I do mostly local driving (about 20 miles per day). A tech at the service center told me to charge my model 3 to 80% and not to charge it until it hits 40%. The owners manual says to keep it plugged in when not in use. Can anyone make sense of this for me? I'm charging it on a standard 3-prong household outlet.
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Periodic charging or?
- Thread starter Pasralph1
- Start date
It honestly barely matters for battery health whichever way you do it. The battery loses the least capacity due to degradation over time if it sits at 50%, but 80% max is a very safe level.
Do whatever is easiest for your commute/peace of mind/occasional longer drives that you need to do.
Do whatever is easiest for your commute/peace of mind/occasional longer drives that you need to do.
AlanSubie4Life
Efficiency Obsessed Member
Low cycle depth is definitely very good for lithium batteries, so definitely charge every day - it is also more convenient (maximizes average charge level), and it also makes it a habit, so you do not forget to plug in (a huge pain when you go to your car and it is not charged to your desired level).
Set the charge limit as high as necessary to meet your needs with margin, and no higher.
For you it sounds like 50% would be best.
If you have an LFP, follow the manual on that.
E90alex
Active Member
ABC - always be charging.
ESPECIALLY if you are just charging on 120v. Otherwise if you let it run down first it’s going to take you several days to charge it back up.
I set my charge limit to 57% and plug in every night when I get home. I only drive about 30 miles a day so even with 57% that gives me plenty of range.
But if you’re only using 120V it might be more convenient to just leave it at 80-90% because if you suddenly want more range for the weekend or for trips it would take you days to get from 50% to 90%.
ESPECIALLY if you are just charging on 120v. Otherwise if you let it run down first it’s going to take you several days to charge it back up.
I set my charge limit to 57% and plug in every night when I get home. I only drive about 30 miles a day so even with 57% that gives me plenty of range.
But if you’re only using 120V it might be more convenient to just leave it at 80-90% because if you suddenly want more range for the weekend or for trips it would take you days to get from 50% to 90%.
I'm a semi-retired technical analyst putting together a brief white paper on this kind of thing for friends and my own use. I'll PM you a copy if you'd be so kind as to proofread it for me. In the interim:
Tech's guy's pretty close. I'm still reading solid tech briefings and research links, but at this moment it looks like this:
1) Optimum cell voltage (3.92V) for best life translates into 70% charge of usable battery for non LFP. Higher is worse that lower, but both appear to matter. 5% either way starts to make a difference. I had mine set to 73% and moved it down to 70% today.
Charge speed vs temp matters, but the BMS handles this really well and hey, you're using 120V.
2) Depth of discharge (DoD) doesn't appear to be a big deal although research on it has lots of variables and gets pretty heavy fast. There is some mild cycle qty degradation that occurs, but well below that of charge cycles eliminated if you can skip charge days.
FWIW, charge cycles get construed in funny ways, and it tends to mislead folks (myself included). What seems to happen is authors looks for correllaries and come up with things like "charge cycle equivalents". Swell if we're measuring total power available (a watts a watt, and in fairness that's often how the phrase get used), but not so good when the internet thinks it means "hey, I can charge half-way twice and it counts as one charge". That's a "Nope", although if there is a unified way of counting "Charge Cycles" it's been missed by a lot of better minds than mine. My present thinking is a cycle is best thought of as the number of times the battery is charged as this is when its state is altered (what we're counting), heat comes up, voltage comes up to optimum (or not), and etc. I've bumped in articles with DoD and charge cycles analyzed that are only 10% apart, so...
All this suggests if you can put together 2 or 3 days and not charge at all then do that. Don't increase above 70% to get there, and make certain you leave a pretty solid "Oops" buffer. For my use a 20% minimum and 70% gives a 50% operating range between charges.
But we'll see, right? I've other distractions and I'd like do a bit more research hunting, so this may be a few days before I PM you. PM me and bust me if I'm too late.
Note: I did NOT say I'm an SAE engineer doing a study (I've read a few though), a Tesla engineer, or a battery industry insider. When I summarize what I find it will be accompanied by links to all articles and papers used. Take it up with them, I'm just a fancy technical secretary.
Finally, at 120V you may not be able to skip charge days. If not charge to 68-70% as per the display screen, charge nightly, and call it a day.
Here, btw, for those that are of the "franctionalized charge cycles should be added to get 100% DoD" camp, are some links I'm trying to sort out. None seem to agree with that thinking, but I'm aware that's not an uncommon thought here. I'd welcome learned comment w/quality support.
extension://elhekieabhbkpmcefcoobjddigjcaadp/https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=osu1366371336&disposition=inline
extension://elhekieabhbkpmcefcoobjddigjcaadp/https://www.rehab.research.va.gov/jour/90/27/2/pdf/kauzlarich.pdf
Analysis_of_On-Board_Photovoltaics_for_a_Battery_E (1).pdf
extension://elhekieabhbkpmcefcoobjddigjcaadp/https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=osu1366371336&disposition=inline
extension://elhekieabhbkpmcefcoobjddigjcaadp/https://www.rehab.research.va.gov/jour/90/27/2/pdf/kauzlarich.pdf
Analysis_of_On-Board_Photovoltaics_for_a_Battery_E (1).pdf
I’ll stick my nose out.
You will need to do your homework again.
It looks like you did find part of the data on the batteryuniversity. Not everything there is correct.
From the above 3.92V theres only one reference for that; some satellite usage of lithoum ion batteries.
All research tell us a completely different story. The lower the SOC (down to 0%) the lower the calendar aging.
I’m currently the workshop balancing a rotary engine, I will be back withb more info.
You can start searching for Lithium ion + calendar aging, and from the result only selecting research reports (not EV sites, as they often do not know what they are talking about).
You will find data correlating to this:
As per the former post by me.
The lower the SOC, the lower the calendar aging.
The lower the temperature, the lower the calendar aging. At -20C, the calendar aging is virtually not happening. (Theres a lower temperature limit due to the chemistry of the batteries, but it is at 30C somewhere.
The smaller the cycles cycles, the smaller the cyclic aging, also does the region where the cycles is placed matter. The lower the SOC during the cycles the lower the cyclic aging.
“Deep cycle” is a term but the part of the deep cycle causing more degradation is the high SOC part.
Full cycles equivalent (FCE) is the best way to compare different cycle strategies.
FCE will be a direct comparison to how many miles or km a car will be able to do to a fixed degradation level.
We can not on a easy way compare 10% Depth of Discharge (DoD) cycles with 33% or 55% or 70% DoD.
Batteryuniversity.com has at least one chart showing “stress cycles” which does not use FCE (at least per the information, even the research report from which the pucture is taken is unclear on that point.
A stress cycle chart can nit be used to directly compare what is best, as each cycle has a very different energy content.
That chart needs to be converted to FCE to be useful.
Here is a chart on Panasonic 18650 NCA, close to Teslas most used cell chemistry.
The 4.2V chart is cycled 4.2-2.5V, which is 100% DoD. The battery hold up for about 650 cycles at low load (before reaching 80% capacity) also 650 FCE as the DoD is 100%.
The 4.0V chart shows that it holds about 1000 FCE, which is in this case is 1250 cycles (1000/0.8) as 4.0-2.5V is 80% DoD.
We can not directly compare the cycles but the FCE can be compared as one FCE is the same as a 100% DoD.
With 100% cycles a car could hold about 650 x 400* km = 260.000km.
With the 80% DoD we get 1000x400* km, 400.000km.
(400 km is about what we get in true range for a 100-0% drive, in this example).
If we use “cycles” we can not see this correctly in the chart and it is a big chance that we misinterpret the chart, like that chart used in batteryuniverse.com.
Nope, thats not the way to handle cycles.
If you look at charts with FCE you will find that small cycles wear much less than large cycles.
At 10% DoD and low SOC many lithium batteries can do 5000-10000 FCE, thats 50.000 to 100.000 cycles.
This will not cause the lowest degradation.
Read tge above statement about low SOC, low SOC range and small cycles.
There is not danger going below 20% with lithium ion batteries, that part is (also) a myth.
This is a good first read about calendar aging (a short research report)
ShieldSquare Captcha
This is a short report about cyclic aging
https://pdfs.semanticscholar.org/6148/8c8a295061538905ddce0daa877b89c1bcb3.pdf
This is a long research report, covering the most aspects of lithium batteries in electrical vehicles (I recommend this very much, for anyone interrested):
https://mediatum.ub.tum.de/doc/1355829/document.pdf
This is a calendar aging research report of a not named 2170 cell with NCA chemistry.
There is not many manufacturers of 2170 NCA.
https://www.researchgate.net/public...e_Anode-_versus_Cathode-Driven_Side_Reactions
ShieldSquare Captcha
This is a short report about cyclic aging
https://pdfs.semanticscholar.org/6148/8c8a295061538905ddce0daa877b89c1bcb3.pdf
This is a long research report, covering the most aspects of lithium batteries in electrical vehicles (I recommend this very much, for anyone interrested):
https://mediatum.ub.tum.de/doc/1355829/document.pdf
This is a calendar aging research report of a not named 2170 cell with NCA chemistry.
There is not many manufacturers of 2170 NCA.
https://www.researchgate.net/public...e_Anode-_versus_Cathode-Driven_Side_Reactions
My only comment is I'm not sure your 3.92V equalling 70% SOC is correct. I went thru some of my SMT data and here's a couple:
At least for my car 3.944V is 67-68%, implying 3.92V is less than that. I've long assumed 3.92V to be ~63%, but I've never actually documented it. My daily setting goal is 60%, but because of my fat fingers, it's typically 58%. Others have shown that 55% is optimal, but since I started at 58-60%, 3yrs ago, I thought I'd keep it there and see how well it works. As you can see in the image, I'm still at 75.6kWh after 45k miles, so not bad, not bad at all.
The main danger is not to the battery, but to the driver who may not be able to exactly estimate how much the driver needs to reach home or a place to recharge. With the OP's limitation to slow charging (~1kW), it may also be inconvenient to have only a low state-of-charge and then needing to take a longer drive without enough time to charge up to the level needed for the longer drive.
All
Lots of good links above, I'll read them with interest. Thanks for the input!
OP:
Meanwhile, the DoD vs cycles has bothered me no end as there is too many conflicting takes on it. At present I'm inclined to consider the IEEE paper and associated Battery University report (a paper written based on the IEEE research) misleading. This as I've found too many other sources reporting the exact opposite - basically that shallow DoD was preferable. In that this is consistent with Elons stated advice and common lore, well, one has to at least keep an open mind.
Above is as good a single document written in lay language as I've found. It's got a few gaps, but frankly it's better than anything I was writing. It's also clear that shallow DoD is the more beneficial. Very clear. Which BTW supports articles I've seen on wheelchair battery life and solar energy packs.
How to resolve the conflict? Since the BU document is derivative of the IEEE, essentially pointing to one source document, and since I've also found a post arguing their logic was flawed re: DoD and cycles, for the moment I'm thinking the BU/IEEE conclusions are misleading.
Those corrections/perspective corrected, let me say this:
* I've seen nothing leading away me from the 70% is optimal charge level.
* I have seen more data suggesting lower charge rates aren't particularly harmful.
This research suggests there's a hornets nest of opinions, quasi research, and opinion. Large scale data harvesting necessary for real conclusions seems a bit rare, and it's hard to conclude much on a few cases. But of course I've many posts above to read too, so..
YMMV.
Lots of good links above, I'll read them with interest. Thanks for the input!
OP:
Meanwhile, the DoD vs cycles has bothered me no end as there is too many conflicting takes on it. At present I'm inclined to consider the IEEE paper and associated Battery University report (a paper written based on the IEEE research) misleading. This as I've found too many other sources reporting the exact opposite - basically that shallow DoD was preferable. In that this is consistent with Elons stated advice and common lore, well, one has to at least keep an open mind.
Above is as good a single document written in lay language as I've found. It's got a few gaps, but frankly it's better than anything I was writing. It's also clear that shallow DoD is the more beneficial. Very clear. Which BTW supports articles I've seen on wheelchair battery life and solar energy packs.
How to resolve the conflict? Since the BU document is derivative of the IEEE, essentially pointing to one source document, and since I've also found a post arguing their logic was flawed re: DoD and cycles, for the moment I'm thinking the BU/IEEE conclusions are misleading.
Those corrections/perspective corrected, let me say this:
* I've seen nothing leading away me from the 70% is optimal charge level.
* I have seen more data suggesting lower charge rates aren't particularly harmful.
This research suggests there's a hornets nest of opinions, quasi research, and opinion. Large scale data harvesting necessary for real conclusions seems a bit rare, and it's hard to conclude much on a few cases. But of course I've many posts above to read too, so..
YMMV.
Agreed, or so it seem. I've spend a silly amount of hours since. The sad part is the BU articles are based on IEEE paper, and you'd think those guys got it right.
Another problem, and most of your initial graphs show the same problem, is that they're all temperature based. Data on DoD vs cycle is rarer.
I'm not going to reply to each of your posts (probably), but I'm looking at each now.
Thanks for your efforts,
-d
Since we've got some interesting comments flowing:
extension://elhekieabhbkpmcefcoobjddigjcaadp/https://pdfs.semanticscholar.org/6148/8c8a295061538905ddce0daa877b89c1bcb3.pdf
The thought that regen braking is part of cyle aging is intriguing. Now why didn't I think of that? Not anything really new in there otherwise.
Any chance you've got that in English? Being a stupid American I don't read, nor speak, German.
extension://elhekieabhbkpmcefcoobjddigjcaadp/https://pdfs.semanticscholar.org/6148/8c8a295061538905ddce0daa877b89c1bcb3.pdf
The thought that regen braking is part of cyle aging is intriguing. Now why didn't I think of that? Not anything really new in there otherwise.
Any chance you've got that in English? Being a stupid American I don't read, nor speak, German.
Thanks for your comments. Four thoughts:
1) The 3.92V information comes for BU,and well.... However, a source well known for his Tesla battery research also quotes 70%. Tesla battery expert recommends daily charging limit of 70% to optimize durability
Here is the BU quote and table used to get to what 3.92 might look like. Is it right? The entire subject is a darn minefield, it's hard to know. The implication though, is pretty strong - SoC in the 3.9V area is preferable.
"In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms(See BU-808b: What causes Li-ion to die?)
2) Is 3.92 70%? The challenge is knowing what 70% I assume (and we know what that means) said 3.92V must refer to the entire pack, not display capacity post BMS. I thus assumed one had to correct back down to "displayed" capacity, for we know there is hidden/protected range now display/calculated in what we see. Is that true? Dunno. It seems accurate, for if we're seeing conclusions based on what a BMS is showing us, well... variables introduced, right?
If we use some averages and correct for hidden capacity you did get ~ 70%, and since it agrees with the "Tesla" expert I consider it validated. Correct? Dunno. I'm certainly not going to say you're wrong.
3) With respect to your data, one data source is too easy to have the vagaries of individual pack behaviors be all that conclusive, and of course we've got the BMS obfuscating things.
YMMV, but for now I see enough data to suggest 70% is reasonable. Since it more than meets my daily needs I see no reason to push higher. There are those that suggest lower is better. I'm not on board there yet (see the BU notes), but I'm certainly forced to keep challenging the data we see out there.
Thanks,
-d
This seems to conflict with your position, and that of your data, that shallow DoD is preferable. Can't have it both ways, and on the surface that's sort of how the latter reads.
Of course one gets victimized by how others interpret what is said too, so: Are you only trying to suggest that normal cycle behavior is optimized by shallow DoD, but that an occasional trip into deep discharge does no serious harm, and that in fact there is no magic "this will kill the battery" point?
Obviously there is a discharge point of damage, but to my knowledge BMS's block discharge down to these damaging voltages. I also assume the Tesla BMS is doing same, and that displayed range is above such a damaging cut-off point. Likely also part of your thought.
Yes?
I've read many posts over many years on many topics. Of consequence I tend to not listen to folks quoting tribal lore until I've had considerable time to figure out who the thinkers are vs the parrots. That said, pretty solid posts gentlemen. Props and respect.
I'll read a few more articles I want to get to, but at this moment I'm thinking these two links give we layman the best information available for practical use:
Obviously this also means my thinking has had to be reset on DoD vs cycle life. NBD, I learned a long time to be dispassionate about silly things like changing ones mind in the light of new evidence. Amazing how often people defend to the death things though.
Unless I see otherwise I'm unlikely to spend much more time on my white paper. Saft's efforts are just too good save for the gap in optimum SoC. But if two links can deliver the degree of information those do, well.. that's the move.
Thanks again gentlemen, and of course share more as appropriate.
-d
I'll read a few more articles I want to get to, but at this moment I'm thinking these two links give we layman the best information available for practical use:
Obviously this also means my thinking has had to be reset on DoD vs cycle life. NBD, I learned a long time to be dispassionate about silly things like changing ones mind in the light of new evidence. Amazing how often people defend to the death things though.
Unless I see otherwise I'm unlikely to spend much more time on my white paper. Saft's efforts are just too good save for the gap in optimum SoC. But if two links can deliver the degree of information those do, well.. that's the move.
Thanks again gentlemen, and of course share more as appropriate.
-d
Ken, since I''d built the table for my work I'll share it with you:
How you elect to correct for the range 60%-65% is up to you. as I've said, I elected to assume that was of the entire battery pack and need corrected back to usable as shown my the BMS. I could be wrong, but here's the data (from BU) if it helps you.
How you elect to correct for the range 60%-65% is up to you. as I've said, I elected to assume that was of the entire battery pack and need corrected back to usable as shown my the BMS. I could be wrong, but here's the data (from BU) if it helps you.
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