Where's the missing 10 kwh energy use from today?

[paulchou]

New LR owner here. So this morning I unplugged the charger, left the house at 7:30am with 80% charge, drove for about 33 miles, with Tesla trip app showing avg energy use of 314wh/mi and total energy use of 10kwh (see below). At 11:30pm I noticed the battery is down to ~60% so I plugged in the charger. But something doesn't seem to adde up ...given the LR battery size of 100kwh, shouldn't I have ~70% battery left?

And as you can see from the other picture below, I just added 75 miles or ~18.5%, assuming 405 miles range at 100kwh - this would be consistent with the ~60% battery level I saw before the latest charging session. But why 18.5% drain?!? Why is it not 10% drain since the 33 miles only used 10kwh? Sure I don't expect everything to match exactly and I am ok w/ a couple % off here and there - but ~10% off?

The only other thing I can think of is the car did park outside for ~5 hrs, in mid 30s temperature, and perhaps the kw/mi calculation only counts when you are moving? But still, losing 8-9% battery (or ~10kwh) just for parking outside in cold weather for not even half a day? Phantom drain can't be this excessive can it?

FYI when I was driving I had heater off but did turn on heated seats and heated yoke - but that should be reflected in the 314wh/mi number right? When the car is parked sentry is on, FWIW.

What am I missing here?

 

[ucmndd]

When the car is parked sentry is on, FWIW.

What am I missing here?

1) Not all of the battery is available to you for propulsion, so basing math on a 100kwh battery is not gonna work. I think it’s closer to 95kwh useable.

2) Sentry mode uses fantastic amounts of energy. A good ~2kwh during those 5 hours you spent parked.

 

[Rocky_H]

What am I missing here?

Two things:
The sentence above says you had sentry on. That uses a huge amount of energy, since it will never allow the car to go to sleep while it parked.
And then the other thing is this one:

perhaps the kw/mi calculation only counts when you are moving?

That's exactly right. It only turns on that counter while the car is in Drive or Reverse. So all of that time while parked and using large amounts of energy in sentry will not show up in that display.

 

[paulchou]

Two things:
The sentence above says you had sentry on. That uses a huge amount of energy, since it will never allow the car to go to sleep while it parked.
And then the other thing is this one:

That's exactly right. It only turns on that counter while the car is in Drive or Reverse. So all of that time while parked and using large amounts of energy in sentry will not show up in that display.

Lesson learned. Still trying to optimize battery efficiency. I've been very stingy w/ AC/Heater usage but as it turns out Sentry plays a much bigger role?

I used to pre-condition my car every morning but I hate the fact that pre-conditioning also blasts the AC/Heater ...wish there's a way to do just the pre-conditioning of the battery w/o turning on climate control.

 

[ucmndd]

There’s really no reason to precondition the battery unless you fear you’re going to be short on range to get where you need to go. Certainly not if efficiency is your goal - energy from the wall counts too and heating a battery while it sits is rarely if ever going to be a winning proposition.

 

[airborne spoon]

There’s really no reason to precondition the battery unless you fear you’re going to be short on range to get where you need to go. Certainly not if efficiency is your goal - energy from the wall counts too and heating a battery while it sits is rarely if ever going to be a winning proposition.

Sort of. For example when i drive from NV to So-Cal the first 2 hours of the trip are super cold usually when i leave its about 10f and there is a few paces along the road where its gotten down to -15f with an average of -7f. So by preheating the battery before i leave (while its still plugged in to a HPWC @80A) it saves a crapton of power over the trip. The heater obv still kicks in but its not for a while and as long as i keep my speed up or goose the throttle a few times to pass a flatlander it doesn't have to work too hard, thus saving a lot of juice over the first leg of my trip every month.

Some figures I've noted over a couple years of taking this trip: if i don't preheat the battery i can only skip 1 SC, if i preheat i can skip 2 SC. Putting the car on range mode regardless of preheating the pack will not allow me to skip 2 SC since the range mode tends to use more power than when its off.

 

[ucmndd]

Sort of. For example when i drive from NV to So-Cal the first 2 hours of the trip are super cold usually when i leave its about 10f and there is a few paces along the road where its gotten down to -15f with an average of -7f. So by preheating the battery before i leave (while its still plugged in to a HPWC @80A) it saves a crapton of power over the trip. The heater obv still kicks in but its not for a while and as long as i keep my speed up or goose the throttle a few times to pass a flatlander it doesn't have to work too hard, thus saving a lot of juice over the first leg of my trip every month.

Some figures I've noted over a couple years of taking this trip: if i don't preheat the battery i can only skip 1 SC, if i preheat i can skip 2 SC. Putting the car on range mode regardless of preheating the pack will not allow me to skip 2 SC since the range mode tends to use more power than when its off.

Right, this is basically what I said. You're pre-purchasing some range and trip efficiency by sucking ~5kw from the wall for a half hour or so before you leave. It can be a good strategy for a trip, if you need the range. But doing it every day to optimize "battery efficiency" doesn't make a lot of sense. You're just taking power from one place to save it somewhere else, usually at a net loss in terms of efficiency.

 

[paulchou]

Right, this is basically what I said. You're pre-purchasing some range and trip efficiency by sucking ~5kw from the wall for a half hour or so before you leave. It can be a good strategy for a trip, if you need the range. But doing it every day to optimize "battery efficiency" doesn't make a lot of sense. You're just taking power from one place to save it somewhere else, usually at a net loss in terms of efficiency.

Good info. So much to learn here. So obviously at 30f or below, it make sense to pre-condition the battery, if maximizing range is the goal. I wonder at what temperature on the other extreme that would make sense to pre-condition for maximum range. >90f?

Lastly, unlike ICE cars, where I can park in a garage for weeks or even months and still have some gas when I return, it seems I can't do that with a Tesla as the battery drains out much faster. Has anyone actually tried a hard shutdown on the vehicle to save battery on extended leave - or would that even work, as in would the door even lock after hard shutdown?

 

[ucmndd]

Good info. So much to learn here. So obviously at 30f or below, it make sense to pre-condition the battery, if maximizing range is the goal. I wonder at what temperature on the other extreme that would make sense to pre-condition for maximum range. >90f?

There’s no need to “cool” the battery via preconditioning in the hot if that’s what you’re asking. The cabin on the other hand… cool that sucker down!

Lastly, unlike ICE cars, where I can park in a garage for weeks or even months and still have some gas when I return, it seems I can't do that with a Tesla as the battery drains out much faster. Has anyone actually tried a hard shutdown on the vehicle to save battery on extended leave - or would that even work, as in would the door even lock after hard shutdown?

If you’re leaving your car for an extended period of time, do what the manual says and plug it in. It will charge when it needs to and take care of itself. Easy peasy.

Left alone in your garage, with sentry mode, summon standby, and cabin overheat protection turned off, you should lose very little energy - like 1% a day or less. If you’re parking away from home, say an airport or something like that, you’ve got weeks and weeks before it’s an issue, provided you turn off all the energy sucking “features” and have the discipline to leave the car alone and not check it via the app 5 times a day.

 

[Rocky_H]

I wonder at what temperature on the other extreme that would make sense to pre-condition for maximum range. >90f?

There’s no need to “cool” the battery via preconditioning in the hot if that’s what you’re asking. The cabin on the other hand… cool that sucker down!

I might fine tune this answer a little bit regarding hot temperatures. It's not something you would do with manually turning on pre-conditioning, but if you have access to plug the car in when the car has gotten extremely hot, like over 100 degrees, then go ahead and plug it in. It may spin up the cooling system and use the air conditioner to chill the coolant some to bring the battery temperature down. I have observed this in my car when it sat out in the parking lot all day on the blacktop at 103 degrees and then I get home. It sounds like it shuts down, but then when I get the cable and plug it in, I hear it start up the air conditioner and blowing out the radiators in the front to actively cool the battery.

People have been able to read the signals in the car with 3rd party tools, and here's what's going on. The car has an allowed high and low temperature target. It will leave that allowed range a bit larger when the car is not plugged in so it doesn't have to deplete your energy you might need for driving. But when it gets plugged in, so it has access to an extra energy source, then it brings in those target temperatures a little bit so it will use the systems to bring the battery to a little better temperature state.

 

[paulchou]

Thanks @Rocky_H , @ucmndd @airborne spoon

One thing that gives me a lot of appreciation is that given the EPA figure of 33.7 kWh is roughly the energy equivalent of 1 gallon of gas - it implies at full charge the LR has less than 3 gallons of gas worth of energy. This compares to Mercedes s500, which is similar in weight, that has 500+ range, but has a 21 gallon tank. My imprecise math tells me S LR is at least 5x more efficient, w superior acceleration, quieter, and is more fun to drive (subjective).

The downside of that is everything type of energy usage matters as they are proportionally more significant than ICE counterparts. Things that I used to take for granted, like AC, heating, security functions, or even checking it on the app, could have an outsized impact.

Last question: how much does the aero wheel cover matter? I've seen one-off tests that suggest taking it off will reduce range b/w 3-7%? Also it seems it's speed dependent - the faster you go, the more aero cover helps?

 

[David_Cary]

I would think 3% is a better part of that range for the aero covers. Speed matters absolutely. Aero resistance is not linear and it isn't even squared but closer to 3rd power. Nothing is exact of course but very dramatically goes up with speed. So the aero effect is much greater at 80 mph than 60 mph and there is probably near negligible effects at 30 mph.
It isn't truly fair to compare gas and electricity when it comes to efficiency. They aren't really the same. Gas (or any fossil fuel) has to be used to generate heat that then generates propulsion so there has to be losses. Electricity generation had those losses already. So, yes an EV is more efficient but it isn't fair to negate the generation efficiency issues (or transmission or charging) either.
Note that a/c is a relatively minor energy need compared to heat. Security functions wouldn't be so much if Tesla wasn't so bad at accessory efficiency. That being said, an ICE car doesn't have these things (sentry mode) partly because they don't have a large battery to allow it.
Also note that a cold battery will appear to have less stored energy because of temperature effects. That energy isn't lost, it is just temporarily inaccessible.
One thing you will realize also is that air resistance goes down signficantly with heat. Often more than the a/c uses. I find my range is quite high at 95 degrees out with the a/c on at high speeds.

 

[BostonBurley]

New LR owner here. So this morning I unplugged the charger, left the house at 7:30am with 80% charge, drove for about 33 miles, with Tesla trip app showing avg energy use of 314wh/mi and total energy use of 10kwh (see below). At 11:30pm I noticed the battery is down to ~60% so I plugged in the charger. But something doesn't seem to adde up ...given the LR battery size of 100kwh, shouldn't I have ~70% battery left?

And as you can see from the other picture below, I just added 75 miles or ~18.5%, assuming 405 miles range at 100kwh - this would be consistent with the ~60% battery level I saw before the latest charging session. But why 18.5% drain?!? Why is it not 10% drain since the 33 miles only used 10kwh? Sure I don't expect everything to match exactly and I am ok w/ a couple % off here and there - but ~10% off?

The only other thing I can think of is the car did park outside for ~5 hrs, in mid 30s temperature, and perhaps the kw/mi calculation only counts when you are moving? But still, losing 8-9% battery (or ~10kwh) just for parking outside in cold weather for not even half a day? Phantom drain can't be this excessive can it?

FYI when I was driving I had heater off but did turn on heated seats and heated yoke - but that should be reflected in the 314wh/mi number right? When the car is parked sentry is on, FWIW.

What am I missing here?

For me, 265 miles per charge is more like 215 actual miles, tops. Tesla distance is vastly overrated.