Does age of EV battery matters if it has low mileage?

Discussion in 'General' started by lwncmEV, Oct 11, 2019.

  1. lwncmEV

    lwncmEV New Member

    Hi everyone!
    A frequent reader but first time poster here. I have a question that I can't seem to find the answer to no matter how I Google it. Is the life of a liquid-cooled EV battery shortened by passage of time? I am in the market for a used EV that will last me for for a while. I found one that fits my range needs and is listed at a decently affordable price. The car is around 6 years old, but have low 5 digits mileage on it. I am talking about just breaking 10,000 miles. Should I be concern that the battery will give out in a few years? Please elaborate your point of view of why or why not. Links to scientific/industry/authoratative studies would be great in educating me on this! Your input most be most appreciated! Thank you!

    -lwncmev (low income but still would like to get into an EV.)
  2. What make are you looking at and manufacturing date? That would provide for information to base degradation. The thing to really watch for is out of warranty repairs to say the hydraulic brake controller, obc, A/C etc or many other electronic components. Try reading forum posts from other owners of the same make/ model/ year.
    interestedinEV likes this.
  3. lwncmEV

    lwncmEV New Member

    Hi electriceddy,
    It is a 2014 Ford Focus Electric. I did some look up. It is liquid cooled battery. So, how bad is the degradation of this 6 years old battery that is hardly driven?

  4. If it was a Leaf I could help you but this forum has 28,588 posts on the Ford Focus, so a better reference than I could give you:
    I used to post on the Leaf version of this forum and contained some very good topics:)
  5. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Unfortunately, you're not going to find a clear-cut answer to your question. Those of us who have read a lot about li-ion batteries know that they do have what is called a "calendar life", but nobody knows just how long that is. The oldest production EVs using li-ion batteries, the Gen I Tesla Roadster, made starting in 2008, are not yet showing any signs of battery capacity loss due to end of calendar life. However, different models of EVs use different battery cell chemistries, so different models may have different calendar life limits.

    But more or less all EV makers guarantee their battery packs against catastrophic failure for at least 8 years. Unless you're planning on keeping your car significantly longer than the average American, let's say past 11 years of age, then I wouldn't worry about it. On the other hand, don't expect the original battery pack to still be operating 20 years after manufacture. Maybe they will last that long, but I wouldn't count on it.

  6. lwncmEV

    lwncmEV New Member

    Thank you electriceddy. I will head on over to that FFE forum site!

  7. lwncmEV

    lwncmEV New Member

    Hi Pushmi-Pullyu,
    Unfortunately, 1) I am working with a very limited budget, and 2) I kept my current ICE car for 20 years. Let me go over to the forum electriceddy suggested and see what kind of longevity owners of the Focus EV has experienced. Thank you for your input!

  8. BlueKonaEV

    BlueKonaEV Well-Known Member

    I personally don't think that time will degrade battery too much if any.. I think that the biggest degradation comes from running the battery down too low and charging it up too high. If you purchase a short range EV, the chance that the battery has been run down to a very low SoC and charged up to 100% each time are very high. With a long range EV, most people can get through for most of the car's life by charging from like 65 to 80% every day. Keeping the SoC somewhere in that range will increase the batteries life. I saw some research by battery university where a Lithium/Polymer battery would still have 90% or so of it's original capacity after 4000 charging cycles if charging from 65 to 75% every day. If you can drive 300 miles on one charge, 4000 charging cycles would mean 1.2 Million miles before capacity drops below 90%. However, those are theoretical numbers as nobody will be able to charge from 65 to 75% every day for the life of the car. Every time you use the DC fast charger, you will take life of your battery.
    I'm personally usually at 50 to 70% SoC on most days at the end of the day and I charge to 80% except for road trips.
  9. I hope you get the answers you are looking for there and it works out positively for you.
  10. lwncmEV

    lwncmEV New Member

    Hi electriceddy,
    I got some suggestions to use a FORScan on that potential purchase. I will update on what readings I get off the FORScan.
    electriceddy likes this.
  11. DW'sGen2

    DW'sGen2 New Member

    I believe the life of the battery is measured in charge cycles, ie: how many times charged up to full, depleted, charged up, depleted.
    I think. Someone told me that and tied it to that's why it's better to charge only to 70% or 80% if possible, and to not run it too close to 0 if possible.
    So, that does not mean that time has no effect on battery longevity. But the guy who told me said it's all about the charge cycles.

    Sent from my SM-G955U using Inside EVs mobile app
    bwilson4web likes this.
  12. bwilson4web

    bwilson4web Well-Known Member Subscriber

    This YouTube does a good job of explaining the basic chemistry:

    • 8:32 / 10:37 - the SEI (Solid-Electrolyte Interphase) layer is described. This is key to LiON aging.
    Another, brief SEI video:

    A bit more technical, advanced research on using silicon instead of carbon anodes:

    The SEI layer is a harder problem when the anode materials grow and shrink by a factor of 2-6x.

    Bob Wilson
    Last edited: Oct 23, 2019
  13. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    There are two limitations: Cycle life and calendar life. It's unclear to me how much or how little those two are related. We haven't yet seen any end-of-calendar-life problems in production EVs. But the OP was asking about calendar life, not cycle life.

    Cycling results in fairly gentle, usually steady loss of capacity over miles driven. (Nissan Leaf battery packs, with their lack of liquid cooling, appear to be somewhat more erratic in how fast they age.) End of calendar life is supposed to be very different; a sudden drop off a cliff. As I said, we haven't seen any reports of that happening... yet. We will some day.

  14. lwncmEV

    lwncmEV New Member

    Hi all,
    Here is the status update. I never got to plug in the OBD adaptor and ran FORScan. The car was sold before I got there. :(
    Thank you for all your insight and assistance in helping me understand better!

  15. bwilson4web

    bwilson4web Well-Known Member Subscriber

    Patience, another will be coming by-and-by.

    Bob Wilson

Share This Page