90% the new recommended SOC?

[Olds442]

when i picked up the MS last year, they said to charge to 90% unless going on a trip.

it wasn't until i started reading the internet that 60%-80% SOC came into play.

when i thought i had a degradation issue i was told to cycle it from 5% to 100% and try again, and to regularly charge to 90% and not 60-80%. that charging to a lower SOC than 90% mucked things up with the range. they also said to cycle it at least once a month.

 

[Big Dog]

And when I'm ~15 minutes away from driving, I'll open the app and move the marker to charge to 100%.

Yeah, but then you lose regen so you need to stop the car Fred Flintstone-style (with your feet!).

 

[Jedi2155]

This! While each contributes, combining heat + full charge + time sitting without discharge = very bad times. Each of these has an exponential rate of degradation as they rise, so combined things get bad fast. I've seen elsewhere that for time spent sitting at high charge, the curve tends to start turning the corner around 4hrs.

It's interesting to note:

An interesting discovery was made by NASA in that Li-ion dwelling above 4.10V/cell tend to decompose due to electrolyte oxidation on the cathode, while those charged to lower voltages lose capacity due to the SEI buildup on the anode.

That implies that it is bad to leave car sitting for extended periods below 70% or so charge, getting progressively worse the lower it is (a guess on that optimum SOC, because the 60% they give there won't map to what the car says is 60%, as the designers don't want to take it to true 100% and we know that Tesla's packs don't go all the way to 4.1V when "full").

So I've been researching SEI bulid-up trying to gain an a better understanding of why some battery experts suggest 30-80% rather than 0 to 80% or something of the like. AFAIK, I can't seem to find a source to explain the 30% number (which is ~3.71v). I've talked to multiple battery experts on the matter but not too many electro-chemists and they've all said that the 30% number is simply a safety factor so that the battery doesn't self-discharge below 0% if you happen to store it for too long. Beyond that, I can't find a reason.

This a great paper from some MIT professors that have created a reasonable theoretical model on SEI build up. In it they basically explained the SEI is primarily driven by calendar life (age) rather than cycle life (miles). SEI build up itself is driven the diffusion rate of the electrolyte species which can be described by the Arrhenius equation . To summarize that equation, temperature increases reaction rates. Thus the whole concept of minimizing high temperatures for our batteries to minimizing calendar life aging. Close to 0 degrees Celsius will slow down most of SEI build up but has the negative aspect of killing our power capability, so its a balancing act between increasing reaction rates with higher temperature (more power! ala ludicrous mode) vs. maximizing cell life with minimizing temperature.

 

[JRP3]

As for batteries not self-discharging, I’m not sure where you got that information, but it’s not correct

If the discharge rate is measured in years it's not relevant.

 

[cdeleo]

Wow I was all ready for this thread to go to /dev/null but I guess not. Thanks everyone for the information. I've bumped my charging from 70% to 80%. I do agree that it seems odd that Tesla doesn't do some of these 5min. feature additions that I see all over the place people requesting. I'm still waiting for them to add the ability to start stop and start again charging for different times. This is the main reason why I'm charging to 80%, if they add in the ability to start charging again I would charge to 80% when I first get home from work. Then at about an hour before I leave I would start charging again to warm the battery for regen in the winter. I would think this would put me close to the 90%.

I know there are other apps out there that can do this but I'm still hesitant about giving my tesla username and password to a 3rd. party. I also know that you can generate a token but I haven't spent the time doing that yet.

 

[CrazyCoconut]

Another factor is that the lower the SOC, the lower the hp/tq. So if you paid for a Performance model, might as well get the most performance out of it

 

[uclabruin11]

Hi everyone -- new to the forums, and new to owning a Tesla, as I just received my Model 3 yesterday after almost three years of waiting (and many, many more years of saving). It's amazing, to say the least.

Great topic and been doing my best to educate myself. I know it's all subjective -- and I generally abide by the idea that it makes the most sense to balance between general battery care and enjoyment of the car -- but wondering what each of your varying opinions about those of us who cannot charge daily/plug in. (Yes, I have RTFM that it is best to stay plugged in, but again, it's not an option. We do have a single car garage, but no outlet to plug in.)

There are a million public chargers and superchargers in the Los Angeles area, plus both my parents and brother have wall chargers, so we have no issue with getting charges when we need it -- plus I have a short daily commute. I plan on having this car for at least 10 years, maybe more. You guys all think I should try to do make extra efforts to do shallow charging during the week occasionally instead of charging to 80/90% and driving my battery down to maybe 25-30% or so, before having to charge again? Obviously the latter is more convenient, but because of my situation, that will be a lot of cycles and do want to keep my battery in generally good condition. Or, does it all just not matter...as some folks are saying.

Thanks in advance!

 

[TexasEV]

You guys all think I should try to do make extra efforts to do shallow charging during the week occasionally instead of charging to 80/90% and driving my battery down to maybe 25-30% or so, before having to charge again? Obviously the latter is more convenient, but because of my situation, that will be a lot of cycles and do want to keep my battery in generally good condition. Or, does it all just not matter...as some folks are saying.

That’s not a cycle. A cycle is 0 to 100%.

 

[uclabruin11]

That’s not a cycle. A cycle is 0 to 100%.

Yes, okay, that's true -- but you know what I mean. Say, an almost-cycle from 90% to 10% (or whatever I feel comfortable with for my short commute). The point is, is that I'm not plugging in anyway, I will go through these almost-cycle charges. I was just wondering your thoughts on battery health without the ability to plug-in daily/nightly.

 

[jjrandorin]

Yes, okay, that's true -- but you know what I mean. Say, an almost-cycle from 90% to 10% (or whatever I feel comfortable with for my short commute). The point is, is that I'm not plugging in anyway, I will go through these almost-cycle charges. I was just wondering your thoughts on battery health without the ability to plug-in daily/nightly.

I would charge however is convenient for you between 30% and 90%, knowing that you have an 8 year warranty on the battery to either 100k or 120k miles depending on which model 3 you have, and also knowing that the replacement for a battery pack for these cars is less than an engine replacement for a performance car. The battery replacement cost will get cheaper as the batteries improve, as well.

So, charge it when you want to without worrying about it from 20-30% to 80-90% and either get it swapped out under warranty if you have less than 70% SOC left during the warranty, or save all the money you are not spending on oil changes / transmission flushes etc for the next 8 years 100k miles until you are out of warranty and replace the battery then.


Thats my opinion, and I am also a new Tesla owner (but I can plug in every night.. but I dont think it matters too much over the time we will own the car, and if so, I will either get the battery replaced under warranty, or pay for it to be replaced.)

 

[JRP3]

I have a short daily commute.

Let's say you average 20 miles a day, 7,300 a year, after 10 years that's only 73,000 miles, 20 years 146,000 miles. I don't think it matters what you do the pack would probably age out before it cycles out.

 

[uclabruin11]

Thanks to you both -- this all makes sense and is good advice. My wife has had a Chevy Bolt for over a year, leased of course, and we just charge it all the way to 100% and never care because it's not ours, and don't think twice. Although it could change the down the road, yes, I won't drive 8K miles this year, and just assumed the Tesla's will handle anything I put on it without worrying about it too much (within general rules, of course). But, then in these forums and elsewhere, there is so much talk -- understandably -- about battery care, and perhaps need to put a bit more thought into it considering my situation. I could have a far commute 5 years from now, so want to be prudish, but will just be sensible and assume my pack will be fine.

 

[tga]

leased of course, and we just charge it all the way to 100% and never care because it's not ours,

<RANT>As the owner of a used EV, it drives me nuts to read these kind of statements. "Screw the next guy, I'm gonna go out of my way to abuse the battery, for no reason other than it's not my problem." If you don't have to charge to 100%, why do it?</RANT>

 

[CrazyCoconut]

<RANT>As the owner of a used EV, it drives me nuts to read these kind of statements. "Screw the next guy, I'm gonna go out of my way to abuse the battery, for no reason other than it's not my problem." If you don't have to charge to 100%, why do it?</RANT>

At the end of the usual lease length (3 yrs / 36k miles), even if you frequently charge to 100%, the degradation will be very minor, if not negligible.

 

[jjrandorin]

<RANT>As the owner of a used EV, it drives me nuts to read these kind of statements. "Screw the next guy, I'm gonna go out of my way to abuse the battery, for no reason other than it's not my problem." If you don't have to charge to 100%, why do it?</RANT>

This is not an EV thing, but I am sure you know that. I leased my BMWs and took care of them like they were mine, but many (MANY MANY) others not only didnt take care of them, but actually "abused" them by putting after market boost chips in them, etc, and simply removed them before lease turn in.

I know this is a tesla forum, but if anyone is ever considering a used BMW / Mercedes / Audi etc, get a pre purchase inspection, no matter if you are buying it from the brand dealer CPO or not.

 

[JRP3]

At the end of the usual lease length (3 yrs / 36k miles), even if you frequently charge to 100%, the degradation will be very minor, if not negligible.

Depends. If it's regularly charged to 100% and left to sit at full charge for hours, especially in the heat, that might cause accelerated degradation.

 

[uclabruin11]

Let me rephrase this: we don't deliberately destroy or degrade anything. We take excellent care of our car.

1) It's our first EV and yes, we charge to 100% -- particularly because since we can't plug in at home -- we need to get as much charge as we can. We leased the car so we can drive the car and use it for it's full capacity. The dealer will be lucky to get a car back leased, in perfect condition, driving 6,500 miles per year.

2) Unlike Tesla, Chevy -- and again, we love our car and it's a fantastic car -- says nothing of the sort. Our dealer, even in Southern California, knew nothing about our EV and just said congrats, and off we go. We had zero idea about the whole SoC thing when we got it. If Chevy really cared about their EV's, they need to actually tell buyers how to work and take care of it. It was only until I started reading more about battery care through my interest in Tesla and research prior to buying my car that I realized this was a "thing" anyway.

I think #2 is partially why GM is trying to restructure (VW, too, for that matter, recently) -- they need to re-think their infrastructure and approach to EV's and the future. The Chevy Bolt, for those of you who have never driven it, is an amazing car. It's an unbelievable accomplishment from GM. It's truly an amazing car. (Obviously, no comparison to Tesla, but comparison to the general market of non-Teslas.) The fact that it has so little advertising, not the crown jewel of Chevy -- in my opinion -- is a crime and that speaks to how you walk into a dealership and EV's are an afterthought or salespeople have little knowledge of them.

 

[saltsman]

Thanks to you both -- this all makes sense and is good advice. My wife has had a Chevy Bolt for over a year, leased of course, and we just charge it all the way to 100% and never care because it's not ours, and don't think twice. Although it could change the down the road, yes, I won't drive 8K miles this year, and just assumed the Tesla's will handle anything I put on it without worrying about it too much (within general rules, of course). But, then in these forums and elsewhere, there is so much talk -- understandably -- about battery care, and perhaps need to put a bit more thought into it considering my situation. I could have a far commute 5 years from now, so want to be prudish, but will just be sensible and assume my pack will be fine.

For whatever it's worth, this is the ideal way to charge a Chevy Bolt. GM restricts the battery from charging to a full 100%, just like it prevents the battery from going all the way down to zero. When the Bolt display says 100% full is battery is actually 96.5%. When the Bolt display says 0% the battery is actually at 9%.

And, just like the TM3, you want to keep the Bolt plugged in whenever possible. Keeping it attached to shore power allows the battery temps to be better managed and allows for vampire drain to be siphoned from the charger directly rather than the battery - thus minimizing battery cycling (even if it's only minuscule).

I've been doing the EV thing for about four years now and the one consistent I've seen across all brands is that EVs bring out the OCDs ;-)

 

[tga]

Let me rephrase this: we don't deliberately destroy or degrade anything. We take excellent care of our car.

To be clear, I wasn't intending to single you out personally. I was just ranting in general.

This is not an EV thing, but I am sure you know that. I leased my BMWs and took care of them like they were mine, but many (MANY MANY) others not only didnt take care of them, but actually "abused" them by putting after market boost chips in them, etc, and simply removed them before lease turn in.

I know this is a tesla forum, but if anyone is ever considering a used BMW / Mercedes / Audi etc, get a pre purchase inspection, no matter if you are buying it from the brand dealer CPO or not.

I know, but most cases I can think of for ICE car abuse have some positive value. People skip service on leased ICE's that are "some else's car" to save money. They do chips, exhaust, suspension, etc to improve performance. But charging to 100% just because you can doesn't really have much return for the abuse.

Depends. If it's regularly charged to 100% and left to sit at full charge for hours, especially in the heat, that might cause accelerated degradation.

This. I frequently charge to 100% for trips. I charge to 90% overnight, and then bump it up to 100% 2 hours before departure. Or I figure out when to start charging to finish at 100% right before leaving. At 68K miles, I have ~3.5% degradation (256 miles @ 100% vs 265 new). The key thing is it doesn't sit at 100% for long. I also try to stay above 20%. I think I've gone below 10% maybe twice in the last 40k miles. Sometimes that means an extra 5 minutes at a supercharger to add a little more buffer.

 

[JRP3]

Keeping it attached to shore power allows the battery temps to be better managed and allows for vampire drain to be siphoned from the charger directly rather than the battery - thus minimizing battery cycling (even if it's only minuscule).

Power flow is from the plug to the charger, then to the pack, then to the dc/dc, then to 12v loads. The main pack is still in the loop.