Energy accounting

[ElSupreme]

I ended up losing ~5 miles to the vampire at work. On the drive home I finished up with 266 Wh/mi and made back all the vampire losses. So total trip of 56 miles. Started at 224 miles. Ended with 168 miles at home. So I "banked" 5 miles on the way home using the same energy rate.

As soon as I start working less than 7 days or 60 hours in a week I'll setup the REST API tools.

 

[scaesare]

I've noticed higher-than-normal energy usage for the last 2 weeks or so. Even though the temperature has dropped only gradually, I suspect that it's crossed the threshold where the car needs to use the electric pack heaters for at least an initial portion of the trip. Temps for me have gotten in to the 40's in the evenings.

For me, the amount of energy is rather slight thus far: energy averages in the mid-300's of Wh/mi, whereas for the previous 4.5 months it had been right around 300. I've specifically not used the cabin heater on several occasions just to see if that was the primary culprit. Even with it off, the energy is increased, so I suspect it's the pack heater.

As an interesting aside, the additional energy usage appears to to be reflected in the "Since last charge" counter on the dash trip meter, but not in my rolling average on the Energy center or dash screens...

 

[Cottonwood]

As an interesting aside, the additional energy usage appears to to be reflected in the "Since last charge" counter on the dash trip meter, but not in my rolling average on the Energy center or dash screens...

That is exactly how averages work!

Let's take an example in another space. Say you have spent $100/week for groceries for the last year (52 weeks), and in the last week, you started reading Bon Appetit and the grocery bill went to $200 in the last week. Up until this week, your annual average grocery expenditures and the last week's expenditure would both be $100/week, but after the Bon Appetit week, the average annual would be $102/week, but the average since last purchase would be $200/week. It takes time to swamp out all of those thrifty weeks with the new high expenditure weeks in the long term average.

 

[scaesare]

That is exactly how averages work!

Yes, I understand what an average is.

My point being: after ~30 miles (i.e. just about the distance of one leg of my trip) my Odometer average will now be ~350 Wh/mi. My center screen 30 mile average will read 308Wh/mi.

Prior to the colder weather, the two would match pretty closely.

 

[tomas]

I've noticed higher-than-normal energy usage for the last 2 weeks or so. Even though the temperature has dropped only gradually, I suspect that it's crossed the threshold where the car needs to use the electric pack heaters for at least an initial portion of the trip. Temps for me have gotten in to the 40's in the evenings.

For me, the amount of energy is rather slight thus far: energy averages in the mid-300's of Wh/mi, whereas for the previous 4.5 months it had been right around 300. I've specifically not used the cabin heater on several occasions just to see if that was the primary culprit. Even with it off, the energy is increased, so I suspect it's the pack heater.

As an interesting aside, the additional energy usage appears to to be reflected in the "Since last charge" counter on the dash trip meter, but not in my rolling average on the Energy center or dash screens...

Yep, that's exactly how it happens. Temps get below 50, and average range goes down. Also correct that "since last charge" and "rolling average" are not always in synch, tho I seldom experience as large a disparity as you note. None of this a problem, just a fact to know as we triangulate range and efficiency. I got my car 12/18/12, and am patiently awaiting a 12 month wh/mi average to see what 4 season looks like here in Chicago. I got down to 325 avg over 10,300 miles during early October, but I'm now headed in the "wrong" direction. Guessing I'll finish 4 seasons at about 330. Not bad, about 5% off EPA, which is better than I've ever done with a gas powered car.

 

[Cottonwood]

Yes, I understand what an average is.

My point being: after ~30 miles (i.e. just about the distance of one leg of my trip) my Odometer average will now be ~350 Wh/mi. My center screen 30 mile average will read 308Wh/mi.

Prior to the colder weather, the two would match pretty closely.

Sorry for my misunderstanding of what you were referring to.

Very interesting... I will have to look at that. Perhaps the trip counters are including the environmental loads of the cabin and battery heater with the motive energy use, but the plot and average on the energy page only include motive energy uses.

 

[scaesare]

Sorry for my misunderstanding of what you were referring to.

Very interesting... I will have to look at that. Perhaps the trip counters are including the environmental loads of the cabin and battery heater with the motive energy use, but the plot and average on the energy page only include motive energy uses.

No problem...

The scenario you describe is one we were surmising about at the beginning of this thread...

 

[scaesare]

Above 50 degrees this morning. My commute energy usage is right back to it's normal ~300Wh/mi rate.

Also right at 30 mile mark, my odometer energy average, and the center console 30mi average were only 4wh's apart...

It does appear that 50 degrees is the magic number...

 

[WarpedOne]

Sorry, to revive an oldish thread ... do you guys run with regen on standard or low? Have you tried to change the setting to see if there is any effect on accuracy?

I'd guess that the car does very well counting the VAses going out of the battery but it has a hard time counting the VAses that went into the battery and stayed there (i.e. were not 'consumed' for heating the battery). Charging efficacy varies with temperatute, SOC, current, voltage difference between battery voltage and induced voltate, battery "quality"/age etc. I see differences on the scale of 5%. I could believe it is indeed due to regen puting back some energy the car has problem accounting for.

On the other hand this would mean the range would decrease more slowly than expected not faster ... except if car thinks charging with regen is more efficient than it really is.

 

[scaesare]

I leave it on standard... on significant downhill grades I actually see the energy consumed decrease on the trip meter as a result of regen.

 

[Cottonwood]

I leave it on standard... on significant downhill grades I actually see the energy consumed decrease on the trip meter as a result of regen.

Always leave regen in in standard! Its like driving a sports car in a low gear; get used to it and you will regen more energy. Why use your stored kinetic and potential energy to heat up the brakes?

BTW, regen a full 1.0 kW-hr and the rated miles in the battery will show an increase of 3-4 miles. Until you get that 1 kW-hr, nothing is shown in the rated miles in the battery but the trip display will show 0.1 kW-hr level recovery in energy used. If you regen 0.3 or 0.6 kW-hr, those 1 or 2 rated miles are phantom in the display, but the rated mile counter won't start counting down again until you use up that real energy in the battery.

 

[bluetinc]

I've found that my accounting is accurate to within ~100Wh/80,000Wh or ~0.1%. If you are off by ~5% then you are probably not accounting for the percentage of energy that they siphon off while driving to provide a buffer below 0.

Peter

Sorry, to revive an oldish thread ... do you guys run with regen on standard or low? Have you tried to change the setting to see if there is any effect on accuracy?

I'd guess that the car does very well counting the VAses going out of the battery but it has a hard time counting the VAses that went into the battery and stayed there (i.e. were not 'consumed' for heating the battery). Charging efficacy varies with temperatute, SOC, current, voltage difference between battery voltage and induced voltate, battery "quality"/age etc. I see differences on the scale of 5%. I could believe it is indeed due to regen puting back some energy the car has problem accounting for.

On the other hand this would mean the range would decrease more slowly than expected not faster ... except if car thinks charging with regen is more efficient than it really is.