Charging Habits and Battery Health

[sub]

I babied my Tesla's battery for the first year. Aside from an occasional road trip, I never charged more than 70% or let it drop below 50%.

After that year my degradation was slightly worse than average based on Teslafi stats.

At that point I decided there was no need to continue babying the battery and have charge to 90% every day. Now at year 5, I am slightly better than average.

I don't doubt that hanging out at 50% is slightly better for battery longevity, but I no longer believe that the impact is particularly significant. Other factors that you can't control probably have as much or bigger impact than your decision of whether to charge to 60, 70, 80, or 90%.

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[SANZC02]

I babied my Tesla's battery for the first year. Aside from an occasional road trip, I never charged more than 70% or let it drop below 50%.

After that year my degradation was slightly worse than average based on Teslafi stats.

At that point I decided there was no need to continue babying the battery and have charge to 90% every day. Now at year 5, I am slightly better than average.

I don't doubt that hanging out at 50% is slightly better for battery longevity, but I no longer believe that the impact is particularly significant. Other factors that you can't control probably have as much or bigger impact than your decision of whether to charge too 60, 70, 80, or 90%.

From my experience with my Model S most of my degradation was in the first 2 years, probably 4% of the 7% I noticed. Last 2 years has been pretty flat.

 

[zefram47]

This guy seems pretty smart and seems to say you should do frequent small charges if possible. I’ll let you decide how much stock to put in to YouTubers recommendations.

It's not the recommendation of a YouTuber, it's actually based on research from Dr. Jeff Dahn who works with Li Ion batteries. Engineering Explained just condensed the information down to something more easily consumed, but he linked an hour long talk by Dr. Dahn and a couple journal articles.



Profile of Dr. Dahn
https://www.dal.ca/diff/dahn/people/jeff_dahn.html

Research paper from 2021, Royal Society of Chemistry.
https://pubs.rsc.org/en/content/articlehtml/2021/cp/d1cp00359c

Research paper from 2014 in the Journal of Power Sources.
https://www.sciencedirect.com/science/article/abs/pii/S0378775313016510

 

[Eric9610]

I thought I saw a very large study that tracked thousands of EV's and charging habits that stated the outcome is the same no matter the setup.

Here is the link 12,500 Tesla's in study and not statistical affect on battery when comparing slow charge to constant DC charging.
Link

It sounds like the most important thing is preconditioning the battery to prevent derogation.

 

[SeaGeo]

You're battery charging routine is ideal.

Minor nitpick, this data only shows the lowest max charge down to 75%. It doesn't keeping between say... 40 and 60%. Really nitpicking, but it's only ideal relative to the charging cycles tested in that chart.

 

[shrink]

It's not the recommendation of a YouTuber, it's actually based on research from Dr. Jeff Dahn who works with Li Ion batteries. Engineering Explained just condensed the information down to something more easily consumed, but he linked an hour long talk by Dr. Dahn and a couple journal articles.



Profile of Dr. Dahn
https://www.dal.ca/diff/dahn/people/jeff_dahn.html

Research paper from 2021, Royal Society of Chemistry.
https://pubs.rsc.org/en/content/articlehtml/2021/cp/d1cp00359c

Research paper from 2014 in the Journal of Power Sources.
https://www.sciencedirect.com/science/article/abs/pii/S0378775313016510

Thanks for sharing the abstracts! Those were pretty technical and dense (and I do have a doctorate albeit in a completely unrelated field)

The YouTuber, backed by scientific data , literally says, “Don’t wait to recharge” and that smaller recharge cycles are better than deeper recharge cycles.

I’ve been driving EV’s since 2011 and have always been advised to plug in as often as possible and that shallow recharge cycles are better. I have seen recently many people not plugging in regularly and waiting to recharge. I don’t see the benefit to that and I’m not sure from where such practices originated.

If an an electrical engineer can tell me otherwise, I’m happy to listen and learn.

In the meantime, I’ll keep plugging in whenever not in use and limit SOC to 70%.

Again, open to learning if I should be doing otherwise, but I’ve been at this a while and have never heard of any benefit to waiting to recharge (other than when trying to balance and calibrate, but I’m not an engineer).

 

[Fmc]

Always
Be
Charging
Daily

who knows if it matters but my understanding is depth of discharge helps, therefore more frequent smaller charges should help battery life. Also it helps for impromptu road trips. Lastly there is an 8 year warranty on the battery, therefore it is Rivian’s problem for the first 8 years.
Enjoy the ride.

 

[Yinzer]

I had a thought about charging last week. Generally I keep my battery level between 20%-70%. My daily commute uses 10% each way. I charge at work bringing the level back to 70% and when I return home in the evening I charge again returning the level to 70%. The thought I had was maybe this daily charging is not the best practice and I pondered the idea that it might be better for the battery packs if I ran them closer to 20% and then charged returning them to 70%.

I reached out to Rivian with this question and they passed it on too you the Rivian community, they real had, to my suprise no insight.
Here was their response.

"Thanks for reaching out! There are many subjective variables, but generally, I can say these are probably the best rules of thumb:

• Keeping your vehicle at 100% SOC consistently is not the healthiest for your battery.
• Leaving your vehicle unplugged can potentially result in your vehicle reaching 0%; in this scenario, this would also be detrimental to your battery and possibly require replacement.
• Keeping your vehicle charged between 20-70% seems to be the universal best practice.

I might say this question may be best posed to the online community. Battery chemistry can get very dense to digest and a rabbit hole of information to get into. Lots of helpful resources online but the forums are typically the best place to learn about EV practices.

Stay adventurous,
Michael
Sr. Inside Delivery Guide"

So here I am, what are your practices and general thoughts on daily charging vs charging when needed?

This is one of the best videos I have seen on this subject, which dives into the battery chemistry.

 

[Meltdwn]

This guy seems pretty smart and seems to say you should do frequent small charges if possible. I’ll let you decide how much stock to put in to YouTubers recommendations.

This explanation makes the most sense and is engineering/science based. What a group of people generally do, should have no weight. Lots of crowds have destructive practices.

My big takeaway from this video is that charging to 100% or depleting to zero (even for a minute) does a little bit of damage. At 100%, the “ crystals” develop cracks. It doesn’t take hours at 100%, once you stop charging, they stop expanding. Leaving it at that state for hours is no worse than reaching 100%. The micro damage is done.

Maximum battery life is maintained with charge state between 20% and ~70%. For maximum vehicle utility, we sometimes need to go above or below these levels. Even in doing so, there are many, many “lifetime miles” in our batteries.

 

[s4wrxttcs]

It doesn’t take hours at 100%, once you stop charging, they stop expanding. Leaving it at that state for hours is no worse than reaching 100%. The micro damage is done.

It's pretty engrained into most EV owners that leaving a battery at a high state of charge for a long time is bad.

The issue is understanding why this occurs, and how long is okay. If I'm going on a road trip tomorrow then obviously I'd prefer to charge to 100% while I'm sleeping versus charging to 85% and then trying to remember to charge to 100% right before I leave.

As I understand it there really isn't much difference in this scenario and either way is fine.

Where its really the act of leaving the battery at a high SOC for a long time that does the damage.

Here is what a battery university article has to say about it.

" Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling. Table 3 demonstrates capacity loss as a function of temperature and SoC. "

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries#google_vignette

It's also important to point out why an occasional charge to 100% is a good thing. It helps with the BMS calibration.

 

[s4wrxttcs]

If an an electrical engineer can tell me otherwise

I'm an Engineer

Not a Chemist!!

 

[s4wrxttcs]

You're battery charging routine is ideal.

The problem with this chart is it doesn't tell you the two most critical factors. Those are time and temp.

Additionally it doesn't tell you useful miles.

Like it has 75% to 65% looking better than 75% to 45%, but how many extra miles would that actually get someone? Their range between charging would be much smaller so they'd have to charge more often. It probably equals out in the end.

Now there is a lot of utility in always be charging. So I'm not opposed to those that do it. Hopefully EV's will come with inductive charger to make it easier to always be charging. Where inductive charging could even have a different charge limit to try to ensure 70% SOC or something like that.

 

[Robin]

My charging habits are built around my needs, and my understanding of battery longevity. Where I don't do anything that would drastically harm the battery, but at the same time I try not to allow the vehicle to get in the way of my needs.

A few times a month I charge to 100% right before a journey of around 215 miles. This allows me to get to my Oregon Coast house with about 60 miles in range left even without using conserve mode. Then I charge it to 70% or 85% overnight. Usually I spend a few nights there and charge back up to 100% right before my journey home.

That's really the only actual strain on the battery.

The rest of the time I'm typically go from 80% to 30% and then charge back up, but I don't charge every night. I charge on an as-needed basis. The average percentage that it sits is around 50%.

The only rule I follow is not to allow the battery to stay at a high state of charge for very long, and not to allow it to get to low or to stay low. The lowest I've gone down to is around 20-25 miles, but I charged as soon as I reached my destination. When it comes to how low I should go its less about the battery and more about what happens to the vehicle when a battery is too low to charge the 12VDC battery.

I rarely L3 charge not because of battery concern with fast charging, but I rarely need to.

When your battery reaches 10% or lower , you’ll get a warning . I’ve learned when I’m traveling, I’m watching my battery usages verses the miles. I don’t think you’d want your battery to get lower than 9-10% as this could cause some range anxiety and warning messages on the dash, I know because I’ve been there ..

 

[HaveBlue]

The problem with this chart is it doesn't tell you the two most critical factors. Those are time and temp.

Additionally it doesn't tell you useful miles.

Like it has 75% to 65% looking better than 75% to 45%, but how many extra miles would that actually get someone? Their range between charging would be much smaller so they'd have to charge more often. It probably equals out in the end.

Now there is a lot of utility in always be charging. So I'm not opposed to those that do it. Hopefully EV's will come with inductive charger to make it easier to always be charging. Where inductive charging could even have a different charge limit to try to ensure 70% SOC or something like that.

The graph displays battery capacity over the number of charge cycles. What's vague is what is considered a cycle? If 75-65 is a cycle then you're better off doing 20-70 because you got 5x the power/range from one cycle. Who cares if you can get double the cycles by only using 10% of the battery when you could get 50% of the battery with half the cycles. It comes out to 2.5x more miles driven. Anyway, it models that more conservative swings in the battery promotes more usable cycles/life.

I do 20-70% which is half the battery. Charging more often would be super annoying to me even at home. I have to say the 400+ range Audi doesn't have to stop at gas stations very often.

 

[djsider2]

The graph displays battery capacity over the number of charge cycles. What's vague is what is considered a cycle? If 75-65 is a cycle then you're better off doing 20-70 because you got 5x the power/range from one cycle. Who cares if you can get double the cycles by only using 10% of the battery when you could get 50% of the battery with half the cycles. It comes out to 2.5x more miles driven. Anyway, it models that more conservative swings in the battery promotes more usable cycles/life.

I do 20-70% which is half the battery. Charging more often would be super annoying to me even at home. I have to say the 400+ range Audi doesn't have to stop at gas stations very often.

Thanks for confirming the chart looked suspicious. I was going to ask about why this chart didn’t convert to a common metric since number of cycles is different in all of those charging scenarios.

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