Mike's monthly Model 3 efficiency report

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Mike

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#41
@Mike - love these posts for their data. But the data is pretty damn concerning.

422 kW-hours actual vs car saying 319 kW-hours. That is a huge difference. As you said, better than in November but still a big difference.
Cheers.

I hear you @Nom about the difference.

The first thing I would like to see is a user option for the trip odometers.

Currently, the trip odometers only track energy used while the vehicle is actually moving.

I would like to have the option of having energy use tracked while "in gear".

The second thing that is becoming apparent to me is the "overhead" energy use that "disappears" has a bigger effect than my driving technique (for winter driving, anyway).

My actual "while under way" efficiency per km in summer (about 145 wh per km) is only degraded by 18% (to 171 wh per km) in winter (so far), yet the "overhead" has more than doubled (summer, about 17%; winter, about 38-40%).

As for the heater (18c, manual, fan speed 1, fresh air only) use, sure the first km may have 400 wh used, but then after another 2km the average will already be below 200 and about 2 km after that my typical trip average will settle around 171.

I'm starting to wonder what the battery conditioning portion actually adds up to......
 

Mesprit87

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#42
I agree with you, battery conditioning doesn't even assure the full regen from a 14C garage.
I don't drive the car that much now for different reasons, I wish I had a deep sleep mode for when the car is parked for 4 days even if it means not having the full benefits the car can offer when I'm ready to drive unless I wake it an hour before doing so.
I also agree that this energy won't come back, it's lost or partially if you drive the car daily and it should show somewhere.

Thanks for highlighting this behavior in a well managed environment and parameters.
Now I just need a little more practice driving at 170Wh:eek:
 

Mike

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#43
I wish I had a deep sleep mode for when the car is parked for 4 days even if it means not having the full benefits the car can offer when I'm ready to drive unless I wake it an hour before doing so.
I mused about this early last year, from the perspective of parking at an airport for a week or two.

I proposed an "airport sleep mode" with the expected return time as an entered parameter.
 

Nom

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#44
@Mike - what do you mean by overhead? Is this the energy spent while not in gear? Or is the the energy used by ancillary power drains such as heating, defrost, seat heaters, A/C? Or both?
 

Mike

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#45
@Mike - what do you mean by overhead? Is this the energy spent while not in gear? Or is the the energy used by ancillary power drains such as heating, defrost, seat heaters, A/C? Or both?
@Nom - Since the cars odometer only captures energy use and rate of use while actually moving, "overhead" is any energy used while the car is not moving.

This can include, but not be limited to:
  • All energy used while sitting in the car and the car is not in motion, such as at a stop light or sitting in a garage while in drive or reverse;
  • All energy that is used to keep the car awake and ready to accept inputs from the key system that is being used;
  • All energy that is drained away as "vampire" drain;
  • All energy that is lost in the AC/DC conversion process while charging from the AC grid; and
  • All energy used for battery conditioning.

Once could say it is energy not used in propulsion, but while underway (and the odometer is keeping count) one will have secondary systems draining away energy such as HVAC, lights, seat and/or window heaters, the infotainment system, the steering and braking system, etc.
 

Mike

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#46
My numbers for January 2019:

Car odometer:
  • kWhs uploaded: 211, and
  • Wh/km: 185.
img_0151-jpg.21337


Actual:
  • kWhs uploaded: 309, and
  • Wh/km: 272.

kwhs_inputs_jan2019-png.21339


real_wh_per_km_31jan2019-png.21338


For January 2019, a 47% overhead between the odometer and real upload.

It's higher than the 43% I was expecting this month because I kept the HVAC on almost every time I went to the YMCA due to the sub -15c temperatures.

Only one away trip of 550 (+/-) kms total, the rest of the trips are very short and in town.

----------------------------------------------------

Sidebar: cost to operate per km (all figure $CAN).

Now that I have eight months under my belt with the car, some operating cost numbers are starting to solidify:

summary_31jan2019-png.21340


Not including purchase (and depreciation within that amount), I am running at $0.1956 per km.

Cost per km for "fuel" is just over 3 cents per km ($0.0311) and is being driven up because of the (relatively) inefficient use of it in winter conditions.

I suspect a year from now, once finance costs are winding down, the running costs will be somewhere near 15 cents per km.
 
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#47
Wanted to say that this is such a super useful thread. I am using teslafi to extract this data as well, alebeit manually.
In the winter my cost is ~10c/kWh while charging at night.
I use about ~ 73kWh to top off the battery from 10% up at 92.5% efficiency at home.
So, topping off costs me about $7.30 USD and in the winter I get about 200-220 miles for that. With HVAC running, winter tires with limited regen, etc., etc.

I am seeing something similar to your costs in energy costs as well: 3.3-3.65 cents / mile
 

Mesprit87

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#48
I was expecting a higher Wh/km increase with the temperatures we've got in January.
I think the higher 47% delta can be partly explained by the warming up of the battery when plugged in on your return? I know that when I get back from work, 40Km, the battery is still pretty cold when I plug it in (if I plug it in). I'm still wondering if it's more economical to let warm up slowly in the garage before plugging the charger.
 

Mike

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#49
Wanted to say that this is such a super useful thread. I am using teslafi to extract this data as well, alebeit manually.
In the winter my cost is ~10c/kWh while charging at night.
I use about ~ 73kWh to top off the battery from 10% up at 92.5% efficiency at home.
So, topping off costs me about $7.30 USD and in the winter I get about 200-220 miles for that. With HVAC running, winter tires with limited regen, etc., etc.

I am seeing something similar to your costs in energy costs as well: 3.3-3.65 cents / mile
Cheers.

Glad you can get some useful information from this.

I'm a data nerd, so there you go.

All kidding aside, I use this hard data to discuss real world energy use with other family members, friends and neighbors.

When an honest question comes up in those discussions, I can spit out the numbers I get without embellishments.

I do wish I had the option to have my trip odometers capture energy use anytime the car is "on" and apply it to the figures we see.
 

Mike

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#50
I was expecting a higher Wh/km increase with the temperatures we've got in January.
I think the higher 47% delta can be partly explained by the warming up of the battery when plugged in on your return? I know that when I get back from work, 40Km, the battery is still pretty cold when I plug it in (if I plug it in). I'm still wondering if it's more economical to let warm up slowly in the garage before plugging the charger.
It's very rare that I begin a charge session after just pulling into the garage.

In practice, the car will have about 18 hours to acclimatize to my garage environment prior to charging up.
 

Mesprit87

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#51
It's very rare that I begin a charge session after just pulling into the garage.
If I undertand you well, you don`t connect it as you get in. Because you could connect and not charge.

by the way, I use your realistic 0.03$ when people ask me (and lot do at work!) what the "fuel" cost is. I think it's the easiest metric to use when talking to people.
 

Mike

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#52
If I undertand you well, you don`t connect it as you get in. Because you could connect and not charge.

by the way, I use your realistic 0.03$ when people ask me (and lot do at work!) what the "fuel" cost is. I think it's the easiest metric to use when talking to people.
You are correct, I don't connect when I pull back into the garage unless I am planning a recharge session within the next 24 hours.

I have, from time to time, had the car immediately draw power from the wall connector as soon as I pulled and and connected it.......with the HVAC turned "off".

I'm not sure if that is battery conditioning or just my car being finicky.

When that does happen, I unplug the car and then wait about 30 minutes and then re plug it in with no power draw.

Three cents a km for fuel is what I tell folks as well, with the caveat that it is four cents in the winter and two cents in the summer.
 

Mike

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#53
If I undertand you well, you don`t connect it as you get in. Because you could connect and not charge.

by the way, I use your realistic 0.03$ when people ask me (and lot do at work!) what the "fuel" cost is. I think it's the easiest metric to use when talking to people.
Sidebar: one other metric has come out in discussions with "sceptics".

In replying to an assumption that I had to search for a charger when we went to Ottawa last weekend with, "We arrived at the inlaws and I plugged into their outlet by the front door", the follow-up question was, "Well what happens if the highway is closed due to a weather related accident and you are stuck on it? You are going to run out."

Based on the rates of energy usage I saw while keeping my HVAC running while I was at the YMCA for most of last month, I can reply "3% an hour".

With temperatures at or around -20c, with the HVAC set to 18c and fan speed "1" with fresh air only, my energy spend was always 3% for an hour while at the YMCA.
 

Trevlan

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#54
For me another way to explain to others is I use 1kw for every 6km but in winter I have been more like 1kw to 3.5-4km a lot less.
On the minus 20 days I was almost 1-1 drove 1km and used 2 but I still have more than enough to get me by. Yes if I get stuck on a highway I will use the how many clicks to a SC and if I have double I am ok!
 

PNWmisty

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#55
You are correct, I don't connect when I pull back into the garage unless I am planning a recharge session within the next 24 hours.

I have, from time to time, had the car immediately draw power from the wall connector as soon as I pulled and and connected it.......with the HVAC turned "off".

I'm not sure if that is battery conditioning or just my car being finicky.

When that does happen, I unplug the car and then wait about 30 minutes and then re plug it in with no power draw.
The immediate power draw upon plugging in when not recharging the traction battery was probably the recharging of the 12V battery. I'm guessing it's considerably more efficient to charge the 12V battery when plugged in vs. charging it from the traction battery and then having to re-charge the traction battery, you may be better off plugging in as soon as you arrive home (not to mention less cycling of the traction battery). At least that's what Tesla recommends. Ironically, your overall electrical consumption numbers may very well be lower if you plugged in all the time rather than relying on the traction battery to power things when at home.
 

ADK46

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#56
This thread is a nerd's delight! Some very interesting details about the energy usage display. I probably missed other details in this thread, but wonder if my understanding of overall grid to wheels efficiency is incorrect:

Considering the path into the battery and then out the wheels, there are

1) I^2R losses in the conductors along the way - not much, usually, but proper nerds will recognize the evil of a squared term.​
2) AC to DC conversion loss in the charger - my impression is that this runs about 5-15% - 5% would be an optimistic assumption.​
3) The round trip efficiency within the battery is less than 100% - I've never encountered a number for this, probably depends on all sorts of things - at least 5% loss is my guess. Perhaps it's as simple as I^2R where R is the battery's internal resistance. Anyway, a battery being charged gets hot!​
4) Inverter loss - like the charger, these are quoted as something like 5 - 15%, depending on current (better at high rates, though certainly not enough to compensate for aero effects).​
5) Motor loss(es) - a few percent at least - 5%?​
6) Gearbox losses - a few percent, maybe. Double for dual-motor​

Add them all up and weep. This would be for the simple grid-to-wheels losses, not counting any other energy drawn from the traction battery.

=========

I'm holding back on a full rant about terminology, but I cannot contain myself about this one: instead of "fuel", just say energy. No quotes required. Eschew archaic terms! We're not shoveling coal into boilers any more. (Someone tell West Virginia.)

Oh dear, another: Units named after people are not capitalized when spelled out (watts, kilowatts, teslas), but they are capitalized when used as symbols (W, kW, T). No need to make them plural - "My car used 23 kWh of energy", not kWhs.

Someone bring me more coffee!
 

Mike

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#57
The immediate power draw upon plugging in when not recharging the traction battery was probably the recharging of the 12V battery.
On those rare occasions where I saw this strage behavior, the draw that I saw on my in line meter suggests some other reason.

IIRC, it was about 2.4 kW of draw.

EDIT: On one of the other threads (here or TMC, can't remember which one) where they are drilling down to view the actual pattern for the float charge schedule being used by the Model 3, it seems whenever the car is "on", the DC/DC converter is supplying a float charge above 14 volts.

Once the 12 volt battery is on its own, it's only being allowed to discharge to something like 12.9 volts (?, not sure of exact numbers) to prevent the "deep discharge" issues seen on Model S and X before the clunk is heard and the DC/Dc converter goes live to re-top up the 12 volt battery.

When I do come home and plug in right away, with HVAC off, there is (usually) never any draw from the grid.

EDIT 2 corrections: 12 volt float charge when car is on: 14.8 volts. Lowest voltage on 12 volt battery before 12 volt battery is charged: 13.3 volts.
 
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Mike

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#58
I'm holding back on a full rant about terminology, but I cannot contain myself about this one: instead of "fuel", just say energy. No quotes required. Eschew archaic terms! We're not shoveling coal into boilers any more. (Someone tell West Virginia.)

Oh dear, another: Units named after people are not capitalized when spelled out (watts, kilowatts, teslas), but they are capitalized when used as symbols (W, kW, T). No need to make them plural - "My car used 23 kWh of energy", not kWhs.
Consider me debriefed. :)
 

Mike

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#59
The immediate power draw upon plugging in when not recharging the traction battery was probably the recharging of the 12V battery. I'm guessing it's considerably more efficient to charge the 12V battery when plugged in vs. charging it from the traction battery and then having to re-charge the traction battery, you may be better off plugging in as soon as you arrive home (not to mention less cycling of the traction battery). At least that's what Tesla recommends. Ironically, your overall electrical consumption numbers may very well be lower if you plugged in all the time rather than relying on the traction battery to power things when at home.
Here is the link to the 12 volt battery charge information:

https://teslaownersonline.com/threa...12v-battery-for-the-model-3.10772/post-195856
 

PNWmisty

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#60
EDIT: On one of the other threads (here or TMC, can't remember which one) where they are drilling down to view the actual pattern for the float charge schedule being used by the Model 3, it seems whenever the car is "on", the DC/DC converter is supplying a float charge above 14 volts.

EDIT 2 corrections: 12 volt float charge when car is on: 14.8 volts. Lowest voltage on 12 volt battery before 12 volt battery is charged: 13.3 volts.
I have an Escort 8500 set to display system voltage (from 12V outlet in center console) whenever the car is being driven. My observation has been that it displays 15.3V (about 0.5V higher than other cars I've used it in) when charging and occasionally drops down around 13.4V while driving. It seems like it's at the higher value more than half the time. The 15V value is very steady at 15.3V but the 13V value varies. I've never checked the accuracy of the voltmeter built into the 8500 but I bet it's within 0.15V or so.

When I do come home and plug in right away, with HVAC off, there is (usually) never any draw from the grid.
That's how mine is (assuming the flashing/moving LED's on the EVSE are any indication). But sometimes there is (current draw) and, when there is not, you can bet there will be in anywhere from a few minutes to a few hours. So I'm clueless why you decide not to plug it in when you arrive. This could lower your consumption and reduce cycling of the traction battery.