Best LFP Charging Practices when going on vacation?

[MrMime2]

I am planning on taking a 3 week vacation soon and will be leaving my M3 RWD in the garage for the duration. What is the best way to take care of the battery? Regularly, I'll drive the car down to about 30-40% and charge it back up to 80% - then also make sure to charge it to 100% once per week.

Since this is a 3 week trip do I need to charge the car up to 100% and unplug it before I leave? I've also heard leaving the car at 50% plugged in is good but what about Tesla's recommendation of charging it to 100% once per week? Is it fine to charge the car to 50% and unplug it? Then once I get back just plug the charger back in and top it off to 100%?

 

[Tam]

I am planning on taking a 3 week vacation soon and will be leaving my M3 RWD in the garage for the duration. What is the best way to take care of the battery? Regularly, I'll drive the car down to about 30-40% and charge it back up to 80% - then also make sure to charge it to 100% once per week.

Since this is a 3 week trip do I need to charge the car up to 100% and unplug it before I leave? I've also heard leaving the car at 50% plugged in is good but what about Tesla's recommendation of charging it to 100% once per week? Is it fine to charge the car to 50% and unplug it? Then once I get back just plug the charger back in and top it off to 100%?

From the manual:

"The most important way to preserve the high voltage Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model 3 for several weeks."

"For RWD vehicles: Tesla recommends you keep your charge limit to 100%, even for daily use, and you regularly charge your vehicle to 100%. If Model 3 has been parked for longer than a week, drive your vehicle as you normally would and charge to 100% at your earliest convenience."
Once per week is minimum if you can't do daily.

 

[Dave EV]

To minimize the rate of capacity loss while you're away, I would do one of the following (ignore the owner's manual):

1. Charge to 50% and leave it plugged in.
2. Charge it over 40% and leave it unplugged.

When you get back, charge it to 100%.

Typical rate of discharge over 3 weeks won't be more than a few percent a week, so you shouldn't lose more than 10% over 3 weeks.

 

[hgmichna]

To minimize calendar degradation, set it to 70% and leave it plugged in. Calendaric degradation is roughly the same in the 40% to 70% range, so it's no use setting it lower, although you can, if you like.

 

[NeverGoingBack]

ignore the owner's manual

As a general rule, I personally always do the opposite. I like to read the instructions before using something new, too. I might be in the minority, but it has worked for me over the years.

 

[MrMime2]

To minimize the rate of capacity loss while you're away, I would do one of the following (ignore the owner's manual):

1. Charge to 50% and leave it plugged in.
2. Charge it over 40% and leave it unplugged.

When you get back, charge it to 100%.

Typical rate of discharge over 3 weeks won't be more than a few percent a week, so you shouldn't lose more than 10% over 3 weeks.

Would it be better to leave it plugged in with the charge limit set to 50%? Then when I get back just charge it to 100% before driving it again?

I noticed the idle battery drain is not bad. I could also easily charge it to 50% and leave it unplugged until I get back but what’s better for the battery?

 

[Ther0ck]

Read the user manual. The info is inside.

 

[E90alex]

Would it be better to leave it plugged in with the charge limit set to 50%? Then when I get back just charge it to 100% before driving it again?

I noticed the idle battery drain is not bad. I could also easily charge it to 50% and leave it unplugged until I get back but what’s better for the battery?

Either way would be essentially the same for the battery as long as there’s no weird phantom drain.

Leaving it plugged in would prevent any rogue phantom drain from possibly completely draining the battery while you’re away so I would personally leave it plugged in at 50% and charge it back to 100% upon returning.

 

[3sr+buyer]

Would it be better to leave it plugged in with the charge limit set to 50%? Then when I get back just charge it to 100% before driving it again?

Yes, leaving it plugged in with the charge target set to 50% is likely the best for the battery (actually any level below 70% should be fine for LFP batteries). Leaving it plugged in will avoid vampire drain pulling it down below 0% if such unexpected vampire drain occurs (e.g. if you left draining features like sentry mode on, or you have some app checking the car often).

When you get back, charge it back up to 100% before doing a significant drive.

 

[Leafdriver333]

Nobody knows.
Report back in 100000 miles or 8 yrs

 

[Dave EV]

As others have posted, the rate of capacity loss of LFP cells is basically the same from about 40-70% - probably due to the same factors that give it the very flat discharge curve. So for 3 weeks, whether you leave it plugged in or unplugged if you start at 50% or higher, it's not going to make a difference.

The lower the SOC the better for storage - this is true for for all lithium based chemistries. The BMS will not let you discharge it low enough to damage the pack, but going too low will eventually require extra steps to bring the car back to life.

For those who say "just do what the manual says and keep it plugged in and charged up!", you have to recall that Tesla is balancing multiple needs and not only just maintaining maximum capacity over time. They only care that it doesn't degrade so fast that it causes the pack to be replaced under warranty and that things are as easy as possible for the operator. This means charging to a higher SOC and plugging in and charging all the time to minimize range anxiety.

@AAKEE has posted lots of research on various chemistries over the years. Here's a screenshot of the a lithium calendar life study he posted, along with more details in the post linked below that covers the differences:

https://teslamotorsclub.com/tmc/posts/7312004/

 

[AAKEE]

Adding on to @Dave EV ’s good post:

We can se at teslalogger.de that a Model3 LR with NCA looses about 5% range at 50K km, and at the same range SR’s with the LFP’s loose slightly less, like 4% at 50K km (pictures below)
[Time] would be a better unit, but people havent started thinking in time yet.

We know that LFP should be able to do litterally thousands of cycles so the about 160 FCE cycles at 50K miles should not cause any noticable degradation.

The conclusion is that the degradation we can see is calendar aging. This is also what we ( I ) expected, but as chemistries get developed we could not be 100% sure when the model 3 did get the LFP’s.
Now we can be quite sure about this, meaning that it is possible to reduce the degradation with the same tactics as for NCA cells (adjusted for the higher central graphite peak).
Its still needed to charge full often enough to let the BMS keep track of the SOC, but if charging late/shortly before the drive and otherwise keeping below 70% the degradation should be cut in half
From 40-65% seems to be a very good spot (lower SOC is not bad at all though).

80-90% seem to be what to avoid to keep the degradation low.

The graph above combines two different ranges, but the initial range for the lower range was 424 km I think.
The higher range was about 440km and will be at approximately 420km at 50K km.

 

[rpiotro]

...The lower the SOC the better for storage - this is true for for all lithium based chemistries. The BMS will not let you discharge it low enough to damage the pack, but going too low will eventually require extra steps to bring the car back to life....

Like 10%? I don't believe this is true. It is my understanding that if you keep the SOC between 70% and 40% you can extend the life considerably. Even 80%-30% is close enough. I believe Musk said 80/20. With 50% being optimal for long term storage.

I can practice 70/40 almost all of the time because my daily use is low.

 

[nurusz]

I am planning on taking a 3 week vacation soon and will be leaving my M3 RWD in the garage for the duration. What is the best way to take care of the battery? Regularly, I'll drive the car down to about 30-40% and charge it back up to 80% - then also make sure to charge it to 100% once per week.

Since this is a 3 week trip do I need to charge the car up to 100% and unplug it before I leave? I've also heard leaving the car at 50% plugged in is good but what about Tesla's recommendation of charging it to 100% once per week? Is it fine to charge the car to 50% and unplug it? Then once I get back just plug the charger back in and top it off to 100%?

My 2021 Tesla 3 SR+, not connected to the charger and with sentry mode off, only lost 2% in 13 days

 

[AAKEE]

Like 10%? I don't believe this is true. It is my understanding that if you keep the SOC between 70% and 40% you can extend the life considerably. Even 80%-30% is close enough. I believe Musk said 80/20. With 50% being optimal for long term storage.

I can practice 70/40 almost all of the time because my daily use is low.

Nope, you are cought by the myths.

The lower the SOC down to 0% the less calendar aging.
The picture shows degradation as a result from different SOC. Its easy to see that low SOC is better.

Low SOC is also better for cyclic aging, as small cycles is.


Elon Musk is not going to tell us what gives the lowest degradation. He is going to tell is what the Tesla company want the most people to know.

That Elon Musk statement you refer to is probably the famous statement?

 

[rpiotro]

Nope, you are cought by the myths.

The lower the SOC down to 0% the less calendar aging.
The picture shows degradation as a result from different SOC. Its easy to see that low SOC is better.
View attachment 926594

Low SOC is also better for cyclic aging, as small cycles is.


Elon Musk is not going to tell us what gives the lowest degradation. He is going to tell is what the Tesla company want the most people to know.

That Elon Musk statement you refer to is probably the famous statement?
View attachment 926595

I think this gentleman may disagree with you. You can skip to 15:14 if you like. Of course this is with conventional Li-ion batteries.

I sincerely believe there have not been enough hours in service for the LFP batteries to really know the truth

The Truth About Tesla Battery Degradation – and Other EVs - YouTube

 

[AAKEE]

I think this gentleman may disagree with you. You can skip to 15:14 if you like. Of course this is with conventional Li-ion batteries.

I sincerely believe there have not been enough hours in service for the LFP batteries to really know the truth

The Truth About Tesla Battery Degradation – and Other EVs - YouTube

I do not know for sure what you are refering to, but if we start with the chart he shows about DoD.…
Oiiiihhh, here we go again:

This is a chart stolen from the same badly managed research report that batteryuniversity refers to.
There is a number of faults with the test behind this chart and the application in this case and the batteryuniversity case.
-First of all, all these charts that should tell us whats best for use in EV’s (and for most other usage) should use FCE, Full cycle Equivalent or Amphere hours on the X-axis.
This chart actually is fooling you.
The white 75-65% line has pushed 400FCE at the 4000 cycles mark and lost about 6%. Thats 66.7 FCE / lost percent of capacity (400/6)
The red line with 100-25% has done 3000 FCE (75% DoD x 4000 cycles) and lost about 21%. Thats 142 FCE cycles per lost percent capacity (3000/21).
In this case this means that his graph tell us that the 100-25% is better than 75-65%.
This do not ad up to the real life tests that other researchers tests show. The original research report use the term ”dynamic stress cycle” which they do not explain what they mean at all. As it looks, it could be FCE, but they do not say, state or explain it. Thats bad…

The other thing is that that research report do not even try low SOC cycles. It is impossible to safely be able to say that 75-65% is the best cycling range if you did not try them.

Pic’s from the original report.
This test was supposed to (caviat for not explaining their weird results good enough) only show that smaller DoD is better than bigger DoD as there is only one cycle test with 10% DoD. We would need at least a couple more at the same DoD but at differebt SOC, like 10-0% or 20-10%

There is two cycles with 50% DoD (100-50 and 75-25%). These show is that at the same DoD lower SOC cycling is better. There is no low SOC cycles at the same range so we can not say anything about what is the optimum SOC range as this test do not cover that at all.

There is some more issues with this research report/test. But the two big issues is that they fail to show us what they ment with dynamic stress cycles which rendercthe result both strange, and also not pissible to draw any conclusions. The second issue is that the test is not at all setup to find the best cycling range, as they did not test any low SOC range to compare with.
There are conclusions we can draw, assuming that they ment FCE when they wrote dynamic stress cycle: low SOC range is better than high SOC range and smaller cycles(DoD) is better than large. But that we already did know.

I have written about this research multiple times before (not only me that did that) so a search here for DST pr dynamic stress cycle will get you there. There would also be a link to the original research report, but I do not recommend to read it.

All other (well there is a few other bad reports, but 99% is good) research reports tell us the same thing. The researchers are agreeing quite well about both cyclic and calendar aging.

 

[AAKEE]

Here is that report:
Research report, not recommended to read

So, they did no real battery tests, but did get the test data from the LMO cell manufacturer.

Then they….simulated it in a computer.

And, without any own testing or any data for this, they decided that low Soc was bad for cycling:

In particular, the three test cases starting at 100% SoC, represented by the black (100- 25), red (100-40), and dark blue (100-50) curves in Fig. 5a, show a very fast degradation rate during the early cycles. This early degradation causes an obvious gap between the dark blue curve and the green curve (85-25) in the test data. This phenomenon is possibly due to cell over-voltages caused by high SoC during cycling.

”Cell overvoltage” doesnt happen with correct Charging protocols up to 100%.
As it was the manufacturer only that actually had performed any tests, we could-should expect the charging to be professionally performed.

 

[MrMime2]

So much analysis in this thread way above my pay grade

I guess before I go on vacation I'll drive my car down to about 50% and just leave it unplugged in my garage the entire time and charge it back up to 100% when I get back before I drive it again.

 

[rpiotro]

So much analysis in this thread way above my pay grade

I guess before I go on vacation I'll drive my car down to about 50% and just leave it unplugged in my garage the entire time and charge it back up to 100% when I get back before I drive it again.

Why not plug it in and set the max charge top 50%? Insurance.