC cell is the same as 0% DoD. SoC works like a fuel gauge.

For maximum battery cycle life, 100% DoD must be avoided. Researchers have found that improvements in cycle life increase non-linearly as depth of discharge is reduced.

“The data suggest an inverse power-law dependence of the cycle life on the DoD, such that a four-fold lifetime gain is
achieved going from 100% to 50% DoD,” DeVries, Nguyen, and Op Het Veld write.

Here is a Cycle Life versus Depth of Discharge curve:

Cycle Life vs Depth of Discharge

Cycle life improves faster than DoD reduces, so that the total charge transferred is greater at lower depth of discharge.

This is significant, because it means that a larger battery used at less than full discharge can be more economic and last longer than a smaller capacity battery used at full depth of discharge.

If a battery pack is designed to have capacity providing long range, it is likely that daily charging will be at low depth of discharge. The impact of this on electric vehicle design is important. It means that the route to long range, high capacity, may also result in lower depth of discharge and longer life for a given battery chemistry. Further, if maximum charging is intentionally limited during most operation, battery calendar life may be extended.

Finally, batteries are characterized by C rates. Simply put, a battery will be specified in amp-hours. An amp-hour is the amount of current the battery can pull in one hour.

The C rate is defined in units of C, where 1C means the battery can be charged in one hour. If the battery is charged at 2C, it means the battery may be charged in half an hour. High-C-rate batteries can be charged or discharged very fast and produce a lot of power. Low-C-rate batteries have lower power.

For lithium batteries of a given chemistry type, modifications can be made to raise or lower C. The tradeoff is higher energy capacity in kWh for lower C, or power. In a battery pack, more cells in parallel lower the peak current in each cell and allow each cell to operate at a lower C rate. In an electric vehicle application, the desired peak battery pack current can be reached with either a pack with more parallel cells (thus, larger energy capacity) or fewer parallel cells and a higher C rate. With parallel cells, a low-C battery can stay within its C limit.

The impact of this on electric vehicles is that a battery pack sized for long range can have lower C rate and higher energy capacity.

Exceeding C rates results in anode changes that degrade performance. Proper electrode operation depends on the electrode surface structure. That structure is changed if the C rate is exceeded.

A number of benefits appear when an electric vehicle battery is sized for long range. A larger-capacity battery results in a lower average depth of discharge and consequently longer cycle life and lower peak charge/discharge rate. If maximum charge is limited to 80% under everyday driving conditions, maximum voltage is avoided. If the battery pack is also thermally controlled, both maximum voltage and high temperatures are avoided. In this way, controlled conditions can increase battery life substantially.

Properly designed, an electric vehicle with large capacity battery may be designed to control conditions affecting battery life and result in a long-range vehicle with long battery life.

We now have real-world evidence that controlling conditions in this way can result in long battery life. The Tesla Roadster achieves long battery life with lithium-cobalt batteries by controlling all four of the factors listed: temperature, maximum voltage or full charge, minimum voltage or depth of discharge, and C rate. A cursory analysis of electric vehicle mileage based on 100% discharge cycles yields an erroneous result because it does not consider the effect of reduced depth of discharge. With a range of over 200 miles, and an average daily mileage of about 30 miles, cycle life and mileage is extended. Daily charge defaults to 80% charge, limiting maximum voltage and extending calendar life. Calendar life increases by controlling pack temperature and limiting maximum charge to a short period of time because trips are taken soon after full charge. C rates are reduced and controlled because the pack current capability is large relative to charge and discharge rate. All those controlled conditions contribute to longer battery life and mileage.

Tesla Roadster

Tesla Roadster by Tesla Motors.

From the article linked above:

“Obviously, nobody knows exactly how long Tesla packs will last. The math is somewhat simple, though. The full capacity of a lithium-ion battery cell should be good for 300 to 500 cycles. So if you drive a Roadster through 300 194-mile standard-mode cycles, it translates to 58,200 miles. If it’s 500 cycles, how does 97,000 miles on one set of batteries sound? 

“Of course, as Battery University explains, it’s not as simple as that. After 300 to 500 cycles at 100 percent depth of discharge, a lithium-ion cell’s capacity will drop to 70 percent. But partial discharge “reduces stress and prolongs battery life.” Drain the batteries consistently to only 50 percent, as is often the case with electric cars that get plugged in frequently, and life expectancy of a healthy battery zooms up to 1,200 to 1,500 cycles. That, of course, translates to 366,000 miles, but don’t expect numbers like that on your odometer. Other wild cards such as frequency of fast recharge can also affect battery life.”

With better characteristics of NCA cells used in the Model S, even greater battery life performance may be possible.

Tesla Model S

CleanTechnica Tesla Model S reviewer Kyle Field snapped this photo of a Model S P90DL in Santa Barbara, with Kyle’s Model S and a new blue Model S in the background. How far will each of these Teslas drive?

Other manufacturers are continuing to increase electric Vehicle range and battery performance and life. Chevy has announced the Bolt with 200 miles of range, while both Nissan and BMW have let it be known they also intend to increase range.

BMW i3 protonic blue 1

2017 BMW i3 by BMW

2015 Tokyo Motor Show

Nissan IDS Concept by Nissan

Operating conditions can have a dramatic effect on battery performance and lifetime. Battery life must be assessed from both operating conditions and battery characteristics to accurately determine results. If you see claims from outsiders about the cycle life of a company’s batteries, be sure to find out if they have correct assumptions regarding temperature, maximum voltage or full charge, minimum voltage or depth of discharge, and C rate.





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About the Author

has studied wind, electric vehicles, and environmental issues. An electrical engineer familiar with power and electronics, he has participated in the Automotive X Prize contest. He is an avid writer, specializing in electric vehicles, batteries, and wind energy.



  • OneHundredbyFifty

    Couple of questions that are unclear to me:

    1) What level of degradation is assumed in the graph. In other words, it says you get close to 8000 charge discharge cycles if you do 10% DOD. After that point is the battery able to hold 50% of rated charge, 30% of rated charge, 70% of rated charge. What is the criteria.
    2) What is the data source for the graph? I don’t see it in the cited articles.

  • namyzarc

    Alot of the comments regarding 100% vs 80% charging are missing an important point:
    The degradation of a 100% charge only applies if that charge is held for a long period of time. If You charge to 100% then use that charge immediately, then degradation becomes a non-issue.
    With the Nissan Leaf for example, you can set the time when you wish the battery to complete it’s charging. So if you normally leave for work at 7am, you can have the charge complete at 6:30 for example….

    • eveee

      Thats what this article says.

  • My main strategy for being kind to the battery of my Zoe is not charging her after I get home, but charging her before I leave.

  • onesecond

    In Germany a Tesla Roadster owner drove 200000 km and the capacitiy dropped to 70% by then, this was already in 2012.
    I remember a story from a Model S owner in the US that already drove 200000 km with his car by 2015, but no battery degradation was mentioned.

  • Matt

    Go watch the Jeff Dahn video 5 stories down. It puts a lot more science behind it that this story.

  • Nick Flynn

    I think the cycle life of batteries designed for EV’s should be much higher than 500 cycles even at a higher voltage charging. The excellent video titled “Why do Li-ion Batteries die ?” recently linked at clean technica goes into much more detail. 500 cycles is a good standard for cheaper laptop consumer devices cell. I’d expect auto manufactureres to do a lot better than that.

    • nakedChimp

      What is ‘higher voltage charging’ ?

      One daily cycle at 80% DOD (starting with 100% each day) and you get 2,200 cycles means a life expectancy of the battery of 6 years.
      And the battery still has got 80% of the range when it was new.

      You might want to align your wrong expectations with reality there.

      • Nick Flynn

        “What is is higher voltage charging?”

        Charging to 4.2 volt as opposed to 4.1 volts or less. Many manufacturers charge to a lower voltage to increase the cycle life at the expensive of range.

        I agree you can get decent cycle life out of cheap consumer batteries by charging to 80% DOD but I’d expect car batteries to be quite a lot better, although we won’t know for sure until they’ve been around a few years.

        I’d seriously recommend you do a search for “why do li-ion batteries die and how to improve the situation” The presentation has lots of interesting statistics from the study of real automotive batteries. Real data is much more interesting with arguing with unknown people on the internet about who is right.

  • I think this is overly technical for most, a general user needs to know that their battery will last the life of the car (10 years or 150k miles) or so. Plug it in and drive, don’t worry about underlying tech.

    With a few exceptions like early Leaf models, battery degradation has been very small. Several Volt cars have 100k EV miles with no battery degradation at 4 to years and 2500 charge cycles (60% DoD).

    A buyer who wants to drive to 150k miles should maybe plan on the range being 60-80% of new range though, as a typical EV run at 85% or 95% DoD will have more range loss than a Volt, but at the same time the battery isn’t charged near as often, a Bolt EV might only have 500 charge cycles to go 100,000 EV miles vs the 2500 for the Volt.

  • JamesWimberley

    As with solar panels, the critical question for consumers isn’t how long the batteries will last, it’s how long they are warrantied for. It would be reasonable for long warranties to be subject to correct use conditions, with only exceptional deep discharges, etc.

    • Agreed. There is unnecessary confusion with capacity warranties being separate to the Materials and workmanship warranty.

      Nissan began with no capacity warranty, relented when their customers sued them and now have different capacity warranties for different size batteries.

      In addition the dealers are typically uneducated as to the fact the capacity isn’t warranted along with the rest of the car and/or extended warranties purchased.

  • vensonata .

    Excellent article. Keep as a reference source.

  • Leeper

    I have a 12 mile daily commute and a Mitsubishi imiev. With my range I can get around 4-6 trips depending on variables. Is is better on the battery to let the soc get down to 2/16 bars or to just plug in every night after only using a couple bars?

    • AaronD12

      I’m not sure people know with the i-MiEV’s battery chemistry. The i-MiEV’s battery has been quite resilient compared with others like the LEAF. When I had my i-MiEV, my commute was the identical length to yours. I still charged (almost) every night and slept well knowing that if the car didn’t charge, or the power went off, I could still make it to work.

      • Benjamin Nead

        I found the material data safety sheet for the LEV50, which is the 50Ah prismatic cell used in the i-MiEV pack (88 of them total.) It’s Lithium Manganese Dioxide chemistry . . .

        ww.ens.dk/sites/ens.dk/files/klima-co2/transport/elbiler/forsoegsordning-elbiler/praktiske-erfaringer-elbiler/erfaringer-citroen/Batteri – trillingbiler.pdf

        It also appears from reading this that Mitsubishi sets the charging voltage per cell at just below 4.1V (the nominal operating voltage per cell 3.75V) So, that’s a pretty low charging voltage number, which is good if you’re concerned about long cell life.

        I also spent about 1+ hour this evening watching the Jeff Dahn video found here . . .

        http://cleantechnica.com/2016/05/30/lithium-ion-battery-expert-jeff-dahn-start-tesla-motors/

        It a fairly technical presentation (for me at least) but there were a few things I could immediately take away upon a single viewing.

        One was that experiments in multiple additives in the electrolyte can have radically different results on the life of the cell. So, one can assume that both Nissan’s and Mitsubishi’s improved cells from 2012 (the “Lizard” and LEV50N respectively) probably came about from this sort of tweaking, even if the chemical composition of the cathode remained the same.

        Another is that heat is bad for batteries (already knew that) but it’s the time that it spends in the heat charging (longer is worse,) charging to 100% capacity every time and letting the car sit for a long time like that in high heat is also something to avoid.

        So, the hot summer regime I came up with the other day of charging to around 80% most nights, when it’s coolest, is about the best I expect to do.

    • vensonata .

      I think the Miev is lithium titanate. In that case the cycle life is 10 thousand cycles…ridiculously long lived. They don’t have the energy density, of lifepo but they can be rapid charged without much degradation. An interesting trade off. The battery may well outlast the car. But it would be interesting to get feed back from IMiev owners.

      • sault

        The i Miev only got the SCiB titanate batteries in the Japanese model. The USA just gets regular li-ion batteries:

        https://en.wikipedia.org/wiki/Mitsubishi_i-MiEV#Battery

        Bummer…

        • Benjamin Nead

          Correct. The Toshiba SCiB LTO battery pack is Japan-only.
          With a CHAdeMO charger on just about every street corner in every Japanese city (check out the PlugShare app,) you can perpetually quick charge 4 or 5 times a day if you need to really get around. If I had my druthers, I’d have 2 iMiEVs:
          a “long range” lithium ion one for the cooler weather and an LTO one for the murderously hot summer desert days.

          But the conventional lithium ion cells found in all other i-MiEVs and all the Euro Citroen and Peugeot variants are the very durable, iif somewhat non-sexy, Yuasa/Bosch prismatic LEV 50 series. More robust and longer life than what’s in the Leaf? Yeah, probably. We’ll know for sure in another 7 to 10 years.

          There’s a good article here that details the difference between the earlier LEV50 and improved LEV50N cells, and what’s different with the smaller capacity packs found in the Euro badged cars . . .

          http://pushevs.com/2015/11/04/gs-yuasas-improved-cells-lev50-vs-lev50n/

          If you want to go into information overload on i-MiEV battery info, the excellent My i-MiEV Forum has all you would ever want to know. Here’s the first page of the battery tech thread directory . . .

          http://myimiev.com/forum/viewforum.php?f=23

      • eveee

        Yup. They need high cycle life in the iMieV. The thing has one of the smallest packs (16kwhr?) of any EV. But LiT is a wonderful battery for longevity if you treat it right.

    • sault

      If you can automatically shut off charging at 80% SOC, then just charge it every night. Long charging sessions increase the amount of time the battery is hot from charging, so charging up once every 4 days or so subjects the batteries to higher temperatures for longer vs. charging every day. Plus, look back at the lifecycle curves in this article. Discharging only to 20% DOD allows for almost 8000 cycles in the test battery (the red line). Going down to 80% DOD brings cycle life down to 2200 cycles. In your case, you should go from 20% DOD every morning (charging to 80% SOC max) and run it down to 30% – 35% DOD during your daily commute. As an added bonus, when extra errands unexpectedly pop up, you’ll have the range for them and you won’t drain your battery to as high a DOD.

    • eveee

      Dont discharge it fully. That will lower cycle life. Charge every night, but not to 100% unless you drive away immediately. Here are the things to avoid:

      1. 100% discharge. Better to charge every night.
      2. Full charge for long periods. Charge up fully for long trips the night before and drive away the next day. For daily commutes that are shorter, try charging to only 80% if you can manage it.
      3. Temperature. If your car has battery thermal management, you are in luck. If not, keep it away from high temperatures.

    • Benjamin Nead

      First, very good detailed battery tech article here. Lots to reference back to.

      I’ve now had my used 2012 i-MiEV for a little over 6 months and have
      put just over 2700 miles on it . . . light work commuting (6 mile round trips,
      5 days most weeks) and typical urban errand running for the most part. Mix in a little out-of-the-way joy cruising (the little car’s CD sound system is surprisingly good and I now carry a rotating collection of around 10 discs in the glove compartment,) so the 400 mile monthly average has recently skewed upwards to 450 miles – including a 60 mile round trip one day (charging mid trip) I took in early April, midtown Tucson to Biosphere 2 . . .

      http://i.imgur.com/x5pQkTH.jpg

      I’d guess that 98% of my charging has been done at home, almost always at night, and every last bit of it, so far, has been done at 120V. I have a 2014-16 vintage stock EVSE that allows me to toggle between 12A and
      8A current draw (the stock 2012 unit is 8A only) and I invariably choose
      12A. At that rate, an almost completely empty battery will charge in about 13 hours. But I try not to deplete the pack to that extreme regularly. 9 hour overnight charges at 12A are more typical.

      For those that don’t know, the i-MIEV has 16 graduated bars on it’s battery gauge (the Leaf has 12.) But gauge doesn’t feel linear once it gets near the bottom. Once you’re at 4 bars to go. those bars disappear pretty quickly.
      Once you’re down to 2 bars, the display starts flashing. At a single flashing bar, I’ve been told I have 10 miles to go before the car enters “turtle mode” – super slow top speed that might take you another 6 miles or so – but I’ve never tried that.

      Mitsubishi actually recommends once a month to let the car get down to 1 or 2 flashing bars and then let it completely charge to full (the EVSE’s charge light flashes to let you know you’ve gotten there,) to fully balance the cells in the pack. More typically, I’ll run it down to around 20% capacity
      (4 bars) and then back to full or near full. I might do this 3 times a week.

      With very hot southwest desert weather now looming (it was in the low 90s F today, but will be approaching 109° for several day by the end of this week,) I’m going to start not charging to full, but do an approximately 20%
      to 80% charging regime around 5 nights a week.

      Because the i-MiEVs stock instrumentation is really bare bones, a couple of folks have stepped up to develop Android-based apps to thoroughly analyze battery pack performance and other parameters. All you need is an Android tablet (Google Nexus 7 here) and a bluetooth OBD2 reader. Then, these 2 apps with tell you oodles . . .

      https://play.google.com/store/apps/details?id=emobility.canion&hl=en

      http://www.evpositive.com/evbatmon-for-i-miev.html

      Note that the latter app is also going to have an iOS version soon.
      Only scratching the surface with this stuff, but these 2 programs have already told me I have a pack that is exceptionally healthy.

      The i-MiEV comes with a somewhat primitive remote that allows you to set
      charging duration (basically an electronic timer timer and nothing to properly dial in charging percentages,) so the aftermarket has come to the rescue here as well. This gadget from Juice Box will give you good precision charging control with smart phone connectivity on any existing J1772 EVSE . . .

      https://www.emotorwerks.com/index.php/store-juicebox-ev-charging-stations/online-store/1631-juiceplug-a-universal-smart-ev-charging-adapter/category_pathway-23

      But I’m probably going to spring for this all-in-one unit later this summer and also now give myself the 240V L2 charging option . . .

      https://www.emotorwerks.com/index.php/store-juicebox-ev-charging-stations/online-store/1661-juicecord-pro-20-portable-smart-20-amp-evse-with-20-foot-cable/category_pathway-23

  • john

    This is a good explanation of the use or abuse of batteries, however the most important aspect is the software that ensures that a user does not use a vehicle that will result in having a detrimental effect on the expected battery life of the pack.
    Because EV’s are a totally different bread of energy source to the ICE vehicle it is going to take some time until consumers understand the ramifications of ignoring the warnings shown on their information displays saying YOU MUST CHARGE NOW.
    I think most of the people who have an Electric Vehicles are techno literate and understand the requirements to gain the best use of the product.
    To me the most important aspect is to ensure that the software is written to ensure that the average person is looked after.

    • ADW

      Agree: Part of the issue I worry about is many people claiming EC are “maintenance free” when in fact the proper charge/discharge is like having your oil changes, transmission, timing belt, and clutch rolled into a single point of failure. We have 100 years of driving until the fuel light comes on, now we are being asked to charge at 50%. Its a big mental change.

      Software and a well designed User Interface are critical in this working once EV makes it to main stream. On my current ICE the check Oil light is a now orange “Oil at 10% of life: Change Oil” that does not go away until I change the oil.

      For an EV there is going to be a need for education on ‘best practices” for a long battery life. We will no longer have the ‘scheduled maintenance programs’, we have to have a ‘drive this way to avoid long term issues’.

      • sault

        “Idiot-proofing” the vehicle software is a must. In a perfect world, EVs would automatically stop charging when they hit 80% SOC or whatever optimum number is for it’s particular chemistry. Drivers would have to “opt in” to bring that up to 100% on the days they actually need the range. The problem is that Nissan got schwacked on the EPAs range rating for the LEAF when they included 80% charging as an option, so this is why we can’t have nice things apparently.

        Wireless charging is looking to be the next big thing, so hopefully it will eliminate the problem of drivers forgetting to plug in every night and even get rid of the plug format wars (Chademo vs CCS vs Tesla SC) if a DC version can be designed.

        But for now, driver behavior is the weakest link in maximizing battery life.

        • eveee

          Yes. Tesla has that feature for normal everyday charging. They have a setting for long range that allows one to charge to 100%. The short amount of time at 100% won’t hurt range much.

          All EVs and chargers should have features like that.

          Most EVers won’t forget to charge over night. Its about like putting the phone back on the hook. It can be a habit that is easy and quick. But auto companies could add a reminder beeper connected to the car or smartphone, so you might have a good idea there.

        • The Mercedes B and Toyota RAV4 already have the opt-in feature.

          • Nissan LEAF had that feature in the 2011/12 models. They removed the feature when the EPA started to measure the vehicle range based on an 80% charge. The EPA argued that Nissan recommended drivers charge to 80% so they set the range calculations based on that starting in 2013.

          • eveee

            Yes , that was unfortunate. But I believe you can still set things back to 80% charging, its just not the default anymore. Do you have any info on that?

        • nakedChimp

          Wireless charging without format wars?
          Are you kidding?

          That charger protocol wont match that car.
          That frequency wont match that other type.
          Those antenna forms wont work well with those receivers.
          etc pp.

          Every idiot out there is trying to make it as proprietary as humanly possible to stake out a market with high entry barriers for competition.
          Why?
          Profits.
          Interest payments and shareholder value as high and for as long as possible.
          Why?
          Look no further than your monopoly legal tender.

          • OneHundredbyFifty

            RS-232, USB, Bluetooth, WIFI – Companies can arrive at standards when they need to. They fight the rest of the time but when their is a compelling reason they come together.

      • eveee

        A meter reading might help, you think?

      • neroden

        If you drive until the fuel light comes on, you’re an idiot! I was always taught to check the fuel gauge and refuel when it was at 1/4.

        Made for an easy transition to an electric car…

    • eveee

      Yes. Tesla has set their cars up to only charge to 80% SoC. Thats a big benefit to lifetime. That and thermal management. Many other things are buries and inaccessible to the user, so we don’t know specifics.

    • Ashraf Hassan

      Question on heating and cooling technology 1) Does the Tesla Model S use the “heat pump” technology for heating and cooling the cabin or battery, using the invention patented #US 428057 A by Nikola Tesla in 1887 for a Pyromagnetic electric generator? 2) Does Tesla plan on making an in-car magneto-electric refrigerator using this same patent? google com/patents/US428057 3) Does Tesla plan on making use of the Nikola Tesla 1888 & 1901 A/C induction “stepping motor/reluctance engine” now being used by Audi as an electric “forced induction” supercharger? Normally to be used in gas hybrids. blog caranddriver com/going-electric-the-next-phase-in-forced-induction/ More on ICE vs A/C & Dieselgate nikolateslasolar blogspot com/2015/09/dieselgate-volkswagen-vw-diesel html

      • john

        I do not know the answers.
        However the tesla owners club or tesla may have those answers

        • Ashraf Hassan

          Is the Ford Motor Company’s patent in 1971 for an “A/C reluctance engine”, actually Nikola Tesla’s “stepping motor”, and also the same as the A/C motor in the Tesla Model S? google com/patents/US3560820

        • john

          There is a new post on this site about the shareholders meeting and there is mention of the AC propulsion aspect
          note 6 and 7
          http://cleantechnica.com/2016/05/31/tesla-shareholder-meeting-notes/

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