Bolt EV: Battery Degradation at 70,000 Miles
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DC Fast Charge Effects on Battery Life and Performance Study
Vehicle Battery Testing - Fast Charging Effects
Wow...70k already!?
Suppose all those DCFC sessions on your Bolt is more than likely the reason why.
DCFC has been proven to degrade capacity sooner than those who charge exclusively on L1/L2 at least as tested on the Leaf linked abvoe...
Long story short, under consistent maximum use of battery and high current chargers over long term (2 yeas and 70,000 miles) he lost 6% of battery capacity. Barring more extreme use than that, you could do better to far better. Sounds like degradation not an issue for most people if you use/charge intelligently.
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I use Hilltop Reserve to mimic the Volts buffer zone. I use L2 charging. I would use DCFC on the rare, very long trips I take if DCFC were generally available in my area. That availability will increase over time.
Fixed it for you, eliminating the unintentional value judgement.
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That is not bad degradation. I am interested to see if degradation slows time with miles.
I'm going to start using Hilltop Reserve Mode consistently now (I almost never used it for the first year--always charging to 100%). That should reduce battery degradation significantly moving forward.
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Thanks for the report, you're a pioneer for all of us and I for one highly appreciate all the info you've been sending our way. Keep up the great work!
But not what I meant. By intelligently I meant not charging to the extremes every time just because you can. Not a value judgement but known idiosyncrasies of the lithium ion battery.
Thanks!
In some ways I agree. In other ways I disagree. What is "known" to you is not known to the general population. That's not an issue of intelligence; it's an issue of ignorance. My channel (and why I do what I do) is primarily educational. One of the most common questions people have about EVs is long-term reliability, and I'm presenting an extreme use case and discussing how others can minimize degradation.
So, eventually, yes, people will be able to charge more "intelligently." However, in the meantime, they first need to be presented with the information so that charging intelligently is an option.
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I haven't noticed any degradation and now have 81k miles, but that's just anecdotal rather than hard numbers/charts - I use hilltop reserve probably 99% of the time, and have used DCFC probably only 10 times max. I wondered if routine use of DCFC would be to long-term HVB life and performance, but if OP has measured the degradation to 8% that's pretty darn minimal IMHO.
While one would think high amp charging would have a detrimental effect, it seems it has little effect and the biggest hit is 0 to 100% charging (serious degrading in as little as 500 charges according to chart posted in another post). The other surprise from the same chart is the increase in number of charges as the charging is brought back from the extremes. I'll never complain about the upper and lower buffer zones again (OK, I never actually did).
Can you please expand on the Hilltop Reserve Mode? We are starting to research Bolts and would be happy to learn more.
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This thread is super important info, thanks for starting it.
I think that a good day to day operational SOC range is between 20%-90% SOC
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It's a setting you can turn on that prevents the Bolt from completely charging the battery. It's meant for those that live on top of a hill, so they can regen power to the battery while going down the hill, filling up the battery on the downhill drive.
It's also being used by some to simulate the the way the Volt prevents total battery charge/discharge by keeping an unused buffer, thereby helping extend battery life. So don't totally recharge the battery, don't totally drain it either. You could simply unplug the car before it finished the last 10% or so, but that requires timing. With Hilltop Reserve, the car stops charging early automatically.
Keep in mind, all batteries will degrade over time. So the OP's car may have degraded by maybe 4% or 5% (a guess) instead of 8% had he not been been fully charging and not using DC fast charging so often.
Hey, Jeff. I think you're one of the Bolt EV owners I was thinking of when wanting to "compare" battery degradation. Now that I hear your use case, I'm even more interested in seeing the difference. I have no doubt your degradation is significantly worse than mine, despite having a few thousand more miles.
I did a pretty basic breakdown of it here:
I drove a Leaf for 3.3 years before getting my 2013 Volt. Phoenix, AZ.
There was a period of about 5 months when I had to drive the car pretty hard to get to the far end of the city (about 120% of what the car was capable of then. I ended up doing a lot of DCFC on a hot battery in the summer. I was traveling every day of every weekend. LeafSpy indicated the battery temperature rose to >140F (air was >90F), and tended to stay there as wasn't time to allow for cooling.
At just under 2.7 years/ 33k miles, my Leaf battery had lost 30% of its capacity, enough to qualify for a battery replacement covered by warranty. I had a new car again.
Deep cycles and DCFC take their toll. At least the Bolt/Volt have battery cooling support to mitigate the heating problem.
6% loss over 70k miles/2 years and many DCFC? That's doing very well in my book.
There was a period of about 5 months when I had to drive the car pretty hard to get to the far end of the city (about 120% of what the car was capable of then. I ended up doing a lot of DCFC on a hot battery in the summer. I was traveling every day of every weekend. LeafSpy indicated the battery temperature rose to >140F (air was >90F), and tended to stay there as wasn't time to allow for cooling.
At just under 2.7 years/ 33k miles, my Leaf battery had lost 30% of its capacity, enough to qualify for a battery replacement covered by warranty. I had a new car again.
Deep cycles and DCFC take their toll. At least the Bolt/Volt have battery cooling support to mitigate the heating problem.
6% loss over 70k miles/2 years and many DCFC? That's doing very well in my book.
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Another reason to lease a Leaf, yes. Another reason to buy EV's with active liquid cooling for the battery and avoid those with air-cooled batteries. Another reason to recognize that frequent DCFC use does have an effect on battery, even if small it can add up over time.
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Wow. Great idea. That would remove battery anxiety.
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