Battery not regularly exercised - should I run battery down to 20% occasionally?

[briloop]

My vehicle: 2021 Tesla Model Y.

Current mileage as of December 15, 2023: 14,245.
Average miles per year: 4,748.
Average miles per day: 39.

I average one road trip a year of about 1,600 miles. Maybe three trips a year of 120 miles each on a freeway. When not in use, my car is plugged in to my level 2 charger. The charging limit is set for 70%. So, typically, I start the day with a 70% charge, use about 10% per day, and then the battery is charged back up to 70% at night.

According to an episode [Full Show: Clark Stinks! and Benefits of Hearing Aids (go to minute 14:57)] of Clark Howard's YouTube channel , one of Clark's viewers stated that he owns a shop that deals with used EVs. He said:

1. If an EV battery is not regularly exercised, between 20% and 80%, the battery will fail prematurely.
2. The majority of batteries he replaces in his shop are for vehicles between 7 to 10 years old and have fewer than 60,000 miles on them.
3. It is recommended that owners of EVs should drive at least 7,000 miles a year.

Is this true? Should I let my battery go down to 20% occasionally? How often should I let the battery go down to 20%?

Thanks

 

[GtiMart]

I don't think the failure thing is true at all, at least for a Tesla, and I'm sure AAKEE or someone else will chime in and provide the actual details. Keeping your battery in the same small SOC range reduces the BMS' ability to properly estimate capacity. You *might* end up stranded when the car thinks there's a few percent left. That's even more true of LFP batteries. But that's about the extent of the "damage" you'll do.

 

[LoudMusic]

What kind of cars is he replacing batteries in? That makes a world of difference.

 

[briloop]

The guy who made the statement about premature battery failure did not specify which vehicles were involved.

Electric cars made for the U.S. market in 2013 include the Nissan Leaf, Ford Focus Electric, Honda Fit EV, Scion iQ EV, Mitsubishi i-MiEV, Smart Electric Drive, Fiat 500e, Coda Sedan, Toyota RAV4 EV, and the Tesla Model S. Please be more specific.

I'm not well-informed on battery technology, so, the listener's claim on premature battery failure may not be accurate for vehicles manufactured within the last five years.

 

[ucmndd]

Is this true?

it all sounds like complete and utter horseshit to me.

 

[jjrandorin]

The guy who made the statement about premature battery failure did not specify which vehicles were involved.

Electric cars made for the U.S. market in 2013 include the Nissan Leaf, Ford Focus Electric, Honda Fit EV, Scion iQ EV, Mitsubishi i-MiEV, Smart Electric Drive, Fiat 500e, Coda Sedan, Toyota RAV4 EV, and the Tesla Model S. Please be more specific.

I'm not well-informed on battery technology, so, the listener's claim on premature battery failure may not be accurate for vehicles manufactured within the last five years.

What car(s) the person is talking about is probably one of the most relevant variables, right?

Otherwise this is no different than a mechanic saying " I work on cars and car engines" and then making statements about modern car engine durability vs engines built 20 years ago.

 

[E90alex]

If you drive that little, set the charge limit to 50. Increase it as needed for longer trips.

 

[AAKEE]

1. If an EV battery is not regularly exercised, between 20% and 80%, the battery will fail prematurely.

There is no research test data at all supporting this.
Lithium ion batteries have no memory effect, and calendar aging is the thing causing the largest degradationnthe first 5-8 years. You can leave a battery unused for one year and it will work fine after that.

Low SOC causes the lowest calendar aging, and small cycles at low SOC causes the lowest cyclic aging.

2. The majority of batteries he replaces in his shop are for vehicles between 7 to 10 years old and have fewer than 60,000 miles on them.

Calendar aging take a big bite and should be the absolute biggest factor for degradation during the 7-10 year span.
In fact, degradation should probably not be the main reason for these fails. But water leaks, connectors coming loose inside the battery for balancing circuits and failures of the BMS and BMB should be most common…

3. It is recommended that owners of EVs should drive at least 7,000 miles a year.

I’d say that it doenst matter.

But as most people charge to 80-90%, a little more driving probably reduce the average SOC, reducing degradation.

Is this true? Should I let my battery go down to 20% occasionally? How often should I let the battery go down to 20%?

You never need to do that.

But down to 0% is not bad for the battery and 100% is not as all as bad as the rumor says, so you can use 0-100% if/when needed but the battery do not need it.

I have some tesla cells (Panasonic 2170) that now have been layoung around for ~1 year. I did some calendar aging tests with them during about one year. After this I did leave them in the same SOC as during the tests. I’ll check them soon but I bet they still work fine! Even the ones that been at 100% for about two yrs.