Thanks. I charged my Model S to 90% for about 6 years and 80% for 5 years. Still has over 80% capactity. But just got a new one so I'll limit max SOC to something more reasonable. It has more range to 60% will get me farther than 80% of my old car.
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What should my ideal charge percentage be?
- Thread starter Al Sherman
- Start date
Based on the recent study that shows that cars supercharging 90% vs cars supercharging only 10% of the time have almost identical battery degradation. That suggest the charge speed has little effect.
What you might consider is the efficiency. If you charge at a lower rate you charge takes longer. That means the pumps and other things will run longer and use extra energy longer. That's why higher amps lead to a slightly more efficient charge. It's not a big difference though.
I think it might be worth you making a new thread we can sticky with everything you've written. So it isn't lost on a long post. Thanks. Great information.
12Pack
Member
Indeed would be good to introduce the concept of calendar aging to the wider community.
Most EV battery life discussion in the mainstream has been about cycle aging vs. storage SOC and charging speed.
Most EV battery life discussion in the mainstream has been about cycle aging vs. storage SOC and charging speed.
Why not an AI-driven ‘suggested charge’ based on your driving history & ambient conditions? That would be nice….say 30% is your typical need ( 30% down to 20 ) but on a cold day, the car adds some additional SoC to compensate for low ambient temps. Especially useful if you have L2 because the car can quickly add charge. L1 is just too slow to optimize daily charge like this.
Sounds like Tesla can add it. I'd suggest pulling in the weather forecast and help with the predictions.
So far I am just using AI without the A, to manage my charging. It has really paid off for us. Even my wife is finally onboard and just leaves it at 50% to make it easy. With the really cold (for Texas temps), we've been at 60% since calendar aging isn't going to be as much an issue with sub-freezing temps.
So far I am just using AI without the A, to manage my charging. It has really paid off for us. Even my wife is finally onboard and just leaves it at 50% to make it easy. With the really cold (for Texas temps), we've been at 60% since calendar aging isn't going to be as much an issue with sub-freezing temps.
Thanks for all the information you have posted here. I will definitely try to advise people against the ubiquitous 80% that gets posted everywhere.
I am also greatly relieved that cyclic aging isn't really an issue, i am a high mileage driver so i might see the 300k kms i got out of my previous diesels if i keep the storage SOC nice and low.
Most of the above is for NCA batteries, is it basically the same advice for the LG NMC batteries in the MIC RWD MY/M3 that we get in UK/Ireland?
I have a June 2023 MYLR with 22k kms on the clock. Tessie app showing 1.9% degradation (not sure how accurate Tessie is).
I charge at work (because its free) and have approx 20% each way on the commute. I had being going to 75% just before leaving, putting me at 55 overnight and then 35 when i arrive back next day. Was afraid to go too low on the SOC as all the incorrect advice is not to go too low.
I wonder should i go a bit lower now, plan to arrive at work with 20% or less.
geordi
Mr Fusion V.1
The issue with the NMC batteries is the voltage curve they present to the BMS. It is nearly flat.
THESE NUMBERS ARE FAKE EXAMPLES ONLY:
For an NCA battery, it could be like an alkaline in a battery tester, where there is a linear progression. 1.6v is full, 1.5v is like 80%, 1.3v 50%, 1.2v is 25%, 1.0v is dead.
Since that is a predictable curve across multiple charge cycles, the BMS can have strong knowledge of the actual power available and give that information to the driver.
BUT in NMC batteries, the only concrete known points are when the battery is completely full and refuses to accept any more power, and the opposite when it is depleted and has no more power to give. In between, the voltage "curve" is nearly flat until you are almost dead. So the BMS needs the battery charged to 100% every once in a while to recalibrate, as it must monitor all the usage to calculate how much must be remaining at any given moment.
The owners manual for the NMC equipped cars SHOULD have this information, but I'd look around to see what the suggestion is for how often you should go to 100% for BMS calibrations. As far as I'm aware, the issue with doing this on an NMC battery is less damaging to total degradation than it would be on the NCA packs, so there's that.... BUT that also could just be Tesla lying by omission and not telling anyone that it is still hurting the battery, but won't hurt it in the now-limited warranty periods. I wouldn't put it past them.
THESE NUMBERS ARE FAKE EXAMPLES ONLY:
For an NCA battery, it could be like an alkaline in a battery tester, where there is a linear progression. 1.6v is full, 1.5v is like 80%, 1.3v 50%, 1.2v is 25%, 1.0v is dead.
Since that is a predictable curve across multiple charge cycles, the BMS can have strong knowledge of the actual power available and give that information to the driver.
BUT in NMC batteries, the only concrete known points are when the battery is completely full and refuses to accept any more power, and the opposite when it is depleted and has no more power to give. In between, the voltage "curve" is nearly flat until you are almost dead. So the BMS needs the battery charged to 100% every once in a while to recalibrate, as it must monitor all the usage to calculate how much must be remaining at any given moment.
The owners manual for the NMC equipped cars SHOULD have this information, but I'd look around to see what the suggestion is for how often you should go to 100% for BMS calibrations. As far as I'm aware, the issue with doing this on an NMC battery is less damaging to total degradation than it would be on the NCA packs, so there's that.... BUT that also could just be Tesla lying by omission and not telling anyone that it is still hurting the battery, but won't hurt it in the now-limited warranty periods. I wouldn't put it past them.
No, it is LFP chemistry that have a very föat voltage curve in the middle 20-80% or so.
LFP’s has a flat curve, not NMC.
NMC and NCA has very similar voltage curves.
geordi
Mr Fusion V.1
Ok - I stand corrected. Color me confused on the specific chemistry of the batteries, I thought there were only the two.
I can’t edit my previous post. But what I am referring to are the model three and Y vehicles which have the suggestion to charge to 100% I believe weekly because of that voltage curve.
Thanks for the clarification
I can’t edit my previous post. But what I am referring to are the model three and Y vehicles which have the suggestion to charge to 100% I believe weekly because of that voltage curve.
Thanks for the clarification
Yes. I have the rwd Lfp pack on a 3. I’ve pondered that same question on range accuracy versus degradation. I don’t like the battery sitting at 100%. So when I have charged to 100% it hasn’t been weekly. Also I like my wife to drive it right away after hitting 100% so I try to time the charge to finish right before she drives to work
From what I have been reading, I’ll be keeping my RWD 3 at 30-60% with bi-weekly charge to 100% for BMS reset, followed immediately by some highway miles to bring it down from 100% to the ~ 80% range before putting it back into the garage.
The RWD Y w/ NMC chemistry will get similar treatment except that we’ll limit the max charge to 95% and ONLY when needed by the navigation for longer (or colder) highway trips. Otherwise we’ll top the Y out at 80-90% and immediately drive it; so > 99% of its life will be at 60% or less.
Both of us have limited requirements for daily driving, so this should be very easy to manage. Upgrading to 240v charging by the time the hot weather arrives will give even more control of the calendar degradation since we can let them stay more in the 30-50% SoC range until needed.
Hopefully, this plan gets the AAKEE ‘seal of approval’!
aerodyne
2 of 3 EV's - Defect Free!
Another consideration might be that you loose Regen at 100%. I don't see a real downside to charging only to 93-95% regardless of chemistry.
I don't think bi-weekly charging to 100% is necessary or helpful. AAKEE knows way more than I do but I'd think just charging to 100% when you need it for a trip is likely good enough.
To follow the research data, the degradation is considerably lower at or below 70% displayed SOC.
( caviat: that this is not the exact number for all LFP, as changes in the chemistry can move the central graphite peak slightly in turn moving the point slightly.
It might not be very Important but as the LFP (as the other chemistries) sometimes show higher degradation around 80% or so, I thought it could be nice to know that so you do not drive around to lower the SOC and end up parking it at a SOC maybe not better than 100%
Se:
I had my Plaid for seven Months, and already have around 10 full charges.
I had about the same monthly rate for my M3P = 35 full charges during 2.5 years, and about 55 Supercharging sessions.
The battery capacity/ degradation was really good/ low.
There is not really necessary to limit the charge when traveling.
Cyclic aging during one year will be between 0.5% and 1% for most users. Mostly the lower number. Using the low SOC strategy will reduce the low 0.5 normal user normal annual degradation to maybe 0.25%. From this, only charging to 95% instead of 100% will probably not give a measurable difference.
But reducing the average SOC by staying at or below 55% most of the time, and charge late will Cut the calendar aging in half. Thats 2-3% reduction the first year and about 5-6% reduction in four-five years.
We can afford to use 100% any time we need to and still end up way below average like 50% lower than the normal car.
It OK.
Just think about not overdoing it.
I decided when I got my first Tesla not to let it go that far that it actually affected the joy of having a EV / Tesla.
It more or less have been that way. I remember a holyday trip with the family where there was no fast chargers near the overnight location and no nightly charging availabe. Was a warm summer week and I wanted to arrive with low SOC, like 20% or so, but I was torn between having an issue to being able to drive away the Next day.
After a while I realized that I had fallen in to the trap of being overprotective. It was possible to plan to arrive with 50% which actually is low enough and still being able to reach the next SuC.
I often see threads about minitous planning to save the every lithium molecule in the battery. It probably is not worth it. Just staying below that central graphite peak on the chemistry when possible like the mantra:
- do not charge more than you need (until the next charge)
- charge often ( reduces the needed amount above)
- charge late (Reduces the time at higher SOC, specially nice when more than 55% is needed).
Cuts the degradation in half, orBetter compared to the standard 80% charging started at arrival at home.
There is no point in which the battery is “full” or won’t take any more energy. Increase the voltage and the battery will have more charge all the way up to the point of thermal runaway. Picking 4.2v per cell is a trade off for safety, capacity, and life.
There is almost no point in doing this, as it just accelerates the deterioration of the battery. Ideally keep your state of charge at about 50-55% and charge up when you need more for the day.
I saw that one study about people who fast charge 90% of the time had almost no difference in degradation than those that did 10% fast charging. Does that line up with what you've read? I have free supercharging on the new car and there are so many more superchargers than before (and car charges incredibly quick compared to 2012 version) so might take advantage of it more.To follow the research data, the degradation is considerably lower at or below 70% displayed SOC.
( caviat: that this is not the exact number for all LFP, as changes in the chemistry can move the central graphite peak slightly in turn moving the point slightly.
It might not be very Important but as the LFP (as the other chemistries) sometimes show higher degradation around 80% or so, I thought it could be nice to know that so you do not drive around to lower the SOC and end up parking it at a SOC maybe not better than 100%
Se:
View attachment 1013438
I had my Plaid for seven Months, and already have around 10 full charges.
I had about the same monthly rate for my M3P = 35 full charges during 2.5 years, and about 55 Supercharging sessions.
The battery capacity/ degradation was really good/ low.
There is not really necessary to limit the charge when traveling.
Cyclic aging during one year will be between 0.5% and 1% for most users. Mostly the lower number. Using the low SOC strategy will reduce the low 0.5 normal user normal annual degradation to maybe 0.25%. From this, only charging to 95% instead of 100% will probably not give a measurable difference.
But reducing the average SOC by staying at or below 55% most of the time, and charge late will Cut the calendar aging in half. Thats 2-3% reduction the first year and about 5-6% reduction in four-five years.
We can afford to use 100% any time we need to and still end up way below average like 50% lower than the normal car.
It OK.
Just think about not overdoing it.
I decided when I got my first Tesla not to let it go that far that it actually affected the joy of having a EV / Tesla.
It more or less have been that way. I remember a holyday trip with the family where there was no fast chargers near the overnight location and no nightly charging availabe. Was a warm summer week and I wanted to arrive with low SOC, like 20% or so, but I was torn between having an issue to being able to drive away the Next day.
After a while I realized that I had fallen in to the trap of being overprotective. It was possible to plan to arrive with 50% which actually is low enough and still being able to reach the next SuC.
I often see threads about minitous planning to save the every lithium molecule in the battery. It probably is not worth it. Just staying below that central graphite peak on the chemistry when possible like the mantra:
- do not charge more than you need (until the next charge)
- charge often ( reduces the needed amount above)
- charge late (Reduces the time at higher SOC, specially nice when more than 55% is needed).
Better compared to the standard 80% charging started at arrival at home.
I'm still stopping charging at 55% so my stops are only about 5-8 minutes which is amazing. I can't believe how quick it is. 27-55% in 8 minutes.
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