Vampire Drain/Loss Tracking

[AlanSubie4Life]

The first paragraph of “Battery Care” on that page says approximately 1% per day discharge, and even gives an example of leaving a car unplugged at an airport for two weeks and having approximately 14% discharge. How is that “not quantified, for obvious reasons”? I think your obsession about the vampire drain is blinding you to Tesla actually giving a number and cautioning people about it.

You are correct. I have read this page before, but when I glanced this morning didn’t read that far (read down to that paragraph).

I stand corrected; it absolutely is quantified. Kudos to Tesla for that, I guess. I know Tesla is brilliant and all, but I would really like to be able to control the drain in certain situations (see above), and I would like it to be better in general.

I have a hard time believing that an average drain of 20-40W does anything significant for HV battery maintenance (though that is what Tesla says it is doing!). Obviously might maintain the AGM battery with the battery float charger due to all the parasitic loads on it. So in that sense it is battery maintenance - but that’s not what we really care about (someone elsewhere posted that 12V battery maintenance is better on the 3 (and includes an always-connected float charger to reduce contactor wear???) so that is good, though I have not seen the source).

Re: Obsession - I suppose you could make the argument that I am obsessed. But actually I just want to understand it, and I don’t take everything Tesla says at face value.

 

[Daniel in SD]

I have a hard time believing that an average drain of 20-40W does anything significant for HV battery maintenance (though that is what Tesla says it is doing!).

Maybe they used to claim this but they now admit that it is to "power the onboard electronics."
Have to keep those ultrasonic sensors ready to go!

 

[AlanSubie4Life]

Actually, after reading page 122 carefully, Tesla does not claim the

Maybe they used to claim this but they now admit that it is to "power the onboard electronics."
Have to keep those ultrasonic sensors ready to go!

Yeah, I reread this (carefully this time, parsing every turn of phrase!) and you are right, they say nothing about HV battery maintenance. I got the “HV battery maintenance” info from this forum - my mistake!!! Tesla is clear it is specifically for powering on board electronics. The only mention is that when plugged in it will maintain a charge level for maximum battery longevity. Which is not battery maintenance (it’s only needed due to the drawdown of the HV due to the electronics). As mentioned earlier, using the battery is likely worse for the HV battery as compared to no drain (only self discharge). Though the effect is relatively small, equivalent to about 1000 extra battery miles per year....

On the ultrasonic sensors - odd...this morning they were not warm when the car was sleeping. Which is good I guess. I’ll try to figure out the pattern.

 

[omgwtfbyobbq]

Actually, after reading page 122 carefully, Tesla does not claim the


Yeah, I reread this (carefully this time, parsing every turn of phrase!) and you are right, they say nothing about HV battery maintenance. I got the “HV battery maintenance” info from this forum - my mistake!!! Tesla is clear it is specifically for powering on board electronics. The only mention is that when plugged in it will maintain a charge level for maximum battery longevity. Which is not battery maintenance (it’s only needed due to the drawdown of the HV due to the electronics). As mentioned earlier, using the battery is likely worse for the HV battery as compared to no drain (only self discharge). Though the effect is relatively small, equivalent to about 1000 extra battery miles per year....

On the ultrasonic sensors - odd...this morning they were not warm when the car was sleeping. Which is good I guess. I’ll try to figure out the pattern.

I think the "system tests" Tesla refers to include periodically evaluating the pack cells to collect information that helps with balancing/use/lifespan.

https://www.mdpi.com/1996-1073/10/3/404/pdf

Your trusty Spark EV doesn't need to do when the car is off because it has 26ah cells connected in 2p96s (p = parallel, s = series), which is fairly straightforward to balance/manage. The 3 has 5ah cells connected in 46p96s and requires more attention to balance/manage. The advantage Tesla has by using smaller cells is lower cost compared to using larger cells.

 

[Daniel in SD]

I think the "system tests" Tesla refers to include periodically evaluating the pack cells to collect information that helps with balancing/use/lifespan.

https://www.mdpi.com/1996-1073/10/3/404/pdf

Your trusty Spark EV doesn't need to do when the car is off because it has 26ah cells connected in 2p96s (p = parallel, s = series), which is fairly straightforward to balance/manage. The 3 has 5ah cells connected in 46p96s and requires more attention to balance/manage. The advantage Tesla has by using smaller cells is lower cost compared to using larger cells.

I don’t think this is true. My understanding is that most of the power used is from the 12V system. That’s why the Teslas eat 12V batteries every couple years.
Also I’m pretty sure that paper describes a cell balancing system that is used when drawing power from the battery. Why would you charge a battery pack and then start moving power between cells? That seems like a good way to waste power and lower the lifetime of your pack.

 

[omgwtfbyobbq]

I don’t think this is true. My understanding is that most of the power used is from the 12V system. That’s why the Teslas eat 12V batteries every couple years.
Also I’m pretty sure that paper describes a cell balancing system that is used when drawing power from the battery. Why would you charge a battery pack and then start moving power between cells? That seems like a good way to waste power and lower the lifetime of your pack.

AFAIK, 12V lifespan is just a function of how much the car does with the 12V in the background. My old Prius would go through batteries more often than my other cars because of the smart key system, and I imagine the S/3/X go through 12V batteries faster than a Prius because they have smart key and/or phone key, a connected modem, a more active BMS (thermal and charge), and so on.

From what I've gathered about Tesla's BMS, it doesn't balance cells/strings most of the time the car is parked, although it can in certain circumstances. I'm guessing it does periodically test/monitor the strings to gather more information about their condition, and since there are already always on systems draining the 12V anyway, topping off the 12V periodically also allows for some time to monitor the pack's condition and potentially run some other tests.

Tesla could go with larger individual cells to get around this, but that would increase costs substantially and there would still likely be significant stand-by energy use because of the other features the car has.

 

[TW14 9LF]

Left my car in my garage for a bit over a week over the holiday break. I left the car plugged in. I charged to 90% before I left, so I had 278 miles remaining. Before I left, I decreased the charge level to 50%. When I got home, I had 231 miles left. I woke the car up remotely through the app three times while I was gone. I left the car on Thursday evening, returned the following Saturday morning, 8 1/2 days total. So, a bit over 5 miles per day lost to vampire drain.

Interestingly, my previous EV, a Ford Focus Electric, would show no appreciable degradation in range or percent charge over much longer times than this. That's a good thing, since the car only had about 70 miles range to begin with. So, 5+ miles per day on a car with 300 miles range is likely acceptable, whereas it would be a real killer in a car with such small range. But have to wonder what Ford was doing different than Tesla to better manage vampire drain.

Keith

 

[gemee]

Yes, that seems to be about what most of us are experiences w/ those weather conditions. It's pretty well documented in the last 7 pages. I can only highly recommend setting up a way to charge at your home if you can. We didn't have it installed yet when we first got ours and what a PITA it was. And the latest from Elon/Tesla is to charge your battery to 80-90%, or higher on a regular basis. it is now recognized that poor battery calibration will continue/worsen if you only charge to the previously recommended 50-60%.

Tesla's New Stance On Charging Habits + Elon Responds: Video

Thanks for sharing judyjetson!
Being a noob, I didn't think how much/how often I (super)charge the Model 3, would affect its retention capacity (but of course, it makes sense that it should). Still somewhat confused about the ideal SoC for preserving battery range (85%? 90%?), and whether or not to SuperCharge. Manual says "The peak charging rate of the Battery may decrease slightly after a large number of DC Fast Charging sessions, such as those at Superchargers."

Will definitely get a charging solution, when it becomes feasible - but for now, parking at home is in a garage, with no accessible electric outlets :-/

 

[TexasEV]

Charge to whatever you want to up to 90% (and 100% for trips) and supercharge when you need to. The battery will be just fine.

 

[misujerr]

Phew, just read all eight pages, because mine lost seven miles last night (~50 degrees F.) Mostly been 3 - 4 miles/night so I'll monitor. What I wanted to comment on was that little gem posted a couple comments up above from the "Like Tesla" vid. Man, I'm confused now. Charge to 90% every night? I don't drive that much on a daily basis (maybe 30 miles) so it won't go down very far. Then once in a while drive it down to 5-10%. All at once or can it be over days? I don't drive to Santa Barbara that often! (300 mile for me If over days, charge it nightly while adjusting charge point to "charge complete" every night? My original intent before this was to charge it up, then drive it over days till it was low, then charge up again. But ABC - always be chargin' as they say in the Volt community. And along those lines, my poor Volt lives outside now and like Subie's Spark, hardly has any vampire drain.

 

[jombolo]

Phew, just read all eight pages, because mine lost seven miles last night (~50 degrees F.) Mostly been 3 - 4 miles/night so I'll monitor. What I wanted to comment on was that little gem posted a couple comments up above from the "Like Tesla" vid. Man, I'm confused now. Charge to 90% every night? I don't drive that much on a daily basis (maybe 30 miles) so it won't go down very far. Then once in a while drive it down to 5-10%. All at once or can it be over days? I don't drive to Santa Barbara that often! (300 mile for me If over days, charge it nightly while adjusting charge point to "charge complete" every night? My original intent before this was to charge it up, then drive it over days till it was low, then charge up again. But ABC - always be chargin' as they say in the Volt community. And along those lines, my poor Volt lives outside now and like Subie's Spark, hardly has any vampire drain.

According to that article i posted, it seems to be the way to software read's available power and higher charging allows for better calibration. The M3 manual also strongly encourages ABC, "The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it." Bold and caps! hah

 

[jombolo]

AFAIK, 12V lifespan is just a function of how much the car does with the 12V in the background. My old Prius would go through batteries more often than my other cars because of the smart key system, and I imagine the S/3/X go through 12V batteries faster than a Prius because they have smart key and/or phone key, a connected modem, a more active BMS (thermal and charge), and so on.

From what I've gathered about Tesla's BMS, it doesn't balance cells/strings most of the time the car is parked, although it can in certain circumstances. I'm guessing it does periodically test/monitor the strings to gather more information about their condition, and since there are already always on systems draining the 12V anyway, topping off the 12V periodically also allows for some time to monitor the pack's condition and potentially run some other tests.

Tesla could go with larger individual cells to get around this, but that would increase costs substantially and there would still likely be significant stand-by energy use because of the other features the car has.

can someone point me to any info in the manual that talks about the 12v battery? I read somewhere that the 12v battery keeps the electronics powered which is why you are still able to enter/exit vehicle if the HV battery were to be completely drained. This made me always think this was the cause of periodic vamp drain - the HV battery periodically charging the 12v battery when it reaches a low charge. you are also able to connect a 9v battery through the front bumper service pop-out to open the frunk (and perhaps the door, but cannot remember). I couldn't find really any info in the manual about the 12v battery but perhaps was just completely looking in the wrong sections.

 

[Daniel in SD]

can someone point me to any info in the manual that talks about the 12v battery? I read somewhere that the 12v battery keeps the electronics powered which is why you are still able to enter/exit vehicle if the HV battery were to be completely drained. This made me always think this was the cause of periodic vamp drain - the HV battery periodically charging the 12v battery when it reaches a low charge. you are also able to connect a 9v battery through the front bumper service pop-out to open the frunk (and perhaps the door, but cannot remember). I couldn't find really any info in the manual about the 12v battery but perhaps was just completely looking in the wrong sections.

That’s the reason the 12V battery doesn’t last very long. All the cars systems, except for the drive unit, run off of 12V. It disconnects the HV battery when the car is asleep (that’s the loud clunk you can hear) and then reconnects it after vampire drain depletes the 12V.

 

[AlanSubie4Life]

The 12V battery is covered on page 18 and page 122 of the manual. (Specifically says energy is used to recharge the 12V, but no surprises there...)

However, there's a claim that there is an always-on battery tender for the 12V battery on the Model 3. @scottm made this claim; I am not sure exactly where he got the information from, or whether this has been verified. I didn't see it in the partial parts diagram we have access to.

As a general comment, aside from the longevity of the battery, it doesn't really matter whether the supply for the vampire load is the HV or the 12V. The issue is where that energy is going.

Both 12V and lithium-ion batteries have very low self discharge (Li-ion about 1% per month), so if the electronics weren't drawing anything, self-discharge wouldn't be an issue, so it wouldn't matter if the HV battery was used to trickle charge the 12V (wouldn't take any significant energy). I don't think anyone would be too surprised or complain if they came back to their car after 6 months and it had 20 fewer miles than when they left it...

 

[omgwtfbyobbq]

can someone point me to any info in the manual that talks about the 12v battery? I read somewhere that the 12v battery keeps the electronics powered which is why you are still able to enter/exit vehicle if the HV battery were to be completely drained. This made me always think this was the cause of periodic vamp drain - the HV battery periodically charging the 12v battery when it reaches a low charge. you are also able to connect a 9v battery through the front bumper service pop-out to open the frunk (and perhaps the door, but cannot remember). I couldn't find really any info in the manual about the 12v battery but perhaps was just completely looking in the wrong sections.

There isn't a lot in the manual, but the 12V does power the always on bluetooth/key, cell modem, processor that powers all of these things, and whatever other stuff runs periodically (probably the BMS to at least monitor the cell strings from time to time). The system will wake up the HV battery periodically to recharge the AGM lead acid and probably run diagnostics.

Syonyk's Project Blog: Tesla Model S 12V Battery Analysis

The lead acid doing 2+ cycles/day is why Tesla needs an expensive AGM battery and why vampire drain is a little less than a mile per day in the long run. Parking the car indoors (no cabin cooling), turning off remote access, and turning off bluetooth devices might reduce that.

 

[BestHand]

There isn't a lot in the manual, but the 12V does power the always on bluetooth/key, cell modem, processor that powers all of these things, and whatever other stuff runs periodically (probably the BMS to at least monitor the cell strings from time to time). The system will wake up the HV battery periodically to recharge the AGM lead acid and probably run diagnostics.

Syonyk's Project Blog: Tesla Model S 12V Battery Analysis

The lead acid doing 2+ cycles/day is why Tesla needs an expensive AGM battery and why vampire drain is a little less than a mile per day in the long run. Parking the car indoors (no cabin cooling), turning off remote access, and turning off bluetooth devices might reduce that.

Great data. Actually, I believe that losses of DC2DC are very small, so I would leave (I was sure that it was always on) DC2DC always on as it was suggested in the article. It would not make vampire drain less, but will prolong 12V battery life.

 

[AlanSubie4Life]

little less than a mile per day in the long run.

Well, 1% a day...(3-4 miles).

 

[Magnets!]

So if I am plugged in, will the 12v get charged from 'shore power' or the HV battery?

 

[BestHand]

So if I am plugged in, will the 12v get charged from 'shore power' or the HV battery?

It will be charged of HV battery, but it does not matter really, all energy comes of your outlet anyway.

 

[Magnets!]

Correct, but with TOU plan, when it comes out of the outlet makes a difference. There appears to be some draw on the shore power though aside from HV charging, perhaps for the wifi and bluetooth radios as well as various pumps, circuit boards for BMS, etc. But at least the 12v charging is coming from the HV battery.