akenham
M3 LR AWD+ 2020
Ah maybe that's the difference then - lowest has been about -3 degrees Celsius but typically from -1 to +5 degrees Celsius .
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Precondition car plugged in vs not plugged in
- Thread starter Darthbenji
- Start date
Ah maybe that's the difference then - lowest has been about -3 degrees Celsius but typically from -1 to +5 degrees Celsius .
This is my experience as well. If I didn’t leave myself enough time to sufficiently warm the car with your step 1, I have to use your step 2. Sometimes I’ll set the temp higher then I’ll need, but not “HI” to give it a little extra, but still have it cycle.
Short answer: kind of
Long answer:
What you observe (needing to charge to 92% if you want to leave with 90%) is often true whether or not you precondition the cabin, but especially in winter. After finishing a charge, your battery will cool back down. When colder, the car will report less percentage - if your battery was magically warmed without using energy, it would actually "gain" percentage. Even at just 10C/50F (so, not that cold) you can read as much as 2% lower (due to rounding especially), and the snowflake icon comes on at 2%.
This next statement of yours is technically true, but I think you may be looking too far into it: "The battery doesn’t charge while heat is on". That's true, but not the same thing as the car not pulling power from the wall. For larger loads (e.g. heating the cabin), it will activate "charging", but just to loosely equal the power needed by the car at that times. Basically, it floats around net zero. However, light loads (e.g. Sentry Mode) tend not to activate the charger. Instead, it will wait until the battery has dropped a few percent, then charge back up to the charge target that you've set in the car/app.
But, you say your car isn't doing this. There might be a couple reasons for that. Your climate control load may be too small to trigger it to pull power from the wall - this could happen if the target temperature is very close to the cabin temperature already. Or perhaps there's some combination of settings (e.g. when using Scheduled Departure - I haven't tested with that) which alters the behaviour. In fact, I recall folks on here when that feature was first released saying the car would noticeably discharge if they were an hour late getting into their car, implying it wasn't pulling wall power at all. In my case, the notes above applied to both Scheduled Charging (not Departure) and on-demand charging (e.g. at a hotel or something). So yeah, Scheduled Departure is my blind spot, if you're using that.
Tag worked, wouldn't have seen otherwise. Hopefully I didn't repeat anything, I didn't read the rest of the thread
JCtx
Member
New 2021 owner here. My wife likes preheating the cabin for about 3 minutes before leaving. Today I heard a loud noise, and figure it was odd, until reading this thread. Apparently the car is preheating the battery pack as well. My question is if it's worth draining the battery to preheat it? And if no, is there a way to turn off battery heating when preheating the cabin from the app?
Finally, I'm following the advice of some folks on this forum (and a Tesla manager) to maximize battery life by not leaving car connected to the wall every day. Waiting until it gets to around 20% before recharging back to 90%. It's at 31% now (110 miles), but it's losing juice every day, due to garage being like 50F.
Finally, I'm following the advice of some folks on this forum (and a Tesla manager) to maximize battery life by not leaving car connected to the wall every day. Waiting until it gets to around 20% before recharging back to 90%. It's at 31% now (110 miles), but it's losing juice every day, due to garage being like 50F.
Yes, it is worth preheating. Tesla have done the math here, they know the battery chemistry, the cost of preheating, and the benefit.
as for charging, there is a lot of voodoo here, but as Tesla officially say, charge it to 80% or less for normal use, and otherwise forget it. There is no reason to run the battery to a low SoC, except to trigger the BMS, and even that doesnt alter battery health, it just makes the range display slightly more accurate. Just plug it in when you get home and relax
About not leaving the car connected all the time, check out the manual. It mentions in at least 2 sections to plug it in whenever you can. Not sure why the opposite has taken hold.
Same for me with an SR+ and just 3 kW charging power, except I have only 60% and charging rate is usually zero. It uses the charging current to heat up the battery and the interior and takes some from the battery as well, because 3 kW don't cut it initially.
If I wait until everything is warmed up, it seems to need a bit less than 3 kW for keeping warm, and so I get some charging.
My impression was that only the newer software versions provide battery pre-warming when the car is not connected to a charger. I can confirm that behavior.
I think you've been given bad advice. The only grain of truth in it is that it isn't very good for the battery to be kept at 90% continuously.
A better strategy is to connect whenever possible and set the charge limit to a sensible value, which depends on how much you need. The lower you go (down to 60%), the longer your battery will live.
Since I don't drive long-distance often, I charge only to 60%, but up to 80% will not make much of a difference. I do charge up to 90% and even 100% when I need it.
Brock-WI
Member
For reference we have a gen 3 wall connector that is capable of 48 amps, however we currently only have a SR rear motor only which can only charge at 32 amps. I also have "scan my Tesla" app which lets you see in detail what the car is really doing. Right now I went in the app and turned on the climate, right away it turned on the wall charger and started pulling about 3kw additional from the battery pack. So I believe what I am seeing is the rear stator/motor heating at 3.5kw and the resistance heater pulling 6kw to heat the cabin. After 5 minutes or so it drops to about 0kw from the battery, but still pulling power from the wall and I can still see the 3.5kw ish to the rear stator heating the battery and the cabin heater stabilizing and varying what it pulling, but usually less that 3.5kw so the traction battery charge remains about the same. After 15 minutes the cabin heater uses even less power and it starts to add that power to the traction battery and it starts to gain in %.
Interestingly I have never see the motor heating stop, after an hour getting the pack to 85F (garage at 35F) but I have never ran it for more than an hour to see at what temp it stops trying to heat the battery up.
I would imagine a dual motor runs both motors pulling 7kw to heat up the battery in addition to the cabin heat but can't verify that?
I also am not sure how the heat pump models play in to this other than swapping the 6kw resistance heat for the heat pump. Although I thought Bjorn said it can use the same battery/motor heat to heat the cabin as well,
Interestingly I have never see the motor heating stop, after an hour getting the pack to 85F (garage at 35F) but I have never ran it for more than an hour to see at what temp it stops trying to heat the battery up.
I would imagine a dual motor runs both motors pulling 7kw to heat up the battery in addition to the cabin heat but can't verify that?
I also am not sure how the heat pump models play in to this other than swapping the 6kw resistance heat for the heat pump. Although I thought Bjorn said it can use the same battery/motor heat to heat the cabin as well,
I just realised a big detail I left out in my last post, which was more important than I thought now that I've done the math!
The car can draw more power than is available from the wall even when connected/"charging" for preconditioning. It's a common myth that the car will limit its power draw when preconditioning to the power available from the wall - this is not true. So for lower power charging setups, you can very easily have a net power draw on the battery, and indeed end up losing a bit of charge for preconditioning even though it's using wall power. However, due to the battery heating behaviour now, the car can result in a net discharge even on high power setups!
For those on 240V/32A setups, you wouldn't really notice any drop unless you have an AWD and it's a short preconditioning. The 7-8kW for battery heating, plus whatever heat load for the cabin (up to 7kW to start, which calms down to 2-3kW pretty quickly) will slightly exceed the ~6900W you have available from that setup (after accounting for losses). In fact, even on this setup, preconditioning for 15 minutes is enough to drop it about 1.5% in many setups if both cabin and battery heat are going (for AWD). And 1.5% could sort of show up as 2% to the user, because of rounding. But 2% would be about the most you'd see in this case, as the heating needs would drop, allowing the available wall power to fully subsidize what the car is using.
So that might explain why OP is seeing the capacity drop even when plugged in!
For an SR+ or RWD model on a 240V setup, it'd be hard to greatly exceed the available wall power, so these should see less drops I'd expect.
"Worth it" depends on what you value.
I still preheat the car sometimes of course because of the last point, I just don't like that it wastes so much on heating the battery as well. Thankfully, if preheating for only 3 minutes, it's not too bad.
Btw, anecdotally and with no further references, storing a cold battery has been described to be healthier at higher percentages than low ones. You can really overthink this though and you'll get hundreds of conflicting advice points, mine probably included.
The car can draw more power than is available from the wall even when connected/"charging" for preconditioning. It's a common myth that the car will limit its power draw when preconditioning to the power available from the wall - this is not true. So for lower power charging setups, you can very easily have a net power draw on the battery, and indeed end up losing a bit of charge for preconditioning even though it's using wall power. However, due to the battery heating behaviour now, the car can result in a net discharge even on high power setups!
For those on 240V/32A setups, you wouldn't really notice any drop unless you have an AWD and it's a short preconditioning. The 7-8kW for battery heating, plus whatever heat load for the cabin (up to 7kW to start, which calms down to 2-3kW pretty quickly) will slightly exceed the ~6900W you have available from that setup (after accounting for losses). In fact, even on this setup, preconditioning for 15 minutes is enough to drop it about 1.5% in many setups if both cabin and battery heat are going (for AWD). And 1.5% could sort of show up as 2% to the user, because of rounding. But 2% would be about the most you'd see in this case, as the heating needs would drop, allowing the available wall power to fully subsidize what the car is using.
So that might explain why OP is seeing the capacity drop even when plugged in!
For an SR+ or RWD model on a 240V setup, it'd be hard to greatly exceed the available wall power, so these should see less drops I'd expect.
"Worth it" depends on what you value.
- "Green" reasons: No, it's a net waste of energy for 99.9% of applications, probably 100%.
- Financial reasons: No, for the same reason it isn't "green". It consumes a lot more energy you'll not gain back by the increased regen.
- Driving experience reasons: Maybe, if preserving the feel of high regen braking force is of high importance to you.
- Reliability reasons: No. The car already sufficiently protects itself (this is why regen is limited in the first place). Wasting all this energy to heat it isn't doing a net good, and for some people (frequent low distance trips) could actually contribute to faster battery wear. It's a lot of energy compared to locomotive energy for those that don't drive far, and both contribute to the ultimate cycle count on your battery pack.
- Comfort reasons: Maybe. Unfortunately, to heat the cabin you must now heat the battery as well. But a warm cabin has many benefits: not being cold (better driver, less distracted, less miserable), clearer windshield (better driver), and potentially not-frozen hands (turns out you need those to steer the car).
I still preheat the car sometimes of course because of the last point, I just don't like that it wastes so much on heating the battery as well. Thankfully, if preheating for only 3 minutes, it's not too bad.
Btw, anecdotally and with no further references, storing a cold battery has been described to be healthier at higher percentages than low ones. You can really overthink this though and you'll get hundreds of conflicting advice points, mine probably included.
That advice (not to leave it connected to a wall connector every day, and to drain it down before filling it back up) SPECIFICALLY Contradicts the information that is printed in the manual for the car. Tesla has a LONG history of "people in service centers" saying specifically stuff that is wrong. What you choose to do is up to you (and who you choose to believe), but there is no advice anywhere that says its best to run the car down before filling it back up like its a phone.
The car manual specifically says (currently on page 179)
======================================
About the Battery
Model 3 has one of the most sophisticated battery systems in the world. The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model 3 for several weeks. When plugged in, Model 3 wakes up when needed to automatically maintain a charge level that maximizes the lifetime of the Battery.
NOTE: When left idle and unplugged, your vehicle periodically uses energy from the Battery for system tests and recharging the 12V battery when necessary.
There is no advantage to waiting until the Battery’s level is low before charging. In fact, the Battery performs best when charged regularly.
=======================================
Now, if you choose to believe some guy in a service center over the printed manual of the car regarding "running it down to fill it back up" being somehow BETTER, then thats up to you. There are no posts here that recommend that. There ARE posts here that say that you should have the car at various states of charge to help the "little number on the screen" otherwise known as the range number display a higher number.
There is no "mandate" that the car "has" to be plugged in every day, and there are plenty of people who dont for some reason or another, but there is no one here at all that has ever said that it is BETTER to run the car down before charging it than it is to simply plug it in. You mentioned this before, and we told you that whatever that "tesla manager" was saying obviously contradicted everything we know... including the information coming directly from tesla.
I have to think that there is some "telephone game" going on here where what the manager actually said is something slightly different than what you report, because even though tesla has a history of their people saying stuff that isnt true, no tesla person I am aware of has ever said "its better to run the car down before charging it up". Yours is the first I have heard of.
JCtx
Member
Yeah, you don't know what to believe anymore. Ha ha. Supposedly, Tesla recommends that so people don't forget to plug the car, but that it's not the best approach for longest battery life.
The first time I heard about not keeping car connected all the time was the Tesla store manager that sold me the car, who seems very knowledgeable. And then from many forum members here who reported excessive degradation by doing just that. And that it started to get reversed when discharging battery to 20 to 30%, then back to 90. And that was a fully stock car, with no other apps or software. So who knows. Will keep reading, and for now, use that strategy, which is up to 90 in winter, and 80% when hot (summer). Will try a supercharger today, just to make sure all goes well, since we're going on a long trip on the 14th.
Not very good for phone batteries either. They are only run down during the day ouf of necessity, not out of battery care. Phone Li-ion batteries are very similar to car Li-ion batteries and have similar ways to degrade.
The new LFP batteries in the SR+ Made in China are somewhat different in this respect, but not fundamentally different.
JCtx
Member
So how can you guys explain a forum member reversing his excessive battery degradation due to leaving car always hooked by letting battery drain before recharging? There's a long thread on this same forum. Look for it, and then come back and see if it made sense to you. It gets very technical, including the why that happened, which has to do with how the car reads battery charge, and how it needs to be changing, for best battery 'balancing'.
I just bought the car, and it's our first every anything electric (hybrid, EV, etc), so just getting acquainted with it. In the mean time, I'll go to the 'middle' of both approaches, so charging to 90% (80% in summer), and letting it discharge only to 50%, then recharge again. And will keep reading the forum, to learn more, and change the way I do that if needed. By the way, the OP of that degradation thread I mentioned above, said he talked to the actual head of battery tech at Tesla, if I remember correctly, and he recommended doing that to reverse excessive battery degradation, and it's been working, and the guy is a long time Tesla owner, and got very technical, so not your average owner's manual-reading owner. But curious what other owners like you guys think, after reading that thread. Thx.
I just bought the car, and it's our first every anything electric (hybrid, EV, etc), so just getting acquainted with it. In the mean time, I'll go to the 'middle' of both approaches, so charging to 90% (80% in summer), and letting it discharge only to 50%, then recharge again. And will keep reading the forum, to learn more, and change the way I do that if needed. By the way, the OP of that degradation thread I mentioned above, said he talked to the actual head of battery tech at Tesla, if I remember correctly, and he recommended doing that to reverse excessive battery degradation, and it's been working, and the guy is a long time Tesla owner, and got very technical, so not your average owner's manual-reading owner. But curious what other owners like you guys think, after reading that thread. Thx.
One thing people get confused about here is the actual charge level of the battery, the actual range of the car, and the reported charge and range. Many of the so-called fixes for "battery degradation" are just recalibration of the BMS itself. There is no direct way to measure the total quantity of charge stored in a Lithium battery. Instead it's approximated by measuring various indirect values of the battery pack, including voltage at a given temperature, the age of the battery etc. This approximation is good, but not perfect, and one way to improve the approximation is to give the BMS more data to work with .. and that includes letting it see battery voltage with the battery at different SoC levels. Once the BMS has this data, it can more accurately determine the charge. In the meantime, when it doesnt have enough data, what does it do? It errs on the safe side, and underreports the charge level slightly. Why? Because its better to have you go to a charger a little bit sooner than you needed to than it is to run out of battery power in the middle of nowhere. That's why, when you do recalibrate, the range of the car appears to increase.
So, what is mostly happening, is people are recalibrating the BMS to more accurately measure the battery, they are not "healing" the battery at all .. it stays with the capacity its had all along .. its just that the car is more accurately reporting it. There is a slight overall health benefit in the form of cell balancing (making sure all the cells have the same approx charge level), which probably has a small beneficial effect on long-term health since it makes wear slightly more even across cells, but I've never seen any clear data about such an effect.
Of course, the battery does indeed degrade over time. But most of the things that cause actual battery degradation are irreversible and to do with the basic chemistry of the battery, though they can be minimized by certain battery usage disciplines. This includes not charging to 100% too often, not fully discharging (ever), and charging/discharging moderately (most of the time).
Yes, it is worth preheating. Tesla have done the math here, they know the battery chemistry, the cost of preheating, and the benefit.
as for charging, there is a lot of voodoo here, but as Tesla officially say, charge it to 80% or less for normal use, and otherwise forget it. There is no reason to run the battery to a low SoC, except to trigger the BMS, and even that doesnt alter battery health, it just makes the range display slightly more accurate. Just plug it in when you get home and relax
No, Tesla knows how whiny customers are and that's the math they use.
In my experience it never "pays" to Preheat cabin or battery. Especially on a very short commute. But even on long ones it doesn't "pay" (it's a net loss on energy for more comfort).
I know the thread you are talking about, and the very high level version (TL ; DR version) is to do that "occasionally" to allow the battery maintenance system (BMS) to calibrate properly. There was never any advice to do that as a general charging practice.
That was also advice given to make the range number on the screen read higher (because you cant actually reverse REAL "degradation"), and to address something you have not had a chance to experience yet, because your car is new. TL ; DR is it doesnt apply to your situation yet because you havent experienced the range number reading lower due to the BMS getting out of whack.
But again, its your car, you do what you find appropriate. I have had my car plugged in and charge to 90% and I plug it in every time it hits my garage. I have 25k miles on my model 3, and my 100% charge is 299, which is what tesla rated my car for new with 20 inch wheels.
If it's the thread I think you're talking about, here's the explanation: confounding factors.
Most of us aren't running good science here, myself included. In that thread specifically, OP did two huge things along with changing the discharge behaviour:
- Stopped using Sentry mode all the time, to allow it to sleep.
- Let the car rest more often at higher SoC.
It's also worth noting some of these established Tesla employees may have a better understanding of the behaviour of Model S/X packs instead of 3/Y, and they behave very different.
I’ve been told the same by my service center. Run down to below 20%. Let it sit for 3 hours at least. Charge up to 80 or 90% then unplug and let it sit for at least three hours. Don’t wake it or have sentry running. Do this 4-5 times over a month or so. Supposed to help with displayed range.
So they aren’t really going off manual. They don’t ask you to do it constantly. Once a week or so.
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