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Charging Question

asolof

Member
Sep 26, 2020
38
6
New Jersey
The Model Y manual says "To prevent an excessive amount of energy consumption while the vehicle is idle, keep the vehicle plugged in when not in use."

So, let's say the vehicle's current charge is 70% and I don't want to charge it yet. If I have it plugged into the charger, but not charging it, will it prevent "vampire drain" and also use energy from the wall charger to preheat the car in cold weather?
 

animorph

Active Member
Apr 1, 2016
2,152
1,580
Scottsdale, AZ
What is your charge limit setting? Is it a scheduled charge or charge any time?

Normally the car will charge when it is about 3% below the charge limit. It will wait until the scheduled time if you have that set, unless it is only a few hours after that time when it falls enough to charge. It will draw from the charger for preconditioning or if you have opened the door and climate is on. But normal vampire drain will slowly reduce the battery charge, even when plugged in. So eventually you will see the car actually charging.

Plugging in simply ensures the battery is topped up and ready to go. And it avoids those occasional threads about leaving the car unplugged and being unavoidably delayed while you watch the charge level drop to 0% in the Tesla app.
 

asolof

Member
Sep 26, 2020
38
6
New Jersey
animorph

"What is your charge limit setting? Is it a scheduled charge or charge any time?" I should be getting my car delivered sometime this week. I was reading the manual and wanted clarification on that statement. I drive 15 to 30 miles per day on average during weekdays and was thinking about using a charging strategy of charge to 90% and recharge if the charge drops to less than 30% upon arriving home on a given day. This comes to about once per week. I'm used to caring for lithium batteries because I'm into the RC aircraft hobby. The batteries last longest when stored at around 50% charge; especially avoiding prolonged periods at the extreme ends of high/low charge. Therefore, knowing what happens when the care is plugged into the Tesla wall charger, but not charging is useful.

So the wall charger will preheat/adjust the car's cabin and car battery temperatures (sparing the car's battery charge), but do nothing else; that is, will not maintain the current battery charge so not preventing vampire drain.
 

SSonnentag

Let’s go Brandon!
Apr 11, 2017
1,748
2,352
Arizona
Normally the car will charge when it is about 3% below the charge limit.

This used to be the case, but for the past several updates our cars have been "topping up" much more frequently. Here's a TeslaFi snippet for example:

Charging.png
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,783
8,387
Boise, ID
I'm used to caring for lithium batteries because I'm into the RC aircraft hobby. The batteries last longest when stored at around 50% charge; especially avoiding prolonged periods at the extreme ends of high/low charge.
"Normally the car will charge when it is about 3% below the charge limit."

What charge limit are you referring to?
Yes, your experience is applicable to this as well, which is why the cars don't automatically fill to 100% all the time when they are plugged in; that would be unhealthy for them.

So what they have on the charging screen is that you can pick the limit of how full it will charge up. There is a picture of the battery there, with a little slider mark, and you can set that limit. The section from 50% to 90% is marked "DAILY", and the 90% to 100% area is marked "TRIPS". So a lot of people set that limit somewhere around 70 or 80%, to find a good balance of being near the middle for good battery longevity, but still having enough range to practically use the car.

There isn't really a benefit to intentionally running it down low, but it won't matter if you go at day or two in between charging. As long as you're mostly avoiding those really high and low ends for the constant daily use, that's good.

And if you have some cheaper electricity rates at night, you can also pick a charging start time, so it will only recharge once per day, during your cheaper overnight time window.
 
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asolof

Member
Sep 26, 2020
38
6
New Jersey
Rocky,

Thanks!

So, if I were to set it to charge to 70% daily and plugged it in every night it would charge to 70%, and then as vampire drain dropped the battery's voltage it would turn the charger on periodically to maintain it at the 70% charge (in addition to "preconditioning from the wall charger" if I were to request that).
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,783
8,387
Boise, ID
So, if I were to set it to charge to 70% daily and plugged it in every night it would charge to 70%, and then as vampire drain dropped the battery's voltage it would turn the charger on periodically to maintain it at the 70% charge (in addition to "preconditioning from the wall charger" if I were to request that).
Heh, well, that is how it is supposed to work, and did for several years. It doesn't keep kicking in every minute as soon as it drops, so it allows about 3% below before it will kick in to refill.

But in the past year, there have been some threads on this forum about people seeing it kicking in and doing these really tiny recharges way too often, and I'm not sure if that software gremlin has been fixed or not. So that's why I did mention setting a recharge time, so it doesn't keep trying to do that throughout the day.
 
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user212_nr

Active Member
Aug 26, 2019
1,407
874
US
Heh, well, that is how it is supposed to work, and did for several years. It doesn't keep kicking in every minute as soon as it drops, so it allows about 3% below before it will kick in to refill.

I've never seen my car not at the limit that it is set at, or more than one off, when plugged in and finished charging. Except charging to 100% sometimes stopped early. Personally, I'd be very unhappy, if I set the limit to 85, to see 82.

Maybe when it is cold out, it might determine it is not worth charging more. I'd be very skeptical that they use 3% and not 1%.
 

amnesty_that

Member
Sep 3, 2020
70
33
Bay Area
I charged my vehicle up to 90% on Sunday 10am and left sentry mode on. Monday as of 7:35p battery has drained to 79%

There is free charging around the corner & at work so I’m not really worried but seeing i don’t drive from Sunday morning at 12:30a till about 3:30p Wednesday would expect to lose ~ 10% a day while on sentry mode/ vampire drain?
 

LNL_HUTZ

Member
Aug 3, 2020
300
237
San Francisco
I charged my vehicle up to 90% on Sunday 10am and left sentry mode on. Monday as of 7:35p battery has drained to 79%

There is free charging around the corner & at work so I’m not really worried but seeing i don’t drive from Sunday morning at 12:30a till about 3:30p Wednesday would expect to lose ~ 10% a day while on sentry mode/ vampire drain?
That's a lot. Any chance the cabin overheat function was coming on during the heat wave? Or maybe the car was in a really busy area and Sentry mode kept getting triggered?
 

amnesty_that

Member
Sep 3, 2020
70
33
Bay Area
That's a lot. Any chance the cabin overheat function was coming on during the heat wave? Or maybe the car was in a really busy area and Sentry mode kept getting triggered?


Cabin overheat is off and the interior was getting up to 110 degrees plus as 100 degree day. Sentry mode on but when i got in only 2 events recorded. Which was annoying as a whole flyer was placed under every wiper on car on street and it didn’t catch it. First Tesla so i chalked it up as normal drain. If not that why here to find out. I do check the app regularly so that may contribute to drain but i would like to slow drain down.
 

LNL_HUTZ

Member
Aug 3, 2020
300
237
San Francisco
Sounds like you might want to replicate the conditions next time, but stay off the app and see if things change. I think there have been reports of insomniac Teslas.
 

Srad600Volt

Member
Sep 28, 2020
343
242
Southern California
So as a new owner, I'm curious if this is what most people actually do (plug the car in every night, even if the SOC is high)? I picked up the vehicle on Wednesday, charged it that night. Today (Saturday) the SOC is still at 50% and I haven't charged it since. I was thinking to let the SOC get down around 30% before charging back up again but this thread has me second guessing that thought.
 

jcanoe

Active Member
Oct 2, 2020
3,453
3,509
Maryland
Read the owner's manual, then follow your own path. Tesla recommends always plugging in the vehicle but if you don't drive many miles or every day is this really necessary or even beneficial? 50% is supposed to be the least stressful state of charge (SOC) for the battery pack but leaving the vehicle charged at 70%, 80% even up to 90% is fine too.

If you never charge the battery to above 90% the battery management system may not be able to accurately determine the top and bottom of the battery range; this could affect your ability to drive longer distances as the vehicle could shut down prematurely even when some battery charge remains.

I normally will charge my Tesla Model Y to 80% but I don't charge every day because I generally only drive less than 15 miles per day. I have been charging when the battery SOC reaches ~60%; it takes a little more than 2 hours charging at home (230V and 32 amps) to bring the battery back to 80%. If I charge to 80% and then decide to take a trip it only takes about an hour (at 230V and 32 amps) to add an additional 10% to the battery and charge to 90% SOC; a little over two hours if I ever decide to charge to 100% just prior to leaving on a long road trip.
 
Last edited:
Oct 3, 2020
205
239
Seattle
So as a new owner, I'm curious if this is what most people actually do (plug the car in every night, even if the SOC is high)? I picked up the vehicle on Wednesday, charged it that night. Today (Saturday) the SOC is still at 50% and I haven't charged it since. I was thinking to let the SOC get down around 30% before charging back up again but this thread has me second guessing that thought.

Lithium batteries do not like high or low states of charge, so it is recommended to cycle it so that it minimizes the amount of time it spends at either of these states. The battery can remain unplugged for days, if not weeks, without being plugged in (assuming sentry mode isn’t active), the ‘phantom drain’ is pretty slow.

I think waiting until it gets down below 30-40% before charging it back up to 70-80% is a good habit to practice in order to get the most life out of the pack. Unless you’re driving over 150 miles a day, or you’re going on a trip, you should not exceed this state of charge in order to extend the life of the pack.

Having said that, as long as your setting the charge limit to not exceed 70-80% for daily use, there’s nothing wrong with plugging it in everyday, but it isn’t necessary.
 

Srad600Volt

Member
Sep 28, 2020
343
242
Southern California
Read the owner's manual, then follow your own path. Tesla recommends always plugging in the vehicle but if you don't drive many miles or every day is this really necessary or even beneficial?

I have certainly spent some time with the manual, but I am unable to find this statement. In the section under charging instructions it goes over scheduled charging vs scheduled departure. It talks about how to physically plug in the vehicle and how not to. But I do not see where it states that the vehicle should be plugged in every day regardless of the SOC. If you could point me to that, that would be great. I do agree with everything else posted, and I also don't think it needs to be plugged in every day, because my current driving habits have me at about 5-10 miles a day (average).


Having said that, as long as your setting the charge limit to not exceed 70-80% for daily use, there’s nothing wrong with plugging it in everyday, but it isn’t necessary.

That is my thinking as well. I'm just curious what others are doing and what works well.
 

jcanoe

Active Member
Oct 2, 2020
3,453
3,509
Maryland
I realize we are in the Model Y forum; the following is from The Tesla Model S Owner's Manual, page 177.

Tesla strongly recommends leaving Model S plugged in when not in use. This maximizes the lifetime of the Battery Your Model S Battery is 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’re not using it. This is particularly important if you are not planning to drive your 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. This also protects the 12-volt battery. There is no advantage to waiting until the Battery’s level is low before charging. In fact, the Battery performs best when charged regularly.

https://www.tesla.com/sites/default/files/model_s_owners_manual_north_america_en_us.pdf
 
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