All cars drop in value as they get older, become worn, and have travelled further. Electric vehicles have the added consideration of declining battery ‘State of Health’ (SoH). This is a measure of how much charge the battery can hold compared to when it was first manufactured, so a brand new car will have 100% SoH. SoH determines how far the car can go between charges, and time before you’ll have to do a battery make-over, and it is likely to affect the resale value of your car – so it’s best you check it out before buying.
We recommend that you get a copy of a recent scan of the battery before purchasing or settling the price. Most dealers will scan the batteries and show the results if you ask, but otherwise get someone from your local EV Owners group to assist, or you can do it yourself by following the instructions at http://flipthefleet.org/resources/nissan-owners-how-to-scan-your-battery/. You can then compare your prospective purchase against the tables and graphs below that show the latest statistics from the Flip the Fleet database.
The first section compares SoH versus year of manufacture; the second section compares total distance travelled (odometer reading) versus year of manufacture; and the last section shows a scatter graph of SoH versus odometer reading.
Battery State of Health versus year of manufacture
Nissan Leaf SoH is measured by LeafSpy (upper) and dashboard ‘bars’ (lower) for cars. The graphs show the percentiles: 50% is the middle of the pack (half have a higher SoH and half lower); 5% of the EVs have a SoH less than the 5th percentile, and 95% above it.
Be aware that the top (twelfth) bar on the Leaf’s battery health display (extreme right of the dashboard) is worth more than the bars below it i.e. the 12th bar drops off when the SoH drops to around 85% (80% for the 30kWh variant of the Leaf). Thereafter each remaining bar drops off about equally, and each is worth about 6.25% of charge holding capacity. Therefore a 10-bar Leaf is likely to have a SoH somewhere between 72.5 and 78.75% SoH.
The data presented in this post were for the January 2018 data upload cycle i.e. as reported in the first few days of February 2018 – but we also used some historical data if a vehicle didn’t have its SoH reading added for January 2018.
Below the graphs we present the percentile estimates as numbers for more accurate benchmarking and the table shows the raw scores. N is the sample size for each year and model. Beware of placing too much reliance on the percentiles where sample size is still small.
If you buy an EV, please sign up at www.flipthefleet.org and contribute your data for the people following you: this is a “By EV owners, for future EV owners” approach.
Most commentators advise that the age of the car (year of manufacture) has a much stronger effect on SoH than distance travelled.
Odometer versus year of manufacture
Most commentators advise that odometer reading itself is a less important determinant of an EV’s value and condition than for an Internal Combustion Vehicle (ICV). This is because EVs wear more slowly and cost less to maintain. Flip the Fleet will soon be able to test the relative importance of odometer reading and year of manufacture on an EV’s condition and value, but we don’t yet have enough data to do that reliably. In the meantime you can compare the odometer reading of a prospective purchase against other New Zealand Leafs of the same year and model using the table below.
Battery SoH versus odometer
Lastly we present a scatter graph of the SoH versus odometer of the EVs of different year and model. You can see the wide scatter in the graph – obviously lots of other things than just age of the EV and odometer affect battery health. Flip the Fleet needs more data to test ideas about what causes this variation and to see how best to minimise battery SoH loss.
Henrik Moller, Daniel Myall and Dima Ivanov
27 February 2018.