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Should I charge to 90% every night?

Should I charge to 90% every night?

Sorry if this has been discussed before, but should I be charging my battery to a full 90% every night, such that I wake up every day fully charged? Or should I manually set it to 50% if I know that I'm not going to burn through the full 90% charged battery in a given week?

jlocke | 11 août 2015

I discussed this with a couple Tesla Employees and they said to charge it to 90%. Basically if your not driving it plug it in and let it manage itself.

I asked the question about 50% to 90% and any differences and they recommended to just leave it at 90% unless going on a long trip then to go for 100%

TeslaTwo | 11 août 2015

I plug in anytime I'm home. Don't overthink it. Leaving your home with 50% charge is babying a car that doesn't need to be babied.

TomServo | 11 août 2015

As an outsider isn't this specifically addressed in the Owners Manual?

johngratcliff | 11 août 2015

For most of the two years I have had my P85 I charged to 100% before and during a trip, but when not traveling I charged to the 1st mark short of 100% almost every day (85-90%). Over time I noticed my estimated range began to degrade. Not much but by a few miles. Recently I have changed my charging when not traveling. As I understand it, the fewer charge-discharge cycles the better for the battery. So now, I charge to the 1st mark then do not charge again until the estimated range gets near 100 miles. As a result, when not traveling I do not charge every day. Now the estimated range, whether I charge to the 1st mark or to 100%, is back up to what it had been when I first got the car, on occasion a mile or two better. Just reporting. I would be interested to hear similar or contradictory experiences.

Tropopause | 11 août 2015

TomServo- From the Owner's Manual:

You can charge to any level from 50% to 100%
based on your driving needs.

Pettifogger.ca.us | 11 août 2015

OK,so if there's even the slightest chance that daily 90% charges will eventually decrease battery capacity, and an 80% charge will amply meet your daily commute need, is there any particular reason to charge to 90% (or more) for daily commuting? My wife, the primary driver of our car, has a round-trip commute of 20 miles. She doesn't get any particular charge (so to speak) from seeing 240 miles estimated range in the morning instead of 208.

GAGSTESLA | 11 août 2015

Charge to 90% and not worry about it. Charge to 100% right before a trip and not worry about it. That way, if you have to make an unexpected drive somewhere, you will not be stuck without enough charge. No worries for me for over a year and 35,000+ miles.

Duma | 11 août 2015

@TomServo in a word, the manual does not discuss the optimal nightly "top off" percentage.

The extensive charging discussion in the manual is primarily around ensuring the battery stays adequately charged. The "plug in when not in use guidance" is specifically in the context of not using the car for a period of weeks or longer. Likewise, cautions about leaving the car with less than 10% charge for any period of time. Surprisingly, there is not even mention of only charging to 100% when needed for a longer trip and otherwise staying below 90%.

I expect that many of us overthink this, especially if we come from an engineering background, and will get a small benefit for our effort(extend battery life by a few per cent). The guidance from the service center is likely sufficient for most use.

The main point is that battery is not a gas tank that you fill up and ignore until you have less than 1/4 tank. Since most charge at home or work, charging daily or almost daily is no extra effort and you will have sufficient charge when you need it. Unless you live (or work) near a supercharger, having a lower amount of charge than you need for an unplanned trip could result in an inconvenience.

J.T. | 11 août 2015

@Duma The "plug in when not in use guidance" is specifically in the context of not using the car for a period of weeks or longer.

Where did you get that information? Page 115 of the Owners Manual says this:

Caution: Tesla strongly recommends leaving Model S plugged in when not in use. This maintains the Battery at the optimum level of charge.

This stuff is confusing enough to the newly initiated, let's not make it worse by contradicting stated Tesla guidelines.

teslagiddy | 11 août 2015

I think the answer to the question: "should I charge my Tesla to X percent every night?" is yes, provided that X is any number less than 91. I charge to 80% daily giving me 210 range even though I typically drive about 100 miles a day, that way I'm covered for unexpected errands.

Haggy | 11 août 2015

@TomServo The car and the app make it clear enough by essentially pointing to the 90% and indicating that from there and below is for a "daily" charge and above that up to 100% is for "trip".

The part below 90% is shown as a range, but the notion is that you should not normally exceed the range. Since 90% isn't exceeding the range that Tesla says is safe for daily use and not in any way harmful, it agrees with what Tesla will tell owners who ask.

The point of the range is that you don't want to keep your battery near empty on a regular basis, but won't always have time to charge to 90%.

Duma | 11 août 2015

@lecompte - As I understand science, Li-ion batteries basically have normal degradation when they spend most of their time between 20% and 80% charge. Degradation accelerates when the battery is left below 10% or above 90% for extended periods of time, due to parasitic reactions in the electrodes. Moreover, Li-ion batteries don't have a memory effect, so the size of the discharge cycle within the 20%-80% window does not significantly affect the battery degradation rate.

That said, the rest depends on your driving patterns. If there is a reasonably likelihood that you may need about 70% on any given day, aside from occasional longer trips out of town, then 90% makes sense, since this keeps you above 20% worst case. If 60% is enough, then 80% may be a little better for your battery, but it is not a big deal. If you need 100% or dip below 10% occasionally for a longer trip, that is also fine.

sheldon17 | 11 août 2015

According to this there is some benefit to keeping a lower daily charge limit.

https://mobile.twitter.com/elonmusk/status/448466037441179649

PhillyGal | 11 août 2015

If the question is whether you should exceed 90% on a daily/regular/non-trip basis, the answer is a clear no.

If the question is whether you are required to plug in your car every single night even if you only drive a few miles, my humble opinion is that you don't. A happy car is a plugged in car, or so I've heard many times but we drive so few miles on a typical week day (under 40) that we find charging every other day to be more than enough.

In other words, when not on long trips, our car's battery is almost always between 60-90% and that has worked great for us in these first 8 months.

Duma | 11 août 2015

@J.T. My information is from Model S Owners Manual (North America) dated 3/31/2015, the latest version available to me for download on "MyTesla", page 113:

About the Battery
Model S has one of the most sophisticated
battery systems in the world. The most
important way to preserve the Battery is to
LEAVE YOUR MODEL S PLUGGED IN when
you are not using it. This is particularly
important if you are not planning to drive
Model S for several weeks. When plugged in,
Model S wakes up when needed to
automatically maintain a charge level that
maximizes the lifetime of the Battery.

I italicized the sentence which was the basis for my remark. The next section talks about the risks associated with low levels of charge, especially below 5%.

carlk | 11 août 2015

I charge every night to 70%. I use about 30% of charge for my daily communte plus running errands. The goal is to keep average charge state at ~50%. Don't know if it's necessary but it shouldn't hurt.

I do charge up to 90% or 100% in some weekend morngings when I anticipate longer trip that day. As others have mentioned drive off soon as the car reached full charge. Don't let it sit there that way overnight.

buickguy | 11 août 2015

My work sometimes requires about a 200 mile day, so I charge my S85 to 90% and don't worry about it. I used to charge to 100% for trips, but now with superchargers so common throughout the portion of California I visit I just don't bother anymore. It has become 90% every night. Sh-h-h; don't tell anyone, but sometimes I forget to plug in on weekends. Whatever, it's not a big deal. Do 90% and forget it.

gordo | 11 août 2015

I have a script that sets my charge every night. 70% for weekdays (~45 mile round trip commute) and 85% for weekends. I manually set it to 100 for any trips.

vlad22 | 11 août 2015

I always charge mine to 90% even though I only usually drive about 70 miles a day. That worked out well for me today. Last minute tee time with a client 85 miles from work. Managed to get there, back, head to a dinner meeting and made it home with 21 miles left. Not cutting it close but when I see the yellow line appear and the battery colour turning orange it becomes a little iffy... I used to see 418-421 on a full charge, now down to 408 at 15500 kms. Ps. All numbers are km. for you Yankees divide by 1.6

Blu Zap | 11 août 2015

70% daily driving. 90% if I am driving to a destination over 65 miles and back. 100% only when I take a long trip.

Roamer@AZ USA | 11 août 2015

I charge to 80% for local driving and charge to 100% for road trips. I leave it set at 100% whenever I am distance driving then set it back to 80 when I reach my destination. Sometimes lunch on the road takes longer so it just as well keep charging up to 100%. Then less time at the next stop.

My rule is, if the wheels are not turning then it is plugged in and charging. I never think about it I just always plug in whenever I can.

My car lives its life going from 100 to 5 over and over. My wife's car lives its life going from 80 to 50 and back to 80. Every few months I charge my wife's car to 100% then don't plug it in until it gets to 10%. That seems to keep the computer range calculator happy.

I plan all charges to never leave the car sitting at 100% or less than 10% for any extended period of time.

Roamer@AZ USA | 11 août 2015

@Duma, I vote with JT. The guidance is to leave it plugged in, especially if you are not driving it for long periods. So just keep it plugged in and let the computers do the work. So when you are at home just leave it plugged in.

prp | 12 août 2015

@duma, if you are going to quote from the manual, you can't be selective. As written by you but not highlighted in itallic "the most important way to preserve your battery is to leave your model s plugged in when you are not using it."(noting this is one complete sentence)
Thats not a difficult sentence to understand. It's also repeated several times in the manual......and I'm siding with the engineers that created this masterpiece.
Now the question of how much charge, the answer is on your charge screen or app, daily use anything from 50-90%. I use 90% because thats what my national tesla battery specialist recommended. If you're going on a trip, the same screen recommends 90-100%.
In my opinion, anyone using parameters outside those recommended in writing by tesla is dicing with extra degredation.

Red Sage ca us | 12 août 2015

Bump to find out!

Rocky_H | 12 août 2015

@prp, Quote: "I use 90% because thats what my national tesla battery specialist recommended."

OK, but that is because they want to have one-size-fits-all advice that they can give to everyone that may not be ideal, but always works. 90% is a good balance of not being right up at the top to stay away from the really bad degradation, but it gives people confidence at having plenty of range if they do a lot of driving.

Having additional information, though, never hurts. Knowing that Li-ion batteries just generally are healthier staying away from the extreme ends of the charge level, gives some additional guidance if you want to use it. Since we never come close to using 90% of a charge in even a couple of days, I have it turned down a little bit to where it's right around 200 miles (75% or so). Probably not much of a difference, but maybe slightly better.

markvallaster | 12 août 2015

I've seen lots of recommendations like this but have wondered if tesla has any data about actual charging patterns and performance. With the roadster and the model S, there's certainly a good sample size out there to draw from.

s1 | 12 août 2015

I found this to be useful. I take it to suggest that you should keep your average charge as close to 50% as possible. Thus, if you have a 250 mile range and a 50 mile daily commute, you'd want to charge it to 50% + (50/2)/250 = 60%.

J.T. | 12 août 2015

From the FAQ:

Charging and Range

Recommended level of charge is between 50%-62%. Only max charge when absolutely necessary. Do not go below 10 Miles To Go unless necessary. Always keep car plugged in when not in use when possible. Many discussion threads on this topic.

And more being started every day.

jordanrichard | 12 août 2015

Looks everyone scared off the OP.

OP, it is up to you whether to charge to 50 or 90 %. Anything higher is only recommended if needed for a trip.

There are those that only charge to what they expect their needs to be. I charge to 90% regardless because I like having the flexibility to drive much further if I needed to.

lecompte | 12 août 2015

This is fantastic information... thanks guys!

QWilson | 20 novembre 2019

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