The black dots in the graph above are battery capacities for 44 German owned iMiev/CZero/iOns collected by datom. There is a link in his post above. The green curve is my model (Ah = 50.4 -1.14*ln(km)) for battery aging discussed in an earlier post. It looks like my car’s capacity deteriorated more rapidly during the first kms than was normal for the German cars. On the other hand, my present mileage is 80,000 km and my battery capacity is now average or above average.
I suggested based on my own data that the natural log model was probably the best description of battery aging, but the German data doesn’t support this conclusion. In fact it looks linear more than anything else.
Of the 44 cars 16 owners reported more than one capacity measurement. These are shown as lines in the graph below.
Some show a sharp decline in capacity early in the car’s life and others a slower decline in capacity later in the car’s life. However there is no statistical difference in the rate of decline between low mileage and high mileage cars. What is interesting is the wide range of the rates of decline. This may be due to variations in the manufacture of the battery cells but it could also indicate that there are things that we can do or avoid doing that will extend battery life.
In my case I bought my 2012 CZero in 2014 from a dealer. The car had no previous owner and less than 2000 km. Other than that, I don’t know how it was treated. When I first saw the car, it was in the dealer’s showroom with the charger connected. From 2000 km to 40,000 km we quick (Chademo) charged the car. Since 40,000km we have slow charged 70% of the time. I usually slow charge between the hours of 10 in the evening and 7 in the morning and the car isn’t charged up every day but on the average every second day.
Thanks to datom for the use of his data.