Should I still be Charging to 80%?

[illy_gilly]

Hey guys had a question regarding charging that I was hoping to get some information on.

So before I got my M3, I remembered reading earlier on from a tweet from Elon that an 80% SOC was ideal for battery health with regards to daily commuting.

After having my car for a week, I've noticed that I really am not driving all that much. In the last 10 days I averaged anywhere between 10-20% of battery usage. The most I have used so far has been around 25% which brought me down to 55% battery, and this was a complete outlier day, and I don't expect many of these at all. So I'm wondering in an effort to maintain the life of my battery should I still be charging to 80%, or should I think about reducing it down. Is the difference between 80% SOC and say for example 70% so negligible in the long run that it doesn't really matter?

Would love to hear your thoughts!

 

[Nixx]

The battery likes to be between 20-80%. Maybe 30-70 is slightly better, but it's likely negligible.

The problem with maintaining a charge lower, like say 50%, is that if you DO need the energy, you are going to have a problem. Like, if you need to go to a shop that's outside your normal path, or in a different area of the city that's further away. You don't want to start worrying about your range.

Also, you are in Canada. The cold temperature will completely destroy your range. In the summer, I use less than 10% to work and back. In the winter I could use 50% on ultra low -40c days.

 

[KenC]

There's a thread, Battery Degradation Scientifically Explained, that has alot of info so that you can make up your own mind on the approach you'd like to take.

I used to charge to 90%, when I got my car in December, then when Spring hit, I switched to 80%. Then after reading the above thread, I decided to experiment and charge only to 60%. Of course, if I go somewhere far, I charge up to 90%. So far, minimal degradation as far as I can tell after almost 2 yrs.

 

[M3BlueGeorgia]

I've got recently switched to 70% for routine overnight charging.
But still 90% for road trips.

 

[mswlogo]

I've got recently switched to 70% for routine overnight charging.
But still 90% for road trips.

Thats what I do. If I know I’m going somewhere I just bring it up to 90. And 70% is usually enough for a longish unplanned trip.

 

[TimothyHW3]

The main thing to take from all the other threads is that Model 3 doesn't like small increment charging. For example bringing it down to 50/70% and charging to 80-90% will mess up the BMS and you will massively loose range over the long run.
So just try to always drive it down to 10/20% and only then charge to 80/90%, that is the only rule.

Frankly, the BMS seems to be a bigger issue with these batteries than real degradation so make sure you charge it like that and don't worry.

 

[joefee]

I have a 2017 M3 LR and have aways charged 70-90% and full charge is 315 as of yesterday. 90% of my drives are very short trips.

 

[Dave EV]

The main thing to take from all the other threads is that Model 3 doesn't like small increment charging. For example bringing it down to 50/70% and charging to 80-90% will mess up the BMS and you will massively loose range over the long run.
So just try to always drive it down to 10/20% and only then charge to 80/90%, that is the only rule.

Frankly, the BMS seems to be a bigger issue with these batteries than real degradation so make sure you charge it like that and don't worry.

Just to clarify, if seems that to make sure the BMS accurately reflects capacity, it does have to see a variety of states of charge, otherwise it can get inaccurate and may result in lower mileage readings.

For highest cycle life, it's best to keep the SOC around 50%, if you only use 10-20% of the battery most of the time, charging to 60% should reduce rate of capacity loss, but then don't be afraid to charge as high as you need for any trips.

 

[TimothyHW3]

For highest cycle life, it's best to keep the SOC around 50%, if you only use 10-20% of the battery most of the time, charging to 60% should reduce rate of capacity loss, but then don't be afraid to charge as high as you need for any trips.

The best SOC in terms of life span is to keep the battery between 45 and 70% or even 55% and 65% according to the battery university and the Voltage on Model 3. So if you want to keep the car on hold for longer periods, that should be SOC you leave it.

For daily operations that is unpractical.

I have seen people charging to 60% only and even though their BMS shows a higher state of health, their BMS is still a bit unbalanced, but on the other end - overprojecting. So that could leave to issues if you drive it down to 0%.

I still think charging and doing larger increments 10/20 to 80/90% is the best approach, based on my experience and 30,000miles.

 

[Rocky_H]

The main thing to take from all the other threads is that Model 3 doesn't like small increment charging. For example bringing it down to 50/70% and charging to 80-90% will mess up the BMS and you will massively loose range over the long run.
So just try to always drive it down to 10/20% and only then charge to 80/90%, that is the only rule.

Frankly, the BMS seems to be a bigger issue with these batteries than real degradation so make sure you charge it like that and don't worry.

You are talking about two massively different things, which have opposite tactics. It is undisputed that for the real health of the physical battery, staying near a middle state of charge is the most beneficial in reducing the damage/degradation.

What you are talking about, though, is trying to help the software with keeping a more accurate reading of the energy contained in the battery. The charging practices you are talking about, with letting it run down lower and charging it up higher do help to give people that "warm fuzzy" feeling by keeping that number accurate, but at the expense of doing more long term damage to the battery. So a lot of this is up to which people prefer to prioritize.

 

[TyH2009]

Interesting, maybe I should stop getting down to about 50% then charging back up to 80%, that seems to be my routine ever 3ish days or so.

 

[TimothyHW3]

You are talking about two massively different things, which have opposite tactics. It is undisputed that for the real health of the physical battery, staying near a middle state of charge is the most beneficial in reducing the damage/degradation.

What you are talking about, though, is trying to help the software with keeping a more accurate reading of the energy contained in the battery.

Thank you for summerizing exactly what I said in different words...

The charging practices you are talking about, with letting it run down lower and charging it up higher do help to give people that "warm fuzzy" feeling by keeping that number accurate, but at the expense of doing more long term damage to the battery.

And you know that...because?

If you actually see the diference between 25-80% charges comparing to let's say 45%-75% the difference is so small, 2% or 3% better health at 2000 cycles (or around 600.000 miles)

https://batteryuniversity.com/_img/content/DST-cycles-web2.jpg

Plus more people will charge 50%-80%/90% and not 45% to 75% so the health benefits will deminish as keeping the car on high SOC is very bad.

And no, it is not just a warm fuzzy feeling - if your BMS is unbalanced you have less range. Even if you don't really and your battery is healthier.

So keeping the BMS happy is the only way to go to have range. If you don't care about range and you plan on charging 60%-80%, you might as well get an SR+ and forget about it.

For anyone who likes to use the maximum of the battery and go down to 0% from time to time when needed - the happy BMS is the way to go.

 

[CyberGus]

The BMS was architected on the outdated assumption that when the car is not driving or charging, it would be "off" and available for measurement. With the additional standby functions (Sentry, Summon, Overheat, etc.) this is rarely true.

I propose that the pack should be in two halves. Both would be used as per usual when driving or charging, but when on standby functions, only 1 side of the pack would discharge while the BMS measured the idle half. When the measurements complete, the two sides would change roles.

 

[Dave EV]

Interesting, maybe I should stop getting down to about 50% then charging back up to 80%, that seems to be my routine ever 3ish days or so.

Honestly, this is probably as good as anyone really needs to worry about. In non-COVID times I usually go 70-80% down to 30-40% or so for two reasons:
1. Lower average SOC should result in slower battery capacity loss (there is some conflicting data in terms of what happens at very slow SOC, below 10-15% or so).
2. I'm too lazy to plug in every day and this is a reasonable compromise in usability. I could plug in every day and charge to 50-60%, for example.

If you actually see the diference between 25-80% charges comparing to let's say 45%-75% the difference is so small, 2% or 3% better health at 2000 cycles (or around 600.000 miles)

https://batteryuniversity.com/_img/content/DST-cycles-web2.jpg

https://batteryuniversity.com/_img/content/DST-cycles-web2.jpg
Note that this is a rapid cycling test - in real life, significant time is spent at various SOC which will changes the results. Though I still expect the difference to be minor. I would have liked to have seen a 55-25% and 45-25% cycle test, for example, or perhaps a 55-45% cycle test.

So keeping the BMS happy is the only way to go to have range. If you don't care about range and you plan on charging 60%-80%, you might as well get an SR+ and forget about it.

For anyone who likes to use the maximum of the battery and go down to 0% from time to time when needed - the happy BMS is the way to go.

Well, that's quite the jump. While the BMS does seem to lose some paper range if you keep the car in a narrow SOC band, it remains to be shown how much real life range is actually lost due to imbalance.

 

[TimothyHW3]

. While the BMS does seem to lose some paper range if you keep the car in a narrow SOC band, it remains to be shown how much real life range is actually lost due to imbalance.

This does seem to come all the time and I am not sure where the "paper range" argument really comes from or came from.

What you see IS the range you will get - the miles are representation of kWh. If you do mental math, anytime you see miles on display you can easily turn that into kWh available.

Trust me, if the car thinks you have X amount of kWh - even if there are theoretically more, you can't use them as the BMS will not allow you to...If anything, the "paper range" you are referring to will be anything the BMS doesn't know exists, not what you see on display.

 

[Rottenapplr]

Hey guys had a question regarding charging that I was hoping to get some information on.

So before I got my M3, I remembered reading earlier on from a tweet from Elon that an 80% SOC was ideal for battery health with regards to daily commuting.

After having my car for a week, I've noticed that I really am not driving all that much. In the last 10 days I averaged anywhere between 10-20% of battery usage. The most I have used so far has been around 25% which brought me down to 55% battery, and this was a complete outlier day, and I don't expect many of these at all. So I'm wondering in an effort to maintain the life of my battery should I still be charging to 80%, or should I think about reducing it down. Is the difference between 80% SOC and say for example 70% so negligible in the long run that it doesn't really matter?

Would love to hear your thoughts!

Im working at home and I was charging to 50%. I’ve since up it to 60%. I usual drive around town after work cause I’m very claustrophobic Just a personal preference. Plus we just got a new supercharger installed on the other side of town so in the even I need to charge ASAP, it’ll take me 30 mins to total including driving and sitting on the charger to get to 90% for an unplanned road trip.

 

[Darmie]

Hey guys had a question regarding charging that I was hoping to get some information on.

So before I got my M3, I remembered reading earlier on from a tweet from Elon that an 80% SOC was ideal for battery health with regards to daily commuting.

After having my car for a week, I've noticed that I really am not driving all that much. In the last 10 days I averaged anywhere between 10-20% of battery usage. The most I have used so far has been around 25% which brought me down to 55% battery, and this was a complete outlier day, and I don't expect many of these at all. So I'm wondering in an effort to maintain the life of my battery should I still be charging to 80%, or should I think about reducing it down. Is the difference between 80% SOC and say for example 70% so negligible in the long run that it doesn't really matter?

Would love to hear your thoughts!

I thought it was mention to charge to 90 %

So, who do you believe.

 

[Rocky_H]

I thought it was mention to charge to 90 %

Tesla has told their employees to tell that to everyone because it's a marketing answer. It's not best for the battery, but if they told people lower, people would be complaining all over the place about how this piece of $#it car is unusable because it doesn't have enough range because they're not supposed to charge very high, so it only has 100 miles of range, etc. etc. And they don't want to have to have their sales people discuss every single person's unique driving and charging situation to come up with different answers all the time, and then people would be arguing and criticizing Tesla for saying different answers. So they just give one standard number that works decently OK for everyone.

So, who do you believe.

Oh really? You want to go there?
Maximum charge level for daily use

Quote from Musk when asked about recommended charging range: "80% to 30%"
Quote from Jeff Dahn, the most world renowned expert in lithium ion batteries, who does work with Tesla now: "I would recommend charging to 70% normally. When you need a long trip, charge to 100%."

It bugs me that someone filmed that video with bad information and then people started sharing that all over the place as if it's gospel.

 

[KenC]

Just to add to Post #3, 90% of my daily commutes are less than 30 miles. I now charge to 60% and driving 30 miles means I usually get home with 50%, so I cycle between 50 and 60%. I haven't had any BMS drift issues, though my car sits outside in cold Maine. The slight variation is ambient temperature related; otherwise, it's showing no change at all.
Here's what Stats shows:

 

[Rottenapplr]

Tesla has told their employees to tell that to everyone because it's a marketing answer. It's not best for the battery, but if they told people lower, people would be complaining all over the place about how this piece of $#it car is unusable because it doesn't have enough range because they're not supposed to charge very high, so it only has 100 miles of range, etc. etc. And they don't want to have to have their sales people discuss every single person's unique driving and charging situation to come up with different answers all the time, and then people would be arguing and criticizing Tesla for saying different answers. So they just give one standard number that works decently OK for everyone.

Oh really? You want to go there?
Maximum charge level for daily use

Quote from Musk when asked about recommended charging range: "80% to 30%"
Quote from Jeff Dahn, the most world renowned expert in lithium ion batteries, who does work with Tesla now: "I would recommend charging to 70% normally. When you need a long trip, charge to 100%."

It bugs me that someone filmed that video with bad information and then people started sharing that all over the place as if it's gospel.

Super agreed. Not gonna take some youtuber advice as Gospel. Companies such as Apple are now working to extend lithium life so they added optimized charging which is to charge to near the top, but stop charging until machine learning will determine when you typically get up and start using the device. That’s when the device charges to 100%. For my use and ITs MY DECISION TO MAKE, sitting at a high state of charge is not good for MY BATTERY. Therefore I made the decision for MYSELF to charge to 50-60 when I’m driving around town. When I had work commute I would charge around 70% to 80%. Usually it was 70% since I had a 100 mile commute and I have a long range model and charge at night anyway.

I don’t worry about when I need to charge to 90% when I’m driving a lot and I charge to 100% when I’m pushing range (like going to Yellowstone during the pandemic and the western Yellowstone charger wasn’t accessible/or sequoia where there’s no nearby supercharger) but again I don’t let the battery sit at a high state of charge for a long time.