Tesla Charging for Maximal Li-Ion Battery Lifespan

Discussion in 'Charging, Infrastructure & Efficiency' started by Brokedoc, Sep 2, 2017.

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  1. Brokedoc

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    I've heard many different views on battery charging methods to improve lifespan so I just wanted to put out my new charging parameters and rationale.

    My facts: My daily commute is usually under 50 miles. I have a 75kw battery. Based on the range indicator when fully charged, 100% battery charge give me about 225-230 miles. 90% charge is about 205-210 miles, 80% is about 175-180 miles. Tesla's manual recommends leaving vehicle plugged in when not in use to allow the battery management system to keep the vehicle around the preset charge level and extend battery life.

    My new charging settings as of tonight: I will set my battery charge level to 70% and charge at 15 amps overnight. A 50 mile depletion in the battery will take about 4-5 hours to charge at that rate.

    My rationale for the 15 amp charge rate (this rate can be adjusted on the car's screen): Too low of a charge rate is not maximizing charging circuit efficiency to overcome resistance in the system (I believe a previous thread determined less than 12 amps was the threshold for efficient charging). Faster charging rates is not needed for my daily commute miles and generates additional heat which can further degrade battery lifespan. For those that have a longer commute, you can adjust this charge rate based on your mileage and number of overnight hours and also whether your utility has cheaper rates during specific hours.

    My rationale for the 70% overnight charge level: #1 Elon, #2 Jeff Dahn, leading battery expert and leader of Tesla's battery research partnership with Dalhousie University. See recent Electrek article. Apparently, Li-ion battery lifespan decreases when the battery is repeatedly discharged below 20% and also when it is repeatedly charged to 100% (no wonder my cell phone battery dies so quickly!). Optimizing battery life, according to the experts, seems to occur when the battery cycles around the 50% point. My preset charge level of 70% overnight charge will result in my daily commute battery cycle between 50 to 70% but still allow me reserve if I make additional trips during the day.

    For roadtrips, I will still charge to 100% and use the supercharging stations, but these will be minimal.
     
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  2. Brokedoc

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    As an addendum to my original post, I am also reducing my Supercharging and I would avoid other forms of DC fast charging such as CHADeMo. There are times that supercharging is convenient and unavoidable such as on road trips but it has recently become clear that the ultra fast charge rates adversely affect the battery chemistry and may shorten lifespan of the battery pack.

    There is a VERY lengthy thread on another user site about Tesla throttling the Supercharger rate after the vehicle has reached a certain number of DC fast charges. My summary of this thread is that the battery chemistry deteriorates after repeated fast charging and Tesla's throttling algorithm only decreases the charge rate by a few percentage points. This may be something to keep in mind when buying a used Tesla...

    Full Thread here on Tesla throttling Supercharger charge rates.
     
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  3. MelindaV

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  4. Model34mePlease

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    One feature that I don't think Tesla has, but the Plug-In Prius that I used to own did, is the ability to stop charging at a particular TIME. This would be in addition to stopping at a particular level of charge.

    Those of us that have time-of-use billing would like that as a check to going over the time limit and getting socked with high kWh prices. It will usually be the case that this is unneeded because a decent 240V charging system will reach my desired charge level well before the rates go up, but if I arrive home late and have little charge left, I don't really want to have to recalculate the stopping charge level to prevent going over the time limit.
     
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  5. Insaneoctane

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    I think you're on track. For some, they say set to 80% or even 90% and never worry about it again. That mentality probably works for leasers or people that upgrade cars often. I'm neither of those AND I happen to have a long daily commute (110 miles round-trip) . Therefore I worry about this more than the average owner. For starters, calculate your daily commute as a percentage of the 100% SOC battery range. For me, that's 35% (110 mi / 310 mi). Divide this in half, 17.5% (35% / 2). Add this to 50%. For me, 50% + 17.5% = 67.5%. So, for my daily commute, charging to 67.5% is ideal for battery longevity. Next, you apply the common sense and convenience factors. This math leaves me with 32.5% at the end of my commute for "pop ups". Everyone's lifestyle is different, some may have unpredictable things constantly. For me, having 32.5% is perfectly adequate for most pop ups and a supercharger fixes it if I'm wrong. I will round up to 70% SOC. If I know I need more mileage any particular day, I can up the SOC. Don't forget climate can significantly impact these calculations, so winter might easily drive up your SOC target. Good luck and happy charging
     
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  6. Dan Detweiler

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    This is virtually exactly what I will be doing and for all the same reasons. Glad to know I'm not the only one thinking this way!

    Dan
     
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  7. BellevueEd

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    It seems like the concept of charging to 100% doesn't necessarily make much sense for leaving on road trips. The charge level should be determined by the distance to the first Supercharger station, so 70% may well turn out to be a good cap, with a margin for error, depending.
     
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  8. reallove

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    I am a bit confused about this and several other threads regarding charging. My confusion comes from what it appears to me is a contradiction between the model 3's official manual and everything the experts are saying, including EMusk.
    The manual states the following:

    "The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model 3 for several weeks. When plugged in, Model 3 wakes up when needed to automatically maintain a charge level that maximizes the lifetime of the Battery."
    (caps and bold original in the manual)

    Wouldn't Tesla mention anything about charging to 70-80% levels if that were to maximize the lifetime of the battery?
     
  9. Brokedoc

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    Tesla officially labels the "Daily Trip" range on the charge settings between 50%-90% and labels the 100% rate as road trip.

    The battery management system for Tesla is much more advanced than the ones in cell phone chargers and does not float/trickle charge. Once it reaches the preset level, it stops charging and once it drops to a certain point, it will restart charging.

    For extended storage, I would suggest setting the charge level at 50 or 60% and allow the car to do the rest. If you are returning from a prolonged trip, you can adjust the charge level in your app when you're on the way home to your usual charge level of 70% or 80% or whatever.

    If anyone has a Tesla Powerwall, can you comment about charge settings? I'm not sure if those charge levels are adjustable or if Tesla presets a max of 90% so that it doesn't get to 100% on a sunny day and stay there for hours....that would degrade the Powerwall very quickly.
     
  10. garsh

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    Yes, it's curious that the manual makes no mention of why someone would choose to change the charge level.

    I also checked the S owners manual and it's no different in this regard.
     

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