M3 MR vs Chevy Bolt (energy consumption)

[ℬête Noire]

But I could not do that when my windshield was dirty (it fogged up a lot).

Maybe that's partially it, too? My windshield is currently in a state of "never entirely clean" because of the squares on the inside from manufacturing issue. Those spots start fogging much sooner than the rest of the window. Once the SC gets that detailed out, hopefully this week, perhaps I'll try again.

 

[AlanSubie4Life]

Some Tesla rando giving you the brush-off because they see a 1kWh/day

It's Tesla that says this (actually 750Wh/day), not some Tesla rando. The datapoint I quoted was from a friend who went to India for 3 weeks over the holidays. It was an experiment we did (for science!). I trust her numbers, especially since they're exactly what Tesla says to expect.

It absolutely is a meaningful portion of "vampire drain", AKA the card doing stuff when you're not driving it.

We're talking about two things: 1) Car doing stuff when you're not driving it (This is definitely happening) and 2) Car is doing something miraculous to keep the battery/cabin temp at the perfect temperature (very questionable). I have not seen this second thing (I have cabin overheat turned off). I keep my car in a cool garage. Also, it would require enormous amounts of energy, relative to 30-40W, to keep the pack at the "optimal" temperature. Do the math on the thermal mass and heat transfer rate to the environment. It's just not physically reasonable that anything useful could be done with 30-40W. (For order of magnitude - how long does it take driving to get regen dots to go away on a cold battery, when the car might be drawing 14kW @ 60mph, and the waste heat (let's say 10%) is used to warm the battery. Maybe you can even use these order of magnitude numbers and plug it into the heat differential equation & Green's function to figure out what is reasonable Heat equation - Wikipedia.) My point is it would require a lot of energy to do anything meaningful to the pack when parked. When it gets to very extreme temperatures, something may happen to prevent damage (I have not had to deal with this yet so cannot speak about it).

I encourage you, if you have an opportunity, to leave your car for 10 days in a climate-controlled garage (or at least, at a cool time of year), and report back. My guess is you'll find your numbers are in good alignment with what Tesla says.

 

[ℬête Noire]

It's Tesla that says this (actually 750Wh/day), not some Tesla rando. The datapoint I quoted was from a friend who went to India for 3 weeks over the holidays. It was an experiment we did (for science!). I trust her numbers, especially since they're exactly what Tesla says to expect.

5 miles in 4 days is what I saw. So what was the differences? "For science".

Slightly colder outside (but without direct sun this shouldn't be at a range that'll make a difference). No WiFi connection. Does she have cabin protection on? I have it turned off.

EDIT: I assume she had it unplugged like I did?

 

[AlanSubie4Life]

5 miles in 4 days is what I saw. So what was the differences? "For science".

Slightly colder outside (but without direct sun this shouldn't be at a range that'll make a difference). No WiFi connection. Does she have cabin protection on? I have it turned off.

One difference is that it was 4 days and not 21 days. Big difference. Forget the averages...initial conditions may matter a lot.

She may have cabin protection on. But it was ~50-70 degrees in a garage in San Diego while she was gone. So can't imagine that would be a factor.

WiFi may be a factor - for sure it uploads data to the cloud over WiFi.

5 miles in 4 days is a good result and well below what Tesla says to expect. If I have an opportunity to do a longer experiment I guess I can provide the data (change my password, etc.). I could easily do it, but then I'd have to drive my silly Spark EV around and my wife would wonder what the heck is wrong with me.

 

[ℬête Noire]

She may. But it was ~50-70 degrees in a garage in San Diego while she was gone. So can't imagine that would be a factor.

I haven't looked at it recently but my recollection of the behavior people saw when it first came out is it could very well be a factor in not entering deep sleep. Because the code assumes it's been told to keep a closer watch on temp, it'll not go into deepest sleep, or at least pop out of it more often. ¯\_(ツ)_/¯

5 miles in 4 days is a good result and well below what Tesla says to expect.

Perhaps a KISS messaging choice so they don't get pestered by throngs of people running entirely typical configurations that, while that technically somewhat sub-optimal configuration choices for vamp drain, still produce entirely acceptable results?

I could easily do it, but then I'd have to drive my silly Spark EV around and my wife would wonder what the heck is wrong with me.

LOL Well you'd also need to turn off the phone BT. Maybe unpairing it would be enough?

 

[AlanSubie4Life]

Looks like a significant contributor to the difference is that Bolt's on-board charger may be more efficient?

So for Chevy Bolt:
Total Distance: 1187 miles
Energy Consumption Per Car: 253 kWh (0.2125 kWh/mile)
Energy Consumption Per Charger: 270.86 kWh (0.2280 kWh/mile)

So this implies minimum efficiency of Bolt on-board charger for this user is 93% (assuming car meter is correct of course).

The Tesla in-car data is garbage, so we can't trust it, but it looks like the API data from users in this thread & elsewhere is implying 87% charger efficiency. But we need more carefully gathered real-world data.

Anyone measure difference between wall (actual) and Tesla kWh reporting?

In any case that would be a big difference, unless I am missing some factor here.

EDIT: The 87% number is fairly consistent with the EPA range numbers, battery size, and "fueling" costs, though, so it probably checks out. But anyway more data would be good.

For example, AWD is 310 EPA miles, 29kWh/100 EPA miles, so that's 89.9kWh to charge a 75kWh pack. So that's 83% efficient. I know there is some fudging of the numbers a bit (particularly the LR RWD), but all the numbers come in around this point (for LR RWD it's 334 EPA miles * 26kWh/100 EPA miles = 87kWh => 86% efficient). Take all this with a grain of salt because there are a lot of layers to the EPA methodology - it's a lot easier to just measure yourself...

 

[omgwtfbyobbq]

The window sticker is supposed to be wall to wheel. How would you get a range of 310 miles with 270Wh/mi usage and a 75kwh battery? It includes charging losses.
The baseline vampire drain in ideal circumstances is 30-40W. That’s way more than should be required for OTA updates cellular and Bluetooth (my iPhone has a 30mW standby power!). I’m just saying that cars with the same MPGe should have similar energy costs for the average user. Right now unless you drive the EPA test 24/7 the Model 3 will use more electricity despite having a better rating. Anyway I should really take it up with the EPA instead of arguing with people on a forum.

The baseline drain in ideal circumstances is likely well below that, like in this example (<75Wh/day).

The ‘vampire drain’ reference place

Someone can also see much higher rates with cabin overheat protection, a third party app, a battery that the car thinks needs balanced, a wifi update that can't DL, and I imagine other circumstances, but those are all transitory and can be handled. The car's range being a function of the SOC calculation further complicates things because it's a (weak) function of pack temperature.

 

[scaesare]

I think you're missing the point. Why does the number displayed on the dashboard matter if the total amount of electricity used to charge the battery is what you're actually paying for?

For me it matters because it's the amount of energy I can squeeze out of the pack on the road that determines how far I can go, or worse, if I might get stranded.

I honestly don't care about spending another $0.75 on electricity in my garage over night if I can travel farther on the road.

 

[Daniel in SD]

For me it matters because it's the amount of energy I can squeeze out of the pack on the road that determines how far I can go, or worse, if I might get stranded.

I honestly don't care about spending another $0.75 on electricity in my garage over night if I can travel farther on the road.

For that you should use the energy display, there is no gauge on the car that tells you how many kWh are left in the pack.
My point was that the comparison of the kWh/mi readings of different cars is pointless. It sounds like what you care about is range (which is important!). But if you’re talking about efficiency (how far you can go on 1kwh) that has to be measured from the wall.

 

[Daniel in SD]

The baseline drain in ideal circumstances is likely well below that, like in this example (<75Wh/day).

The ‘vampire drain’ reference place

Someone can also see much higher rates with cabin overheat protection, a third party app, a battery that the car thinks needs balanced, a wifi update that can't DL, and I imagine other circumstances, but those are all transitory and can be handled. The car's range being a function of the SOC calculation further complicates things because it's a (weak) function of pack temperature.

No one is getting 75Wh per day. Where did you get that number? It’s about 1kwh per day in ideal circumstances.

 

[AlanSubie4Life]

The baseline drain in ideal circumstances is likely well below that, like in this example (<75Wh/day).

The ‘vampire drain’ reference place

Someone can also see much higher rates with cabin overheat protection, a third party app, a battery that the car thinks needs balanced, a wifi update that can't DL, and I imagine other circumstances, but those are all transitory and can be handled. The car's range being a function of the SOC calculation further complicates things because it's a (weak) function of pack temperature.

Let me know if you can duplicate that remarkable result, because it is *well* below what Tesla says to expect.

I’m going to try some of these other things suggested (disable overheat protection, etc.), but doubt it will change my results much.

Any datapoint needs to be done over multiple days (> 5 ideally); gets rid of initial transients.

Edit: also as Daniel says, that reference (likely very abnormal or with confounding factors) is actually 286Wh/day, or a little over 10W. Would be a great start to consistently get that, but does not currently represent the norm.

 

[scaesare]

For that you should use the energy display, there is no gauge on the car that tells you how many kWh are left in the pack.

Correct. I never said otherwise.

My point was that the comparison of the kWh/mi readings of different cars is pointless.

I disagree. While driving, that's the number that indicates how efficiently the car will use the energy in my pack, minor inaccuracies aside.

It sounds like what you care about is range (which is important!). But if you’re talking about efficiency (how far you can go on 1kwh) that has to be measured from the wall.

Not quite. What I care about are both range and driving efficiency. I don't really care if I waste 11% of energy from the wall vs 7%. I care about how well the car will translate available energy from a full pack in to miles driven.

This is in the same way that I don't really care if one gas pump has a couple percentage points of error as compared to another... as long as the pump head clicks off, I know my tank is full, and at that point it's the efficiency of my engine that determines the range I'll have on the road.

 

[SageBrush]

It’s about 1kwh per day in ideal circumstances.

The last time I checked in my car over a week this winter it was about 20 watts

 

[SageBrush]

there is no gauge on the car that tells you how many kWh are left in the pack.

Divide 4 into miles remaining

 

[AlanSubie4Life]

there is no gauge on the car that tells you how many kWh are left in the pack.

Yeah, the miles remaining is kWh left in the pack, it just has strange units (as @SageBrush says just divide by about 4).

What I care about are both range and driving efficiency. I don't really care if I waste 11% of energy from the wall vs 7%. I care about how well the car will translate available energy from a full pack in to miles driven.

Fair enough - but there are people who will make decisions about very efficient gasoline cars based on a 5-10% difference in efficiency. So eventually for Tesla this might matter, if there are ever comparable vehicles. Getting back to the topic of this thread, to me INITIAL data suggests that the Bolt charger is much more efficient than the Model 3s - it accounts for 5% of the extra energy a Mode 3 uses per mile. To me that is actually surprising - I expected both vehicles to have very similar efficiency chargers.

It also matters for the world to some extent, if your car derives its energy from fossil fuels. Though I frankly think we are screwed at this point, so it probably does not matter all that much.

The last time I checked in my car over a week this winter it was about 20 watts

This is 480Wh/day - 7 times what was claimed above. It is within reason though I suspect you have optimized your setup somehow as it is lower than Tesla expects.

Do you have all the data sharing and stuff turned off? I’m still trying to get to this level (or lower). One of these days I’ll disable the Stats app - however, I also was carefully watching the drain before I installed and it did not appear to change my results - so I suspect it is some other factor.

 

[Daniel in SD]

Not quite. What I care about are both range and driving efficiency. I don't really care if I waste 11% of energy from the wall vs 7%. I care about how well the car will translate available energy from a full pack in to miles driven.

This is in the same way that I don't really care if one gas pump has a couple percentage points of error as compared to another... as long as the pump head clicks off, I know my tank is full, and at that point it's the efficiency of my engine that determines the range I'll have on the road.

Why would you care what the “driving efficiency” if you still get the same range? Just like with the gas pump what you care about is how far you can go on a full tank/battery. The kWh gauge will tell you relative efficiency of different driving conditions but it won’t tell you how far you can go and it’s not comparable to other cars.

 

[scaesare]

Fair enough - but there are people who will make decisions about very efficient gasoline cars based on a 5-10% difference in efficiency

I'm sure, there will be.

Interestingly, I bet none of them compare the fuel lost to evaporative vapor (i.e. compare the effectiveness of gas caps and evap cannisters between manufacturers) nor strive to determine the accuracy of the gas pupms they frequent (which have been shown to vary widely).

The figure of merit for most folks is the mileage the car gets on the road.

Certainly I'm a fan of efficiency... I'll take a 97% efficient charger over one that's at 92% every time, all else being equal.

That having been said: at the $0.11/Kwh I pay for power, a 5% difference in charger efficiency costs me in the neighborhood of 44 cents for a full charge on my S85.

If I'm filling up my 20gal ICE tank with $3/gal gas even a 1% pump error or evap/spillage loss is more than that, at 60 cents. Many gas pumps have been shown to have significantly more error than that. So I;m not gonna sweat that...

 

[Daniel in SD]

The last time I checked in my car over a week this winter it was about 20 watts

Was this measured at the wall? Your car sounds like a unicorn.

 

[scaesare]

Why would you care what the “driving efficiency” if you still get the same range? Just like with the gas pump what you care about is how far you can go on a full tank/battery.

Because, for a given pack capacity (a relatively static value that I had to pay for), the more efficient the driving efficiency the more range I'll get. The two are linked.

The kWh gauge will tell you relative efficiency of different driving conditions but it won’t tell you how far you can go and it’s not comparable to other cars.

I can tell by power usage how accurate the range estimation is. For me if I'm at 275Wh/mi, I know I'll get rated range. If I'm burning more that that (due to heating, wind, elevation, etc...) than I can pro-rate accordingly.

While it may not be directly comparable to other cars, it does provide some basis for comparison. I suspect you would be safe saying a car whose power usage meter indicates 250Wh/mi, is more efficient than one that claims 375....

 

[AlanSubie4Life]

Interestingly, I bet none of them compare the fuel lost to evaporative vapor (i.e. compare the effectiveness of gas caps and evap cannisters between manufacturers) nor strive to determine the accuracy of the gas pupms they frequent (which have been shown to vary widely).

Neither of these factors are comparable to the 5% level. Evaporation is a non issue for discussions of factors of this order of magnitude. Gas pump errors will likely average out to zero error (they are calibrated and put under seal). And I would notice both factors with my ICE vehicle. A single gas pump that is miscalibrated matters a lot less than a 5% hit every time you fuel.

Point taken that it is 5% of a smaller number (not in the case of a Prius though), but I believe both effects mentioned are pretty minuscule.