Perplexed about my efficiency

[victoryroad]

I cannot figure out why I can get 4.2 miles/kWh on the same 40 mile trip in 90 degree weather today and only about 3.2 to 3.6 on other days with the same ambient conditions. I am obviously mindful of my average speed and acceleration rates, which are basically identical for every drive on that route. (The LEO's are obsessive about the limits in VA.) Half of the route is on an interstate at about 70-75 and the other on a secondary road with a few traffic lights and average speed of 55. Yes, sometimes I get two green lights and sometimes only one of the three lights that are on the route. Little change in elevation. Same starting SOC of ~80% and no passengers or luggage. My overall efficiency is 3.6.

 

[hydbob]

I cannot figure out why I can get 4.2 miles/kWh on the same 40 mile trip in 90 degree weather today and only about 3.2 to 3.6 on other days with the same ambient conditions. I am obviously mindful of my average speed and acceleration rates, which are basically identical for every drive on that route. (The LEO's are obsessive about the limits in VA.) Half of the route is on an interstate at about 70-75 and the other on a secondary road with a few traffic lights and average speed of 55. Yes, sometimes I get two green lights and sometimes only one of the three lights that are on the route. Little change in elevation. Same starting SOC of ~80% and no passengers or luggage. My overall efficiency is 3.6.

My first suspicion is a headwind

 

[Neurio]

My first suspicion is a headwind

More likely a tailwind today

 

[victoryroad]

Little to no wind. Half S to N and half E to W.

 

[Bobby]

I cannot figure out why I can get 4.2 miles/kWh on the same 40 mile trip in 90 degree weather today and only about 3.2 to 3.6 on other days with the same ambient conditions. I am obviously mindful of my average speed and acceleration rates, which are basically identical for every drive on that route. (The LEO's are obsessive about the limits in VA.) Half of the route is on an interstate at about 70-75 and the other on a secondary road with a few traffic lights and average speed of 55. Yes, sometimes I get two green lights and sometimes only one of the three lights that are on the route. Little change in elevation. Same starting SOC of ~80% and no passengers or luggage. My overall efficiency is 3.6.

Average is more important. Sample size is too small at 40 miles.

 

[Pragmatic]

I've noticed with mine, electricity used during charging (hvac, etc.) is charged to the first mile. If I've just charged it will take 50 miles or more to get from 2.0 to my average of 4.0.

 

[Buffalo Bob]

I've noticed with mine, electricity used during charging (hvac, etc.) is charged to the first mile. If I've just charged it will take 50 miles or more to get from 2.0 to my average of 4.0.

I'm not questioning what you are observing on the pilot panel, but I cannot imagine that the cause is what you think it is. Maybe some residual cooling of the battery, which I imagine heats up during charging, or increased A/C use if the car was not being air conditioned during charging, but I have to believe that the bulk of those items rack up against the total kWh delivered as they are delivered.

 

[Adnillien]

I'm not questioning what you are observing on the pilot panel, but I cannot imagine that the cause is what you think it is. Maybe some residual cooling of the battery, which I imagine heats up during charging, or increased A/C use if the car was not being air conditioned during charging, but I have to believe that the bulk of those items rack up against the total kWh delivered as they are delivered.

I think you are correct. The battery and cabin cooling plays a big roll. If I leave my garage at a cool 90 degrees inside the garage and drive in 112 degree weather I can get 3.8 mi/kWhr on a short 30 mile drive. If the car has been sitting outside in those ambient conditions, I will get 2.4 m/kWhr for the same drive.

 

[Pragmatic]

I was basing my observation on the first 50 miles after a fast charge. On a long trips I fairly consistantly get 4.0, going a steady 75 (indicated). After a 30 minutes DCFC where I leave the ac on and charge from 10% to 80%, the trip screen will start out at 1 m/kw-hr. After 20-30 miles of highway driving it will climb to 2.5 m/kw-hr. It's not until I'm past 50-60 miles that it starts approaching 4.0 m/kw-hr.
Short trips have too variables so they are not useful in comparing efficiencies. It would be nice if there was a display of rolling efficiency over the last mile of driving.

 

[Steveinarizona]

Short trips have too variables so they are not useful in comparing efficiencies. It would be nice if there was a display of rolling efficiency over the last mile of driving.

Is there a way to shut off and restart the log? Could you do that just before you wanted to test the last mile?

 

[BS8899]

I think you are correct. The battery and cabin cooling plays a big roll. If I leave my garage at a cool 90 degrees inside the garage and drive in 112 degree weather I can get 3.8 mi/kWhr on a short 30 mile drive. If the car has been sitting outside in those ambient conditions, I will get 2.4 m/kWhr for the same drive.

Yes, with extreme high summer ambient temperatures in places like Phoenix, cooling down the cabin on short trips can be a big factor. If the AC runs at 20,000 BTUs for the cool down phase, it draws 6kW of power. If it takes 20-30min to cool down the cabin, there goes 2-3kWh!

Some EVs (Rivian, Tesla {I was told}) has "real-time" efficiency charting (10min running intervals). I found it very helpful to understand and optimize my driving.

I have a "suspicion" (i.e., unverified hunch) that long-term vampire drain also affects the Lucid's reported efficiency numbers. From time-to-time, I rotate between my AGT and R1S. In so doing, I leave the AGT sitting for weeks (plugged into L2 charging) and when I drive the AGT again, the initial efficiency numbers are lower than expected. I have NOT done a controlled experiment to validate this suspicion but it could be a factor.

 

[Halodde]

Is there a way to shut off and restart the log? Could you do that just before you wanted to test the last mile?

I think the only thing you can do is reset trip A or B. But once you do that, that data is lost. Unless @borski has a way to recapture it from his hacking system lol

 

[illopp00]

Maybe the ambient temperature is really effecting the battery performance? Ie initial and overall pack temperature? I wish Lucid had a service mode to show Pack temp at least. And then we don't know what is going on with conditioning the pack vs the HVAC.

 

[Adnillien]

If the AC runs at 20,000 BTUs for the cool down phase, it draws 6kW of power. If it takes 20-30min to cool down the cabin, there goes 2-3kWh!

We know the medium power inverter which powers the battery and cabin cooling is 10kW so the drain from AC and battery cooling is likely greater than 6kW when it is very hot out.

 

[momo3605]

I have a "suspicion" (i.e., unverified hunch) that long-term vampire drain also affects the Lucid's reported efficiency numbers. From time-to-time, I rotate between my AGT and R1S. In so doing, I leave the AGT sitting for weeks (plugged into L2 charging) and when I drive the AGT again, the initial efficiency numbers are lower than expected. I have NOT done a controlled experiment to validate this suspicion but it could be a factor.

“Since last charged” takes vampire drain into account. If you reset Trip A at the same time as you finish charging. Then monitor it for a few days, you will find the efficiency of “Since Last Charged” to be lower than expected.

So basically use Trip A if you don’t want to see vampire drain effects

 

[DreamTour]

I think you are correct. The battery and cabin cooling plays a big roll. If I leave my garage at a cool 90 degrees inside the garage and drive in 112 degree weather I can get 3.8 mi/kWhr on a short 30 mile drive. If the car has been sitting outside in those ambient conditions, I will get 2.4 m/kWhr for the same drive.

A "Cool" 90 degrees made me chuckle.

All a matter of perspective i guess.

 

[DreamTour]

I cannot figure out why I can get 4.2 miles/kWh on the same 40 mile trip in 90 degree weather today and only about 3.2 to 3.6 on other days with the same ambient conditions. I am obviously mindful of my average speed and acceleration rates, which are basically identical for every drive on that route. (The LEO's are obsessive about the limits in VA.) Half of the route is on an interstate at about 70-75 and the other on a secondary road with a few traffic lights and average speed of 55. Yes, sometimes I get two green lights and sometimes only one of the three lights that are on the route. Little change in elevation. Same starting SOC of ~80% and no passengers or luggage. My overall efficiency is 3.6.

Something that might give you a more accurate read is to measure the last 20 miles of the trip each way after all the conditioning is done. I've done this after a fast charge session to get a better idea of how much impact on the battery the fast charge session is (after unplugging) to condition the battery. I share the observations here, you can burn 2 Kwh easily after a fast charge session with the car working hard to get the battery back down to ideal tempurature in a short period of time. On a 40 mile trip, that's a 20% tax. Starting cabin / battery temps may make a big impact.

 

[openball]

I cannot figure out why I can get 4.2 miles/kWh on the same 40 mile trip in 90 degree weather today and only about 3.2 to 3.6 on other days with the same ambient conditions. I am obviously mindful of my average speed and acceleration rates, which are basically identical for every drive on that route. (The LEO's are obsessive about the limits in VA.) Half of the route is on an interstate at about 70-75 and the other on a secondary road with a few traffic lights and average speed of 55. Yes, sometimes I get two green lights and sometimes only one of the three lights that are on the route. Little change in elevation. Same starting SOC of ~80% and no passengers or luggage. My overall efficiency is 3.6.

I get the best range when I charge to 80% and plug in everyday, keeping the car between 70%-80%
If I charge above 80% my range drops, or if I depend on free chargers and charge only when it drops below 40% my range is also low.
It could be regen peaks at around 80% or the car is just more efficient at that charge level

 

[NNPCdude]

I think 40 miles is a bit too short to get that level of efficiency. I just returned from a 332mile drive and got 4.3m/kwh on the 200mile leg btw recharging. I also found cruise control (73miles/hr is the sweet spot for me) to consistently get me above 4m/kwh.

 

[Buffalo Bob]

I think 40 miles is a bit too short to get that level of efficiency. I just returned from a 332mile drive and got 4.3m/kwh on the 200mile leg btw recharging. I also found cruise control (73miles/hr is the sweet spot for me) to consistently get me above 4m/kwh.

Remember too that 73 MPH on the speedometer is really more like 70-71 MPH.