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 Post subject: Charge to 80 or 90?
PostPosted: Fri Jun 14, 2019 3:44 pm 
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Joined: Sun Apr 21, 2019 12:27 am
Posts: 12
We've been charging our new '19 car to 80% using a level 2 charger and the "minimum charge" trick. But I've been reading various stories that VW already has a buffer built-in where the car is really charging to something like 90% even when full. If that's true, should we set the min charge to 90 to approximate the "optimal" 80% SOC?


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 Post subject: Re: Charge to 80 or 90?
PostPosted: Fri Jun 14, 2019 4:09 pm 
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Joined: Sat Dec 19, 2015 4:16 pm
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Truly "optimal" is closer to 60% but the car is pretty useless then. I'd do 80 unless you need the range.

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 Post subject: Re: Charge to 80 or 90?
PostPosted: Fri Jun 14, 2019 4:27 pm 
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Joined: Fri Jan 23, 2015 1:18 pm
Posts: 457
True, there is buffer. Where a Tesla (supposedly), let's you charge each cell to 4.2V, on the e-Golf 35.8 kWh pack, the 100% SoC voltage is 4.1 V. If you read the scientific literature that looks at cell cycling and degradation rate, by charging to 3.9 V instead of 4.2 V, the cycle life of the cell is increased by about 10 times before showing the same amount of degradation (~5000 cycles vs ~500 cycles), and these studies usually look at full battery cycling from the max chosen SoC to a very low SoC like 5% or 10%. You will also get increased cell life if you keep the lower end to 20% or better most of the time. Of course, if you only charge up to 3.8 V, there is a further fold increase in cycle life, and yet more cycle life at 3.7 V. But as was already mentioned, what are you willing to live with on a daily basis? 80% is 3.94 volts, by my measurements, so I charge to 80% routinely and am comfortably able to get 80-90 miles of range and still have about 30% SoC left.

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 Post subject: Re: Charge to 80 or 90?
PostPosted: Fri Jun 14, 2019 11:00 pm 
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Joined: Sun Apr 21, 2019 12:27 am
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Thx for the clarification. 80 it is then.


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