Battery Degradation Over Time

[SageBrush2]

I came across a database from 'Plug-in America'
https://survey.pluginamerica.org/leaf/results.php

that is comprehensive in its data gathering and has some 600 entries, although most of them are for 2011 - 2013 MY cars. Their data analysis report is informative but they set the independent variable to miles driven. I was more interested in battery degradation as a function of battery age and manufacture year. Few people reported Gid or SoH values so I relied on capacity bars. I also rather coarsely determined battery age as the year of the reporting entry less the year of manufacture.

Results

• Although not exact, I find it useful to think of decimals of capacity bars in terms of fractions of owners between two levels. So e.g. if a result is 10.33 I read it as 1/3 or the group has 11 bars and 2/3 of the group has 10 bars

• The data confirms the general impression that battery quality improved through the years, particularly for the 2013 MY compared to earlier MY

• Some of these sub-groups are small, so some flexibility in identifying trends is called for.

• The 7th year data for the 2013 MY is only two cars and is distorted by my LEAF which still has 11 bars

Edit: png resized
PM me for the Google Doc, or just grab the CSV or JSON file from the website. The raw data is identical and has not been modified in any way.