Charge Daily or Charge as needed?

Charge Daily or Charge as needed?

I'm a happy MS owner that wants to get your input.

The Tesla Model S owners manual says keep your Tesla plugged in whenever you can. My service advisor said charge at different milage intervals and if you only need to charge once a week that is OK...

Charge Daily or Charge as needed?
What are your best practices?

2kids10horses | August 3, 2014

I charge when I get home. I have a HPWC, the business end is right at the drivers door. I get out, grab the handle, push the little button, plug in and go.

I always have a "full charge". One more thing I don't have to worry about.

jai9001 | August 3, 2014

From the owners manual:

"There is no advantage to waiting until the

Battery’s level is low before charging. In fact,

the Battery performs best when charged


Chunky Jr. | August 3, 2014

I have had my car over a year and tend to charge every night, but sometimes I get lazy and go a few nights without doing it. To me, it is mostly a habit to plug in at night. I don't really think about whether it is optimal or not and figure the software will determine the best thing to do.

carlk | August 3, 2014

You can plug it in whenever you can but set the charge limit to 80% or 70% other than when a long trip is planned. From everything we've heard from Tesla the charged state at around 50% is the best. A long periond of time at near full charge or empty is bad for battert life. How much difference that makes is anybody's guess.

hcwhy | August 3, 2014

I plug mine in whenever it's in the garage (unless I forget, which happens occasionally). My delivery specialist told me that a plugged in car was a happy car, and that, unlike the cell phone, a short charging time isn't harmful. Anything to keep the car and the dog happy.

johncrab | August 3, 2014

Unlike the Leaf which has to be plugged in after a run to the Safeway, a MS doesn't need to be plugged in every time it is stopped. If you are in and out all day, don't drive yourself crazy by plugging and unplugging but plug in when you are in for the day and let it manage the battery by itself.

mgboyes | August 3, 2014

The simple answer is that as long as you don't go below 10% or above 95% state of charge every day it really won't make the slightest bit of difference. All other debates are arguing about perhaps a 1% difference in capacity a few years down the line.

Just do whatever works for you.

I plug in every day and the car charges overnight on an offpeak tariff.

Fins | August 3, 2014

Thanks I will now plug it in every night instead of every few days...

Pilot_51 @US-MI | August 3, 2014

I usually plug in when I get home out of habit (a habit which took me no time to get into, perhaps thanks to cell phones). I have to think about it if I decide not to plug in, like today when I'm going out again before the scheduled charging starts at midnight.

For charging limit, my general rule of thumb is to set it so that your daily commute ends around 50% capacity, as long as it doesn't mean going above 90% (trip range).

Anthony J. Parisio | August 3, 2014

This is what I understand. Keeping it plugged in is also about keeping the batteries cool or warm depending on the environment. It is not just about how much charge you have. Everything that people said so far about charge, in response to your question, seems to be true. However, they did not mention about keeping the battery cool or warm. This might be why Tesla suggest keeping it plugged in all the time. If it is not plugged in then The car will use battery power to keep the pack at the right temperature. This is probably not even that critical unless the temperatures is extremely hot or extremely cold. I hope this helps.

Jewsh | August 3, 2014

Parasitic reactions (consumption of the electrolyte) are more pronounced on most lithium ion batteries as the voltage contained in the cell goes higher. On NCA cells a voltage of 4.2v is already high with (my understanding) 3.7v being the low side of things.

In theory keeping the batteries at the usual 90% SoC after a normal charge should be more abusive to the cells but in practice Tesla has seemingly come up with a fairly good chemistry... I have 53,000km on our car and we do not note more than what others have noted in terms of degradation and we charge to 90% every night and let it sit from ~10pm until 8am. (We lost about 0.5% capacity - 2-3km of range. Even that's debatable since the firmware has been more or less optimistic based on the release.)

I say plug the car in each night!

Anthony J. Parisio | August 3, 2014

I just saw a video about a car that was left for 27 days on plugged. Because the battery was not being warm or cooled there was no regenerative braking when the car was first start. A warning came up that the battery was being warm. This warning also said the power would increase as battery warms. This supports what ice said in my earlier post. Keeping the Car plugged in is also about keeping the batteries at the right temperature. It is not just about keeping them charged.

J.T. | August 3, 2014

@Anthony You would get that warning regardless if ambient temperatures are near freezing.

Bighorn | August 3, 2014


It's been so long since winter, but I seem to recall limited regen any time the temp was below 50F. Was that Bjorn's video, because it would have been cold there.

avanti5010 | August 3, 2014

@johncrab: How far is your Safeway from home? 35 miles?

DonS | August 4, 2014

Normal for me is charge to 80% (i.e. ~200 mile range) and plug in any evening it gets down to 110 miles (which is about 40% capacity). Sometimes that means daily charging and sometimes it is several days. 90% and above is only used occasionally.

Brian H | August 4, 2014

I assume TM is getting petabytes of data and learning about how their packs perform under many conditions. They may be eventually able to fully answer the French Scientist's Question: "That may be fine in practice. But how does it work in theory?"

Pungoteague_Dave | August 4, 2014

@Anthony - "Keeping it plugged in is also about keeping the batteries cool or warm depending on the environment." - that statement is incorrect. The car will maintain the battery temperature within specs no matter what the ambient exterior temperature and whether or not plugged in. If the battery is in danger of freezing at any time, the car will heat it, using the battery itself, or the wall power if it is plugged in. The added heating and limitation on regen that you reference occurs when it is cold and the car needs to get the battery up to OPERATING temperature, which is different than what happens while parked/in storage.

hamer | August 4, 2014

@Brian H: Je suis insulte'

Dnbigd | August 4, 2014

Agree fully with P_Dave. And me thinks we belabor this issue too much. As long as the battery is not approaching a low SOC it will have plenty of capacity to warm or cool itself overnight without being plugged in. Tesla's advice to keep car plugged in must be their way of making sure we don't forget to charge and run it down too low. The power to warm/cool the battery comes form the battery anyway and keeping it plugged in then just replaces what was used.

Rocky_H | August 4, 2014

@P_Dave, I would say it doesn't seem totally incorrect. I'm sure it will use its own battery power to heat or cool to keep it within its outside specs to not damage the battery, but it does seem to use wall power if available to move it even farther to an ideal temperature point. Here is what mine did recently:

We've been having days with the temperature in the high 90's or a little over 100 degrees. Our drive home is about 2 miles, so we drove home one day, and pulled in the garage, parked and got out (so car was still pretty hot). I wasn't planning to plug it in at the time, so I was starting to head into the house. Then, I did remember this and that it had been sitting at 100 degrees throughout the day, so I was wondering a bit why it wasn't running the cooling fans. I went back and plugged it in, and as soon as I did, the cooling fan blowers started up.

It seems that there is a balance of making sure the temp stays safe enough, but not wanting to run down the battery unnecessarily. But if wall power is available, then it will heat or cool it a bit more. So during the intense parts of summer and winter, I am going to make sure to plug it in as much as possible in case it does want to manage the temp more.

Anthony J. Parisio | August 4, 2014

Rocky_H experienced what I was talking about. The car will heat and cool it's batteries to optimum performance temperature if it is plugged in to wall power. If it is only on battery it will keep batteries from temperature extremes. I forget where I read this but after charging dose not the car continue to pull power as it needs to do other things like battery conditioning?

ir | August 4, 2014

When not charging, the car can use "shore power" to run the AC / Heater. For example, if you enable climate control remotely.

When parked and not charging, the car will use the AC / Heater to keep the car from extreme temperatures. BUT it will NOT keep the battery at "optimal" temperature. On a cold day, you can still get the battery warming message even if it was plugged in overnight!

As a workaround, some folks remote enable the AC / Heater before the leave home to trick the car into pre-warming the battery. Since the battery heating / cooling loop is tied to the cabin heater / cooler, they will both warm / cool at the same time.

Another trick is to reduce charging power so that the battery finishes charging just before you leave.

In short, there are 3 temperature "bands":
"extreme" hot / cold: Car will use any means available to stay out of this range.
"charging" temperature: Narrower range that the car will warm / cool to in order to safely charge the battery.
"operating" temperature: Most narrow range, to provide optimal regeneration and acceleration.

Tâm | August 5, 2014

I think what the rep means is: If this is what keeps you from buying then don't sweat over it:

It's best to plug in whenever there's a charger or outlet available.

However, if you live in an apartment and can't access a charger or outlet for a whole week, then that is not best but it's perfectly ok.

Either way, you are covered for the next 8 year, unlimited mile for your 85 kWh pack.

Anthony J. Parisio | August 5, 2014

Thank you. Tam you are right.

J.T. | August 5, 2014

@ir I have yet to find the "secret sauce" that allows me to drive off without orange dotted lines in cold weather. I have tried preheating the car for 30 minutes while charging at 40 amps for 30 minutes. I've also tried charging at 40 amps for 30 minutes, unplugging, then preheating the car for 30 minutes, using the battery to heat the car rather than shore power, and they are still there. Also tried setting charging at 20 amps for 4 hours before departure, still no joy.

The only thing that might work is asking my wife to drive the car until the lines are gone. But then she won't come back and I'll be driving the A6. I'll take the orange lines.

john.morello | August 5, 2014

Thank you for all the great contributions in this thread, they are super informative and my wire and I are looking forward to putting the thoughts on charging into practice, hopefully less than a month to go until the model S arrives.

@ir the penny dropped for me when you explained the three operating temperature bands of the battery pack.thx and impressive engineering by Tesla.

AndyO | August 5, 2014

Side question: Does anyone know the actual temps for ranges? I understand we don't really need to know but the engineer in me wants to know.

Brian H | August 5, 2014

Another item I believe 6.0 is supposed to fix (warm at scheduled time for departure). IIRC. Or SLT. Maybe even learn such routines by geo-fencing?

jordanrichard | August 5, 2014

Tesla considers 90% as the "standard charge". When using the app and setting the charging limit, if you select Standard, it will stop at 90% charge.

This is what I use every night. Granted there are nights when I don't bother plugging it in if I only drove 20 miles during the day, but generally it gets plugged in everynight.

There are those who believe you should only charge to what your daily needs are. That is all well and good if nothing comes up that requires you to drive further. Today was a perfect example of this. I charged to 90% last night and that got me 236 rated miles. Went to the office this morning, and got a call from a friend who needed a last minute ride to the airport. Long story short, my daily drive of 15 miles turned into 120 miles. Had I charged to only 50%, this last minute need for range would not have been possible.

jbunn | August 5, 2014

I only have the chance to charge once a week for the last 15 months at my apartment. On the road I use superchargers, but for day to day, once a week, sometimes every other week is plenty.

Like one of the other folks said above, it's not a Leaf. You don't need to plug it in to go to safeway. I don't even plug it in when I'm running trips. Leave those chargers to the Leafs.

(In an incident of really poor behavior at Topanga Canyon mall this week, I took my nephew there to the Tesla paddock to see other colors and more cars lined up. Adjacent are two J1772 public chargers. One Leaf charging. One Volt taking up the other spot, not plugged in. So wrong on several levels. It's not EV paring, it's EV CHARGING. Secondly, a Volt is not even a real EV. If the Leaf does not have charging, he's hosed. If the Tesla does not have charging, he can get home. But the Volt? Feh. Drive on gas. But NEVER block a charging slots. Leaf and other short range BEVs need those.)

Brian H | August 6, 2014

'Best Practices' is a serpent with fangs. It must be made general enough not to cause problems in even corner cases. It sacrifices all relevant specifics in any individual case that might produce a better result in favor of not failing in the extremes. Same in medicine as in charging! In medicine, even if a doctor knows of a better alternative in a specific case, he may be unwilling and ill-advised to use it; if anything goes awry, and he gets sued, he will be condemned and culpable in any review or suit because he didn't follow 'best practices'. OTOH, if he does follow 'Best Practices' and things go south, his defense is solid.