Do you trust the efficiency number in the trips display?

[GrantK]

Hi,

I think the efficiency number in the trips display is lying

[Edit] Note my question is not about range, it is about the reported efficiency. For range there will always be inaccuracy as you are predicting future events. For efficiency you are measuring past events (miles driven / kWh used).

For example I started with my (standard range) battery at 90% this morning and drove 62.1 miles at 3.5 mi/kWh according to the trip meter. At the end of the trip my battery was at 57%, so I used 33% of my battery.

My battery has about 5% degradation which I measured a few weeks back and 62 * 3 (33%) would give a total range of 186 miles which seems about right for a Select AWD in the relatively mild winter of the SF Bay Area.

So if I assume the claimed efficiency is correct then 62.1 mi / (3.5 mi/kWh) = 17.7 kW and if that is a 3rd of my battery that would make my battery size 53kW (while it should be in the high 60's after a bit of degradation?)

If I work with a battery size of 68kW (I got a couple of kW unlocked by the update, minus the degradation) then my trip this morning would be at about 2.7 mi/kWh which feels much more realistic.

 

[AliRafiee]

It is known as guess-o-meter.
Even on a gas car.

 

[ctenidae]

I find that all of the metrics provided by the car are accurate within certain relatively stable margins of error. Any one metric or set will generate an inaccurate assessment of your current charge/range situation, but several methods taken together will generally be similar enough to give you a good sense of what PuckerFactor you should be applying to your driving.

I find that using a SWAG-based modifier to the BOTEK calculator works well, except if time, temperature, or weight are significant factors. In that case the PuckerReduction variable needs to be adjusted to account for potentially lower readings than expected. I think in-car monitoring of the GoM range remaining (DTE less DTD) as it relates to the SoC-kw/m ratio is useful in maintaining an appropriate PuckerLevel.

 

[Mach-Lee]

Hi,

I think the efficiency number in the trips display is lying

[Edit] Note my question is not about range, it is about the reported efficiency. For range there will always be inaccuracy as you are predicting future events. For efficiency you are measuring past events (miles driven / kWh used).

For example I started with my (standard range) battery at 90% this morning and drove 62.1 miles at 3.5 mi/kWh according to the trip meter. At the end of the trip my battery was at 57%, so I used 33% of my battery.

My battery has about 5% degradation which I measured a few weeks back and 62 * 3 (33%) would give a total range of 186 miles which seems about right for a Select AWD in the relatively mild winter of the SF Bay Area.

So if I assume the claimed efficiency is correct then 62.1 mi / (3.5 mi/kWh) = 17.7 kW and if that is a 3rd of my battery that would make my battery size 53kW (while it should be in the high 60's after a bit of degradation?)

If I work with a battery size of 68kW (I got a couple of kW unlocked by the update, minus the degradation) then my trip this morning would be at about 2.7 mi/kWh which feels much more realistic.

Yes, it's usually accurate as long as you didn't use departure time or remote start first.

70 kWh x 95% health x 93% capacity @ 10ºC = 62 kWh - 3 kWh buffer = ~ 59 kWh usable 100-0%.

62.1 mi ÷ 3.5 mi/kWh = 18 kWh used or 18/59 = 31% used. So pretty close to the 33% observed. 2% difference could be due to pack temp changes since charging finished. The 90% displayed is not a true 90% unless it just finished charging, it was probably like 88% when you left (display might correct quickly in the first mile of driving).

So the two factors you missed was reduced battery capacity due to temperature and the remaining buffer below 0% that Ford counts as usable kWh.

 

[Kevstone]

How on earth did you get those figures in "How's my driving". My deceleration figure drops like a stone at the first junction I get to (1pd).

 

[Blue highway]

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Yes, it's usually accurate as long as you didn't use departure time or remote start first.

70 kWh x 95% health x 93% capacity @ 10ºC = 62 kWh - 3 kWh buffer = ~ 59 kWh usable 100-0%.

62.1 mi ÷ 3.5 mi/kWh = 18 kWh used or 18/59 = 31% used. So pretty close to the 33% observed. 2% difference could be due to pack temp changes since charging finished. The 90% displayed is not a true 90% unless it just finished charging, it was probably like 88% when you left (display might correct quickly in the first mile of driving).

So the two factors you missed was reduced battery capacity due to temperature and the remaining buffer below 0% that Ford counts as usable kWh.

One additional factor that might explain the 2% is that the reported SOC is not linear compared to what you see from the OBD port. The reported SOC is "S" shaped. 1% SOC change near 50% = 1% SOC change displayed. Near the top and bottom of the pack, the Displayed SOC changes more than the OBD SOC.

There was a post in the forum where someone took the time to graph this out... can't find it at the minute.

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