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New Nifty tool! - Best practices for battery charge level for long battery life

Discussion in 'Model 3' started by Khan3, Sep 3, 2017.

  1. Khan3

    Khan3 Member

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    Been following a number of threads on TMC related to best practices for charging your Tesla EV (mostly for model S and X, but would similarly apply to model 3).

    Most of the key questions have been like :

    a) Should I charge daily or every couple days?
    b) What should i set the maximum charge level to? 90%? 70%? 50% ? ... etc
    c) How low can i deplete the battery without significant long term degradation of the battery?
    d) Should I connect the wall connector even if i really don't need a charge?
    e) Is it better to charge in small bits many times, or just wait and do big charges?

    Mostly along those lines.

    So I decided to do some research, and found a deluge of information, lots of opinions, but not much in the way of actionable intelligence. Like most engineering problems, there is no simple one-answer-fits-all answer. The correct answer requires proper context. In my research i identified the following key factors impacting long term battery performance a) temperature of battery b) State-of-charge (SoC) or level of battery charge c) Depth of discharge (DoD) ... how much of battery capacity you use d) Charging voltage

    Luckily Tesla has taken care of a) Battery Temparature - by actively managing the temperature/condition of the battery. They also handle d) via the on-board charging electronics.

    So the one area left to Tesla owners are b) SoC and c) DoD

    Optimal practices for managing these are directly related to the owners daily range requirement. So depending on how many miles you need out of your EV daily there is an 'optimal' setting you should be using to achieve the best long term battery life. I've put links to the research that underpins this (on tool page), but also have created a tool where you can specify your specific context and get a recommendation for what the best settings for you are.

    Have a look and all feedback is welcome!

    model3guru.com / optimal-charging
    model3guru.com/optimal-charging

    optimal-charging.png
     
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  2. C141medic

    C141medic Member

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    Bookmarked already. Thanks again for another useful tool. How about putting all these nifty tools into an app?
     
  3. Zoomit

    Zoomit Member

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  4. SlicedBr3ad

    SlicedBr3ad Member

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    Thank you! This tool really drove the point home about how often I would have to charge and it's DAILY even though daily commute is just 65 miles while using base m3. Until now, I was silly enough to think I'd be charging it every couple of days.
     
  5. SocalEV

    SocalEV Member

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    Here is an interesting video on this subject. Looks like 70% charge level is best for day to day charging. Come from a very reputable source.

     
  6. SlicedBr3ad

    SlicedBr3ad Member

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    If you read comments, it's possible the battery used for recommendation was different in chemistry from Tesla and is not a good recommendation. However, charging max to 70, 75, or 80 % will only be relevant waaaaaay down the road if at all.
     
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  7. Zoomit

    Zoomit Member

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    Don't overthink it. You should be able to drive at least 2 days without anxiety and without any harm to the battery.
     
  8. SocalEV

    SocalEV Member

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    All batteries regardless of chemistry have similar characteristics. When electrons get tightly packed in a small space they cause friction(like a large family at a Christmas dinner table ;)), friction causes heat. Heat is bad......period. Since I plan on keeping the car for many years to come and my daily commute is less than 50 miles per day. LR at 70% would be more than enough. If there is a even a remote possibility that higher charge depth can reduce battery life, then I wont take a chance? Specially when I won't don't need to. At one time I was thinking of leasing the car, I would have not even thought twice about it and charged to 100% everyday.
     
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  9. gregd

    gregd Active Member

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    Ok, so 70%, plus or minus.

    Next question: How fast should you charge to get there, assuming you have the time. Charge as fast as your plug will go, or back it down?

    Not counting efficiency effects on the cost to charge (higher current generates more waste heat), is it better for the battery to charge at, say, 24 amps / 240 volts, or 48 amps / 240 volts? I seem to recall that he said faster is better (less time spent heating the battery), but that was regarding supercharging. I wonder if that statement holds for non-supercharging too?
     
  10. Khan3

    Khan3 Member

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    Thanks for all the great feedback!

    @C141medic - I do plan to put all these tools into an easy to use app that model3 owners can keep closeby. Lookout for this towards end of the year around when deliveries should ramp up and we have a lot more reference data to support the tools.

    @Zoomit , thanks for the charger list, i'll update mine to match - what page did you find that image on?

    Per the video relating to the learned Prof's response, I did review it as part of my research and find it totally consistent with what I found. The professor provided a simple answer to the simple question posed, given that the question had no context for the driving range requirements or context. If you look at the research link, they found that the battery life is maximized when used in the 65 - 75% range (i included diagram below - the yellow band). So it's totally consistent for the response to the question to be "keep it at about 70%" .... HOWEVER ... that answer will definitely change if your daily range need is 120 or 140 miles a day ( in which case your daily DoD will significantly do more damage than raising your charge to 80%).

    Given the opportunity for a more robust discussion i bet the Professor would respond along the same lines.

    battery-optimal-bands.png
    source : https://www.researchgate.net/publication/303890624_Modeling_of_Lithium-Ion_Battery_Degradation_for_Cell_Life_Assessment
     
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  11. Khan3

    Khan3 Member

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    @gregd - i didn't come across any articles that identified correlations of charging current/voltage/speed impact on battery degradation.
    I'll keep a lookout and update once I see something ... interested to know myself.
     
  12. Canuck

    Canuck Well-Known Member

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    Even more than daily, according to Tesla: "An important and simple way to preserve the life of the battery is to always leave the Model S plugged in while at rest." This is what I got with my vehicle:

    A connected Model S is a happy Model S

    It makes since short shallow discharges make lithium ions batteries last longer.

    Yes. I didn't watch the video but I did point out that according to the science there is no ideal charging percentage for everyone since according to the science you want to cycle around 50% and everyone drives different percentages daily...

    Jeff Dahn's recommendation on long term battery preservation
     
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  13. Zoomit

    Zoomit Member

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    see this post: New UMC
     
  14. SmartElectric

    SmartElectric Active Member

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    Set slider to 90%.
    Plug car in whenever you can.
    Relax.

    Our 2013 S has 97%+ of original range and we charge 90% daily, and 100% every weekend. We do not baby the battery. 4 years and counting. Tesla says to plug in, so just do that. Anyone doing more than this is overthinking and adding no value to the battery.
     
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  15. insaneoctane

    insaneoctane Member

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    Great tool and thread. While many folks are okay with the punchline of charge limit to 90% or 80% and forget it, others (usually the engineering type) thirst for more information and you've helped supply that! I tend to do a lot of research of front, only to end up setting my SOC at the lowest % that is comfortable. I will likely buy the LR to help avoid battery issues since I drive a lot and plan to keep my model 3 for a LONG time (10 years). Interestingly enough, your graph doesn't support the need for this decision, because even with a round trip of 110 miles daily, on the SR I would be on the cyan line (3rd from the top). With the LR, I move up one line to the purple one, not a significant savings at all! This is a little harsh because I'm using this to justify the LR ;) I will likely stay with the LR due to flexibility...thanks again for the tool.

    FEEDBACK/ SUGGESTED CHANGES:
    These would benefit me, so maybe others?
    • My suggestion is to show somewhere the "extra" range left at both your MIID-POINT and upon return HOME..
      • This is why I think that information is useful....for SR, If I drive 110 miles round trip daily, if I choose the tool's advice of 75% SOC, then when I arrive at my destination (110 mi/2 =55 miles later) what range is left to 0%? Also when I arrive home (110 miles later), at 25% SOC, what is my range to 0%? This would allow me to see the flexibility with your suggested settings. If I leave home with SOC @ 75% and arrive at my destination with SOC @ 50% my range is 110 miles. Therefore, if I get a call at work and have to go somewhere, I have 110 miles or range remaining. Also, if I just come home, my SOC is @ 25%, which means I now have 55 miles on range to go to dinner, meet my brother, etc. Simple math for your tool, and helpful for planning and deciding if the recommendations fit your needs.
    • It might also be helpful to let the user change the max SOC setting. (ie. BEST = 90% retention @ 9K cycles, BETTER = 90% retention @ 5K cycles, GOOD = 90% retention @ 3K cycles, OK = 90% retention @ 2K cycles, etc)
      • Then you could play with different settings that give you your desired range at destination and/or home to match the flexibility you desire? This is probably only useful if you add my first suggestion
      • Can you turn the cycle numbers into months/years based off the round trip mileage? If you could, you'd likely have to have another setting for average per month or number of days per week? My round trip is 110 miles daily, but I only do it 4 days per week and occasionally 5 days, so my 110 miles round trip is like 4.2 times per week....
    Just my thoughts....
     
  16. diplomat33

    diplomat33 Member

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    On week days, I only do about 10 miles of driving per day. So I am thinking I can probably go a few days in between charging. It seems silly to plug in every night if I have only driven the car a few miles.
     
  17. Khan3

    Khan3 Member

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    @insaneoctane thanks for the great feedback! Will definitely add information to show what the full range would be for the given max SoC so that users can have an idea how much headroom/flexibility they have.

    @diplomat33 , remember that plugging in serves two purposes:
    a) recharge the battery
    b) provide power for cooling/warming battery to maintain optimum battery temperature

    Depending on where you live (if garage very cold or hot), you will be wasting battery cycles if you don't plug in as the car will use its own battery power to condition the battery temperature
     
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  18. SmartElectric

    SmartElectric Active Member

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    Pro tip (after 4 years of driving two EV's and not pumping any gas):

    Plug in. Get in the habit. It's good to start every day with 90%, for those rare times you need to drive 300 km the next morning and didn't plan for it.

    I plug my phone in every night too.
     
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  19. SmartElectric

    SmartElectric Active Member

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    Engineering type here. Plug in and forget it works, and I am highly analytical. I've found that Tesla's recommendation of 90% and a plugged in car is a happy car is exactly right.

    I also have zero degradation on my Smart ED, and it's tiny battery is drained half way daily and charged to 100% (no other option) nightly.
     
  20. diplomat33

    diplomat33 Member

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    Thanks. Your advice makes perfect sense. I am in the habit of always plugging in my phone every night even on days when my phone's battery is still at 80% at the end of the day. That way, I always start every day with a phone at 100%, ready for whatever I might need it for. Makes sense to do the same with my Model 3.
     

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