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Tesla Charging for Maximal Li-Ion Battery Lifespan

Discussion in 'Charging and Infrastructure' 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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    • 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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      • MelindaV

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      • 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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