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Charging for optimum battery life

Charging for optimum battery life

Lets say I drive 50 miles every day.
Is the best charging strategy (for long term battery health) to charge to 150 miles rated every night?
Or is it better to charge higher and run a few days before charging again?
Is it ok to keep the battery charge around its midpoint or does it help to let it go higher or lower once in a while?
Thanks

SCCRENDO | 22 July 2014

Optimum state of charge is 50-62%. Charge as much as you need but try not to go above 90% if you don't need to. Always keep your car plugged in.

J.T. | 23 July 2014

@msstrong Perhaps you should take a little time and read through the TIPS, TRICKS AND TROUBLESHOOTING Thread. This plus a whole bunch of other useful information is there.

Anthony J. Parisio | 23 July 2014

mstrong72,

I read 80% is optimum for lithium batteries in use. While 50% is optimum for long term non use. That is only about any lithium batteries not a Model S. Tesla recommends leaving the car plugged in when not in use. This is not because of charge so much but rather to keep batteries cooled or warmed. This may extend their life for many many years.

It is still OK to not plug in for several days even a couple of weeks. However, the car dose use charge to keep things in shape as it sit. If it sit to long it will go into deep sleep to minimize this power drain. You can set when this should happen. You should read about "deep sleep" in the manual if you need to leave it at an airport for a couple of weeks.

I hope this helped.

BrassGuy | 23 July 2014

Since around 50% is optimum for long term, for a daily 50 miles probably 150 miles charge is best. For an 85kWh, 265/2+50/2=157.5. If you may have unanticipated driving, keep it a little higher. I usually use %70 and up the charge before a high mileage day.

I'm also under the impression that it's good once in a while to utilize more (not 100%) of the battery, but I don't remember where I read that. It was about batteries, not about refreshing the rated miles calculation.

Really though, just enjoy the car and let it take care of itself. If you don't range charge daily, you're probably good for many years.

ChasF | 23 July 2014

If you're really anal and want to hit the 50%-62% range exactly, you would also have to factor in the hidden reserve capacity of the battery (see Rod and Barbara's thread) to determine the true midpoint. Not that it makes a significant difference.

J.T. | 23 July 2014

Not that it makes a significant difference.

Once we can all accept this mindset we'll all feel a lot better.

johncrab | 23 July 2014

We are talking about a car that had a lot of thought go into it. While it is good occasionally to push the battery outside its sweet spot gently and for short periods, the best advice comes from the manual which says to leave it plugged in. The car will manage the battery on its own. I'm a tinkerer and I honestly cannot find any quarrel with Tesla's thinking on this subject. Push the charge level up once a month or so but never to 100% and then get it back off that level quickly and resume normal use.

Other good advice comes from the ICE mentality. Run in the tires, motor and brake linings entry with any new car or new tires. Avoid demanding situations for the first 100-200 miles. This includes the battery. Don't make wild demands of it right away. Yeah, I know. It's kind of hard to be that disciplined but with a proper "running in" as the Brits say, things work better over the long term, especially tires.

BrassGuy | 23 July 2014

Aw not again! "...never to 100%..." Don't scare people away from a range charge. Just don't charge to 100% and abandon it for a week. If you meant periodically charge to 90% if you don't normally, I can see that. And I'm pretty sure there's not a break-in period for the battery like there is for an ICE. No piston rings or valve seats. Just go.

jordanrichard | 23 July 2014

Since no one here presumably works for Tesla, is not an expert of batteries in the manner which they are used in the MS, then these are just opinions based on.......

Look at the charging screen in the car. Tesla considers 50-90% charge as being "Daily" and anything higher as "Trip". Tesla also states to not leave the battery sitting at a high state of charge which is 100%. If you charge to 100%, be sure to be on your way and let some of that charge "burn off".

If Tesla thought 90% daily charge was detrimental to the battery, they wouldn't place it in the "Daily" range. If they were concerned about it, they would have changed it. For those with the Pano roof, you may have noticed that Tesla now sets the "comfort" setting as 75% open vs the previous 80%.

My point is that if there was a problem with people charging to 90% on a daily basis, again they would have made a change.

The problem with the internet is once an opinion gets out there and kicked around enough, people start accepting it as fact.

omarsultan.ca.us | 23 July 2014

Disclosure: I am from the non-coddling camp of battery care. I just posted my 1 year/29K mile results in another thread. The short version is that I 90% charge daily and max charge and SC at least once a week. After a year, I have maybe lost 2-3 miles of rated range against the benchmark 265 number.

@BrassGuy is right - if you need the range for a trip, max charge then make the trip.

One of the more interesting sessions at TMC:Connect last Saturday was one by Tom Saxton of Plug-In America who has been doing longitudinal survey of battery pack life in EVs (MS, Tesla, Leafs). His assertion is that primary factor in pack degradation is the number of full cycles the pack has gone through. BTW, I highly encourage you to take the survey (it takes a coupe of min), since the more data points he gets, the more accurate the projections: http://www.pluginamerica.org/surveys/batteries/

O

renwo S alset | 23 July 2014

Keeping plugged in when not in use begs the question; if you have it scheduled for charging during "off-peak" usage rates, then you are not getting any benefit from having it plugged in when not in use (during no peak hours). I solved this by simply disabling "scheduled charging". However, I am paying a premium for that battery care.

NKYTA | 23 July 2014

@O, agreed, good data. Though the fact that Tom isn't factoring in software version changes makes me think there is probably some noise in the graphs (but slight).

jordanrichard | 23 July 2014

Another fact to keep in mind that a "full cycle" is a battery going from completely empty to fully charged back to empty.

So when someone says a battery can handle "X" of cycles, being equivalent to "X" miles, then know that your battery will last longer because it's highly doubtful that anyone is actually running their battery through a full cycle.

carlk | 23 July 2014

I've heard quotes from Telsa people, one I believe from Elon himself, that keeping the charge state at between 40%~80% or 30%~70% is the best for battery life. My rule is try to manage the use and charge so the battery is always as close to 50% charged, on the road or sitting in the garage, as possible but free to make it on the high side so to avoid any possible range anxieties. That's just a general rule but don't need to be followed to the letter.

As some have mentioned the time that the battery is at nearly fully charged or close to empty state is most important. Drive off right away soon as you have range charged and plug it in whenever the battery is very low should be practiced.

JAD | 23 July 2014

Keep in mind, there are virtually ZERO real world long term tests of any of these theories. They don't have a sample of 10,000 who charge 50%, 10,000 who charge 80%, 10,000 who charge 100% for 5 years to really know if it makes a difference and if so, how much. The few data points we have show the battery lasts a long time. I have seen ZERO cases of significant battery degradation in any post under any use pattern.

Follow Tesla's recommendation and just enjoy the car. Maybe in 5-10 years we will have the real answer, not just informed (or random) guesses based on sorta similar batteries in completely different uses.

SCCRENDO | 23 July 2014

Anyone here see Tom's results plotted out?

AmpedRealtor | 23 July 2014

@ jordanrichard,

No, this is not idle speculation or opinion. I was specifically told by Ownership during a phone call shortly after I took delivery advising me to keep the battery at a 50%-62% state of charge. I was told that is the best charge level in order to minimize degradation, but that the difference between 50% and 90% is "negligible".

Tesla made a conscious decision to keep the charging side of things simple for owners, which is as it should be. But those for those of us who want more granular control, and who want to minimize degradation as much as possible - even if it's "negligible" - Tesla offers the 50%-62% advice. I also told them that I will typically drive my car once every few days, not every day. Intuitively it doesn't make much sense to keep my battery at 80% charge if I'm not going to drive it a few days. It makes more sense to keep it at 50% and then charge up before an outing.

I offered the same information about a year ago here at TM Forums. Owners jumped on me, telling me that even Tesla doesn't know what it's talking about and that 90% is just fine. Yet since then, Tesla has seen fit to introduce a variable slider to give owners granular control. If it made no difference, can you tell me why Tesla would offer owners the option to charge to only 50%? Previously, Tesla only had two options - standard charge (90%) and range charge (100%).

I believe Tesla has learned a lot in the last 18 months, one of which is that a lower SOC is better for the longevity of the battery, hence the introduction of a sliding control.

jai9001 | 23 July 2014

My real world experience is that owners who truly use their batteries more aggressively have seen less battery degradation.

I religiously followed the advice to keep my battery between 50-70% for an entire year and never performed a range charge.

I have seen above average battery degradation to this point.

carlk | 23 July 2014

AmpedRealtor and jai9001 are right. Tesla has tons of data of how the batteries behave. After all this IS their business. They are only trying to make it simple for owners and not to risk of having any mishaps caused by low battery, not everyone is so technical minded, so there was this simple plug it in all time and charge up to 90% or 80% advice. It probably won't make a world of difference but you should follow Tesla's (unofficial ~40%~70%) guide if you really want to squzee every bit of battery life possible out of yours.

Bighorn | 23 July 2014

At my recent annual service, the SC manager told me that they've found that people who rode hard and put away wet were having fewer problems than those who are babying their cars. I'd heard similar sentiments about how the loaners that were getting lots of use and range charges seemed to be showing better numbers. Of course, this could be an artifact of use that will prove unsustainable in the long run. Best not to worry, but that's not an option for some.

AmpedRealtor | 23 July 2014

@ jai9001,

I have seen above average battery degradation to this point.

You have not seen any degradation. What you are seeing is a reduction in your range estimate, which drifts lower over time. The Model S range algorithm only knows the true limits of the battery when it charges to 100% and then discharges to zero. Unless you've done that, your range algorithm can only guess at the upper and lower limits.

For instance, in my case a 50% charge gives 144 miles of ideal range. Does that mean at 100% I'm only getting 288 miles and that I've suffered 12 miles of degradation? Not at all. When I charge to 100%, I get 301 miles of ideal range.

jordanrichard | 23 July 2014

I certainly didn't mean to offend or question the advice from those who have had their cars longer than I.

Though I certainly don't need 238 rated miles (90%), on a daily basis, I like the comfort knowing that if I needed to I could drive out of state and back. I live in Northern CT and presently there are no Superchargers North, East or West of me. The nearest SC is 65 miles South of me.

jai9001 | 23 July 2014

AR,

I think you are correct in some cases, but clearly not all.

I had specific engineering review of my battery and was told that I had some battery degradation. This review was prompted by the fact that as part of the annual maintenance they perform a range charge.

I was told that a specific "cluster" was not fully charging.

In order to determine if that cluster was out of balance or prematurely degraded, I was asked to range charge daily for 6 days and then cycle the battery from 25% to 90% for one month and then range charge again.

Before the experiment, my range charge was 245/286 rated/ideal miles of range and after it was 253/293 miles. I was then informed by engineer that this was an average amount of degradation for a one year old care with 13000miles on it.

I was also told to charge the car to 80% daily and to cycle the battery and range charge every other month.

AmpedRealtor | 23 July 2014

@ jai9001,

Got it, sorry. I remember reading about your particular issue, but I didn't associate it with your screen name. Is it your feeling that babying the battery caused the failure of a cell cluster, or that it was unrelated?

I sort of wish that Tesla had provided us with a 100 kWh battery, software limited to 85 kWh. That way, when the battery finally did start to degrade, additional capacity would be transparently made available so that the consumer never experienced any range degradation. In other words, give us an extra 20% degradation buffer above 100% charge that can be tapped when degradation sets in.

nickjhowe | 23 July 2014

From what I recall from Tom Saxton's presentation last Saturday at TMC connect, the single biggest factor that affects capacity is not age, nor distance, nor temperature, but cycles.

So...multiply lifetime distance traveled * average kWh/mile / pack size in kW = an approximation of # of pack cycles. The higher the number, the bigger the degradation. Hopefully Tom will publish the graphs soon.

So... I have 12000 miles at 0.320 kWh/m and an 85kWh pack = 45 equivalent cycles - with virtually no degradation in my range charge distance.

90000 miles at 400 Wh/m in a 60 kWh pack would be 600 equivalent cycles - and one would expect to see very measurable degradation in max range.

jai9001 | 23 July 2014

AR, Nickjhowe,

Any thoughts on the discrepancy between amount of degradation seen between rated and ideal?

Ideal degradation 300-293/300 = 2.3% Not bad in my opinion.

Rated degradation 265-253/265 = 4.5% meh!

I still think that the battery is out of balance and by cycling the battery every two months I might continue to see some improvements.

mrspaghetti | 23 July 2014

One of the (many) reasons I want a Model S is that you could apply the old Geico slogan to the charging procedure: "So simple, even a caveman could do it."

[No offense to any cavemen on this forum.]

omarsultan.ca.us | 23 July 2014

@SCCRENDO:

Yes, he presented findings at TMC:Connect last weekend. I'll see if he is willing to post slides somewhere.

O

jordanrichard | 23 July 2014

So if it is known how to calculate a cycle, is there a know or general consensus of how many cycles the battery pack is rated for or predicted to handle?

Though I guess it all depends at what point one considers the battery to be at the end of its usefulness.

BTA22 | 23 July 2014

Tesla told me to charge to 90% and always plug it in. That's what I do. They have an army of brilliant engineers that are paid very well to "not screw this up".

I also find it ironic that those so concerned about degradation - and reduced range - are willing to self-prescribe reduced range every, single, day...by half-charging.

Life is short, when you're born you start dying, so loosen up and enjoy it.

carlk | 23 July 2014

Looks caveman did post. ;-)

tes-s | 23 July 2014

I do what is convenient, and just avoid the endpoints when possible. I generally keep it between 50 and 230 rated miles, but I don't hesitate to do a range charge if I need it, or drive it to 0 if I have to.

tes-s | 23 July 2014

...and I ALWAYS avoid leaving it very long at more than 230 miles without driving, and less than 50 without charging.

J.T. | 23 July 2014

@BTA22 You said Tesla told you to charge to 90%. Who at Tesla? Because for every person who tells you that we can find a different Tesla person to say 50-70%.

I also find it ironic that those so concerned about degradation - and reduced range - are willing to self-prescribe reduced range every, single, day...by half-charging.

Not self-prescribed, Elon prescribed.

renwo S alset | 23 July 2014

I only self-prescribe my own meds.

AmpedRealtor | 23 July 2014

@ BTA22,

I also find it ironic that those so concerned about degradation - and reduced range - are willing to self-prescribe reduced range every, single, day...by half-charging.

Life is short, when you're born you start dying, so loosen up and enjoy it.

What would be the benefit of keeping the battery charged up when I'm only driving the car every few days? Avoiding extremes in any situation is usually the prudent thing to do. Based upon my driving patterns, keeping the car charged at 50% gives me peace of mind regarding battery longevity combined with being more than enough for my daily usage. I have a 80A HPWC. On days when I have appointments I can add the additional range in no time at all.

jai9001 | 23 July 2014

I agree with AR.

If you don't spend a lot of time in your car and you live in a city with a short commute, how much should you charge your car to?

I drive no more than 50 miles/day.

I work 5 miles from my home.

Once a month I drive to an office 50 miles away.

I never experience traffic.

I never have range anxiety.

My car has never had less than 50 miles of range.

I think my pattern would be different if I had a long commute, had to worry about errands, and lived in a city with lots of traffic.

Captain_Zap | 23 July 2014

@JT

Before we were able to select our own preferred state of charge, there was only two charge settings. A "standard charge" was 93% and a "trip charge" was 100%

BTA22 | 23 July 2014

@Jai - buy a Leaf

All these armchair battery experts, yet no links to back it up. When did anyone say to charge this engineering marvel to 52%? Show me the link!

And for Pete's sake, if the difference between charging to 50 and 90 is "negligible" (earlier post), why are we all so suddenly wound so tight on preserving a sliver of battery life? Half of you big shots just paid an extra $13k so you could shave .8 seconds off you 0-60 time (P85 from 85), yet you drive your car to the grocery store and back all of 4 times a week based on these posts.

Which is it? Are we wound up so tight on this purchase that we can't fathom a "negligible" battery degradation over many years? Or are we tossing around a couple semester's room and board to get the P85 so we can say we can beat a Porsche "between those two stop signs".

90% charge every damn night!

carlk | 23 July 2014

Caveman thinking alright.

BTA22 | 23 July 2014

Sources, Carl, sources. Show me print from Tesla that says to charge to 50%.

jai9001 | 23 July 2014

BTA22,

Your post has so many ridiculous assumptions.

You assume the only reason many of us bought a model s is for the range.

Performance, aesthetics, comfort matter.

You make it sound like setting the charging slider to 60% is hard work and something I think about a lot.

I actually feel bad for some of you who live in cities with tons of traffic and long commutes. Definitely reduces quality of life.

On the other hand, if I had a long commute I'd want to do it in a Tesla.

SCCRENDO | 23 July 2014

A lot of mental masturbation going on here. I am a at 40500 miles in just over 16 months. I have no serious idea as to the state of my battery because of the multiple firmware updates that we have had. I know for sure that I have lost nothing since Oct last year at 12000 miles. At most I could be down 3%. I charge most days 80 or 90 % and range charge when needed. My max charge is consistently 252 miles rated, 292 ideal. I drive too much to worry.

Brian H | 24 July 2014

Negligible means you can neglect it (and would be hard pressed to measure it). Much ado about nuttin' much.

J.T. | 24 July 2014

@BTA22 Sources, Carl, sources. Show me print from Tesla that says to charge to 50%.

The manual says to charge from 50% to 90% depending on daily needs. Page 87.

J.T. | 24 July 2014

@Zap Glad we're out of the dark ages.:-) Anyway, I believe it was at Teslive that Elon used the 30% to 70% range. I could be mistaken.

bp | 24 July 2014

The current User Guide states "For daily driving, charge between 50% and 90% to improve battery longevity. Charge above 90% for trips requiring maximum range."

Until Tesla provides something in writing, this appears to be the only official statement from Tesla on charging.

While there may be some benefit in charging at lower levels, the unofficial statements from Tesla haven't indicated any significant benefits.

I charge to 90% overnight, and haven't had any range anxiety for daily planned and unplanned trips - and haven't noticed any degradation in range.

Keep it simple - charge enough overnight (50-90%) to ensure you have sufficient range for your driving (without allowing the charge level to get too low) - and enjoy the drive past the gas stations and not having to pay $75-100 to "fill up the tank"...

Pungoteague_Dave | 24 July 2014

It isn't written but there IS video of Elon Musk saying that maintaining 50%-60% SOC charge is ideal for battery longevity. I personally maintain at 90% and must range charge twice weekly. We have full cycled full to empty many times on road trips and do that twice per week driving between homes that are 190 miles apart. In winter driving we often arrive with only a few miles range remaining (we drive with the energy screen set to ensure we control speed to ensure arrival, even if requiring us to drive 50 in a 65 speed zone). VIN 4061, 24k miles, no apparent range reduction, although main battery was replaced at about 8k.

jordanrichard | 24 July 2014

Perhaps Elon was referring to what AR is talking about and that is what SOC to have the battery at for a bare minimum. AR apparently doesn't drive his car that often and having his car sit at even 80% is too much, hence the advice to kick it down a notch or two. That is perfectly fine. For those of us that use the car on a daily basis, our cars aren't sitting at 90% for very long.

This argument is like comparing insurance rates, way too many variables.

As I mentioned in a previous post, if Tesla felt that 90% was too high, they would have changed the charging screen to relabeled anything above 80-90% as "Trip".

AmpedRealtor | 24 July 2014

@ BTA22,

I received my information directly from Tesla Ownership. There is no reason for you to be combative, do what you want. Nobody is telling you what to do! lol... what a ridiculous thing to argue about.

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