Sentry and cabin climate control battery drain

[mark chavez]

Everyone on this forum is obviously well aware of the battery drain that sentry mode and cabin overheat protection take on their respective vehicles. Just to add to the chorus of dismay, in barely 24 hours, my 2021 MYLR has been driven a total of 56 miles (almost all on the freeway averaging ~75mph). Although the average energy is 267Wh/mi with a total energy expenditure of 15 kWh, I managed to deplete my battery from 81% to 51%

As an interesting sidenote, I’ve been parked in my driveway for about 20 minutes to check out some things and noticed my initial battery % increased from 48% from when I first parked back up to 51% 20 minutes later…

Needless to say, the drain is real and unless you’re getting energy for free the long-term cost of such features is worth noting..

 

[jcanoe]

Set Sentry Mode to be off at your home location. Set Cabin Overheat Protection to Fan Only.

 

[rrolsbe]

Set Sentry Mode to be off at your home location. Set Cabin Overheat Protection to Fan Only.

If set to Fan only, will the car sleep when the cabin temp is below 105 degrees (like at night)?

 

[jcanoe]

If set to Fan only, will the car sleep when the cabin temp is below 105 degrees (like at night)?

Yes; I have Cabin Overheat Protection (COP) turned on (set to Fan Only mode) all year round. My 2020 LRMY is garaged at home and usually in sleep mode except when I wake up my Tesla Model Y using the Tesla app or when I enter the vehicle. (My garage will reach ~100F in summer, I have never observed COP when activated at home inside my garage but I may have missed it happening.) COP set to Fan Only mode won't hold the temperature of the passenger cabin to under 105F, probably 120F. Still, without COP the passenger cabin in daytime can reach 140F to 150F.

Cabin Overheat Protection only remains active for 12 hours after parking the Tesla Model Y.

 

[Joe2765]

Do Sentry Mode and Cabin Overheat protection draw from the battery all the time, even if the car is in motion?

I used a bit more than expected yesterday. I had parked with sentry mode but did not turn it off when I headed out for a long drive. While on the drive would sentry mode be still active and drawing from the battery? Same question for cabin overheat which was on and set to 90 degrees, but the AC was keeping it 70.

Thanks.

 

[jcanoe]

Do Sentry Mode and Cabin Overheat protection draw from the battery all the time, even if the car is in motion?

I used a bit more than expected yesterday. I had parked with sentry mode but did not turn it off when I headed out for a long drive. While on the drive would sentry mode be still active and drawing from the battery? Same question for cabin overheat which was on and set to 90 degrees, but the AC was keeping it 70.

Thanks.

Sentry mode and Cabin Overheat Protection are only active when the Tesla Model Y is parked. Sentry mode does not by itself cause additional drain of the battery. The Tesla Model Y remains in Standby mode whenever Sentry mode is active with the corresponding Standby mode power use of ~230 Wh. This is approximately 10X as much power as when the Tesla Model Y enters Sleep mode. In general use Sentry mode while out shopping, dining etc. but set Sentry mode to be off at the home location.

Cabin Overheat Protection is only active for 12 hours after the Model Y has been parked. Cabin Overheat Protection with AC can use ~750Wh/hr (3/4 of a kilowatt per hour) if the AC is allowed to run. In the No AC setting for Cabin Overheat Protection the power usage is less, i.e. ~250Wh/hr (about 1/3rd as much as when the AC runs.) Cabin Overheat with AC allows you to specify the cabin temperature limit (90/95/100F). Cabin Overheat with No AC does not have a cabin temperature limit but will keep the passenger cabin approximately 20 degrees cooler than without Cabin Overheat Protection set to run.

To minimize how hard the Climate Control system must work to keep the passenger cabin at the set temperature consider having the windshield, other windows tinted with a good ceramic tint film. Turn on Recirculate Cabin Air setting in the Climate Control settings during the warmest time of the day to reduce energy consumption. Depending on the temperature and humidity consider a cabin temperature of 70F and set the Climate Control to Auto. Be sure that the fan speed setting is set Med or Hi as in the Auto Climate Control mode this setting will limit the maximum fan speed to run too slowly if set to Lo.

 

[JpG1]

Last week, my Tesla Model Y purchased in February 2021 (mileage 19,121) parked in an Airport Parking garage for 10 days had no Power to open the car and my phone won't connect with the Car. When I left the car, there was 53% charge left on the Car. Tesla's customer service arranged for the Car to be towed to nearest Tesla repair center and I was told that the 12 Volt Battery which is needed for window lock operation died and disabled the lock system. When the car was opened and and began to charge, there was 42% charge left on the main battery. The Tesla repair center did not replace the 12V battery with the newer Lithium 12V battery which is 20 pound lighter and the answer given was they don't usually replace with "more expensive 12V lithium battery for these older Cars". I had no warning from the car that the 12v battery is going to die on me.

 

[jcanoe]

Last week, my Tesla Model Y purchased in February 2021 (mileage 19,121) parked in an Airport Parking garage for 10 days had no Power to open the car and my phone won't connect with the Car. When I left the car, there was 53% charge left on the Car. Tesla's customer service arranged for the Car to be towed to nearest Tesla repair center and I was told that the 12 Volt Battery which is needed for window lock operation died and disabled the lock system. When the car was opened and and began to charge, there was 42% charge left on the main battery. The Tesla repair center did not replace the 12V battery with the newer Lithium 12V battery which is 20 pound lighter and the answer given was they don't usually replace with "more expensive 12V lithium battery for these older Cars". I had no warning from the car that the 12v battery is going to die on me.

You were given incorrect information. Your early 2021 Tesla Model Y is not compatible with the newer Tesla 15.5V lithium starting battery module. You received the correct 12V lead-acid starting battery for your vehicle. Depending on the mileage on your 2021 Model Y the replacement 12V battery would have been covered under the Tesla new vehicle warranty.

 

[jjrandorin]

The Tesla repair center did not replace the 12V battery with the newer Lithium 12V battery which is 20 pound lighter and the answer given was they don't usually replace with "more expensive 12V lithium battery for these older Cars".

Its actually not "dont usually replace" its NOT POSSIBLE TO REPLACE with OEM lithium battery. Its not possible, full stop. The only way to get a lithium 12v battery in a tesla that didnt come with one from the factory is to use an aftermarket one (and some of those have had issues with battery management).

So, No, its not "usually dont replace" its "not possible with lithium OEM" so you didnt miss anything.

 

[lonertic]

Re Sentry mode draining battery - I've made a really interesting observation last night. I came home on the motorbike and walked past the parked Model Y (which had Sentry enabled even at home). As I walked past it, I can hear the AC running as you can hear the air getting sucked in the cabin air filter and a really quiet hum of the AC compressor (Credits to Tesla's latest build quality though, it's honestly really quiet, and I only managed to hear it because it was late at night and the garage was shut so the garage was dead silent with no other ambient noise)

I checked the app, the car is parked as expected (altho I think Walk away on lock exclude home is ticked, hence HAL didn't show up on screen when I walked past), the Climate page in app shows AC is *NOT* running, yet I can hear it from the outside. Turning climate on from the app makes no difference to the noise, turning it off actually stopped it. So that confirmed my hunch it was the AC... but then even with it showing as off on the app, a few minutes later the sound resumes and the AC comes back on.

This was around 10pm local time, the garage was a nice 21 degrees celsius, car wasn't plugged in, no planned trip or charging, not too cold/hot for cabin overheat or pre-conditioning of batteries/cabin that I can think of. Yet AC was just running when sentry was on! Maybe my proximity to the car had something to do with it but if we're at home, the phone would almost always be within bluetooth range anyway.

So that got me thinking, since a lot of people complain that Sentry drains batteries, and that just didn't register well with me, I'm used to multi-channel dashcams taking only a few watts of power, certainly not enough to make a noticable difference to a 70kWh+ battery pack. Even if you treat the dashcam as the entire MCU needing to stay on, so that's the equivalent of keeping a high-performance laptop on overnight - that would only max out at around 60-80W power consumption at full CPU usage. So why is sentry taking so much energy?

if AC is involved however, that suddenly makes sense! AC compressors are normally rated in the kW's... and with a cabin fan running when Sentry is on, we would be talking maybe 200-300 watts of compressor+fan energy consumption once it reaches whatever temp it thinks it needs to reach, but when the ambient is only 21c, why would it even need the AC for that? The MCU certainly doesnt get hot enough to need it.

Can anyone else confirm if their car is doing the same thing? that AC (or heater, or whatever was last left on "Auto" before you parked the car) just somehow comes on by itself minutes after you walk away from the car when Sentry is on?

 

[jcanoe]

Re Sentry mode draining battery - I've made a really interesting observation last night. I came home on the motorbike and walked past the parked Model Y (which had Sentry enabled even at home). As I walked past it, I can hear the AC running as you can hear the air getting sucked in the cabin air filter and a really quiet hum of the AC compressor (Credits to Tesla's latest build quality though, it's honestly really quiet, and I only managed to hear it because it was late at night and the garage was shut so the garage was dead silent with no other ambient noise)

I checked the app, the car is parked as expected (altho I think Walk away on lock exclude home is ticked, hence HAL didn't show up on screen when I walked past), the Climate page in app shows AC is *NOT* running, yet I can hear it from the outside. Turning climate on from the app makes no difference to the noise, turning it off actually stopped it. So that confirmed my hunch it was the AC... but then even with it showing as off on the app, a few minutes later the sound resumes and the AC comes back on.

This was around 10pm local time, the garage was a nice 21 degrees celsius, car wasn't plugged in, no planned trip or charging, not too cold/hot for cabin overheat or pre-conditioning of batteries/cabin that I can think of. Yet AC was just running when sentry was on! Maybe my proximity to the car had something to do with it but if we're at home, the phone would almost always be within bluetooth range anyway.

So that got me thinking, since a lot of people complain that Sentry drains batteries, and that just didn't register well with me, I'm used to multi-channel dashcams taking only a few watts of power, certainly not enough to make a noticable difference to a 70kWh+ battery pack. Even if you treat the dashcam as the entire MCU needing to stay on, so that's the equivalent of keeping a high-performance laptop on overnight - that would only max out at around 60-80W power consumption at full CPU usage. So why is sentry taking so much energy?

if AC is involved however, that suddenly makes sense! AC compressors are normally rated in the kW's... and with a cabin fan running when Sentry is on, we would be talking maybe 200-300 watts of compressor+fan energy consumption once it reaches whatever temp it thinks it needs to reach, but when the ambient is only 21c, why would it even need the AC for that? The MCU certainly doesnt get hot enough to need it.

Can anyone else confirm if their car is doing the same thing? that AC (or heater, or whatever was last left on "Auto" before you parked the car) just somehow comes on by itself minutes after you walk away from the car when Sentry is on?

Sentry mode is not what is consuming the extra power. The power loss comes from the Tesla Model Y remaining in Standby mode instead of entering Sleep mode. In Standby mode the power consumption is ~230W continuous, roughly 1kWh every 4 hours and 6kWh over 24 hours. When the Tesla Model Y is able to enter Sleep mode the high voltage battery is disconnected and all of the systems shut down except for the LTE and BT modems, also the electric door locks, key card reader and the vehicle alarm (not Sentry mode.) In Sleep mode the power use is ~25W or roughly 1/10th as much as when in Standby mode. Whenever Sentry mode is active the Tesla Model Y remains in Standby mode, never enters Sleep mode.

 

[lonertic]

The power loss comes from the Tesla Model Y remaining in Standby mode instead of entering Sleep mode.

Yeah but think about it tho, what's "sleep mode"? Cos in engineering terms, the loss (or draw) is the sum of parasitic drain. We know this can't be due to battery cell balancing as that's a resistive balancing strategy and happens whether the HV contactors are open or closed. So what is actually running in "standby mode" to warrant a 230w current draw? In a car that's extremely optimised for power usage, 230w is a huge number! As i said the MCU itself can only account for a very small fraction of that. Simply writing it off as "standby mode" without understanding what's involved in that "mode" and what's actually consuming the power is not an answer. Hence my theory, the only thing that can explain a high current draw like 230w is actually the HVAC system. The sum of all other computing resources, even at high CPU usage, even if you include wifi, bt, LTE, cameras, would be at most around 50-60w's which is already 10x more than what a dedicated multi-ch dashcam system would draw. So where's the rest of the energy going? Aren't you at least curious? Or are you just happy with the generic vague Tesla service tech answer like "oh it's a standby mode"?

 

[jcanoe]

Yeah but think about it tho, what's "sleep mode"? Cos in engineering terms, the loss (or draw) is the sum of parasitic drain. We know this can't be due to battery cell balancing as that's a resistive balancing strategy and happens whether the HV contactors are open or closed. So what is actually running in "standby mode" to warrant a 230w current draw? In a car that's extremely optimised for power usage, 230w is a huge number! As i said the MCU itself can only account for a very small fraction of that. Simply writing it off as "standby mode" without understanding what's involved in that "mode" and what's actually consuming the power is not an answer. Hence my theory, the only thing that can explain a high current draw like 230w is actually the HVAC system. The sum of all other computing resources, even at high CPU usage, even if you include wifi, bt, LTE, cameras, would be at most around 50-60w's which is already 10x more than what a dedicated multi-ch dashcam system would draw. So where's the rest of the energy going? Aren't you at least curious? Or are you just happy with the generic vague Tesla service tech answer like "oh it's a standby mode"?

The Tesla's computers are running when the Model Y is in Standby mode, ready for you to start driving. The high voltage contactors are closed and the power control system (PCS) is providing all of the low voltage power that may be required. (There are voltage conversion losses, some heat generated by the PCS.) The cameras are always powered on when in Standby mode (ready for Dashcam recording). The Climate Control system would only be active if preconditioning was happening either by manually turning on the Climate Control from the app or if Scheduled Departure Preconditioning was active. If Cabin Overheat Protection (COP) is set to be on (for the 1st 12 hours after the Tesla Model Y is parked), COP may run the just HVAC fan or the AC compressor too if COP with AC is selected. In addition, valves may open and close and pumps turn on to circulate coolant.

 

[lonertic]

The Tesla's computers are running when the Model Y is in Standby mode, ready for you to start driving. The high voltage contactors are closed and the power control system (PCS) is providing all of the low voltage power that may be required. (There are voltage conversion losses, some heat generated by the PCS.) The cameras are always powered on when in Standby mode (ready for Dashcam recording). The Climate Control system would only be active if preconditioning was happening either by manually turning on the Climate Control from the app or if Scheduled Departure Preconditioning was active. If Cabin Overheat Protection (COP) is set to be on (for the 1st 12 hours after the Tesla Model Y is parked), COP may run the just HVAC fan or the AC compressor too if COP with AC is selected. In addition, valves may open and close and pumps turn on to circulate coolant.

Thanks but see my earlier comment. I don't think it was COP in my case, as I said it was 21°c in my garage at 11pm, i didn't manually turn on the AC, so why was AC (or at least the fan) running on its own when nothing on the app or screen indicates it should be? I understand the DC-DC converter and accept there'll be some conversion losses, but it still doesn't add up. I'm just asking if anyone else have noticed their car turning on the cabin fan/AC by itself whilst Sentry was on

 

[Rocky_H]

Point by point:

So what is actually running in "standby mode" to warrant a 230w current draw?

The entire high power full self driving computer.

In a car that's extremely optimised for power usage, 230w is a huge number!

But it WAS NOT optimized for this use case! This scenario of having to use the entire powerful self driving computer with its redundant processors being on, just to run dashcams is something the cars were NEVER designed for, and so is very inefficient. To borrow a phrase from an old Garfield comic: "It's like swatting a fly with a Buick."

As i said the MCU itself can only account for a very small fraction of that.

...which is wrong.

Simply writing it off as "standby mode" without understanding what's involved in that "mode" and what's actually consuming the power is not an answer.

It is the answer, because it is understood. This has been looked at and has been this way for quite a long time.

The sum of all other computing resources, even at high CPU usage, even if you include wifi, bt, LTE, cameras, would be at most around 50-60w's

If you wanted to run those things from a Chromebook motherboard--sure. It could be low power. But it's not that. This is using the main, super high performance, decision making self driving computer. That is high performance and high power consumption, which was kind of OK, because its intended use was to only be on while driving. The original design parameter was that it would then be able to power off and save that energy while the car was parked.

It was only later, after the car was out, that customers started demanding that Tesla use the cameras that already existed to create an ad-hoc "dashcam" functionality it was never meant for. And the only way, using the existing hardware, was that it had to use the power hungry main computer and keep it on all the time.

which is already 10x more than what a dedicated multi-ch dashcam system would draw.

Of course, because that is a different design project with different requirements. If you are beginning with trying to design a low power system that is JUST for a dashcam, then that is easy to do so. But if you're trying to retrofit a bicycle to be used as a submarine, it's going to be terrible at that.

So where's the rest of the energy going? Aren't you at least curious? Or are you just happy with the generic vague Tesla service tech answer like "oh it's a standby mode"?

It's known, and that's the true information.