Usable kw

[gilscales]

I put some new wider larger tires on and I knew it would hurt my efficiency with the Continental Extereme Contact DWS06 in a 255/40/19

For comparison I would get around 270/275 wh/mi same trip with stock 19” rubber and these got 301 wh/mi

I was wondering why I am only showing 69 kWh used going from 100% to 1 mile left on the range meter, we stopped for lunch for about an hour and another 5 min stop but those stops should not have gone through much juice.

Not complaining, love the car, just curious is all.

 

[gilscales]

Teslafi shows 68.41 kWh going from 100% to 1 mile, is this the expected amount of usable battery?

 

[diamond.g]

If you believe Jack Richards, the car "reports" different than what the canbus says. So that brings into question where the API data is coming from, if from canbus then it is reading lower (Jacks car canbus reported 77kWh for pack capacity).

 

[AlanSubie4Life]

I put some new wider larger tires on and I knew it would hurt my efficiency with the Continental Extreme Contact DWS06 in a 255/40/19

For comparison I would get around 270/275 wh/mi same trip with stock 19” rubber and these got 301 wh/mi

I was wondering why I am only showing 69 kWh used going from 100% to 1 mile left on the range meter, we stopped for lunch for about an hour and another 5 min stop but those stops should not have gone through much juice.

Not complaining, love the car, just curious is all.

Tire impact seems about right. Might come down ever so slightly over time.

That's a surprisingly large discrepancy in the trip meter. I've seen a few % low on that in car meter, but nowhere near ~9% low. This is assuming there are 75kWh available of course. "100%" is hard to say - I assume your battery holds 310 rated miles at 100%, but if it doesn't that could be a contributing factor. A battery that full charges to 303 miles contains closer to 73kWh, for example.

Based on your description I assume you didn't do any sitting in the car with the heat or AC on for that 1 hour stop. So the energy loss their should have been pretty low.

I wonder about how they measure Wh used. I have no idea how they do it, whether it's actually measured somehow, or dead reckoned from state of charge estimate, accelerator pedal position, accessory use, etc. Anyway, relevant because if they make some assumptions about energy used to turn the wheels, maybe the tire change is throwing it off. It might decide it should take a certain energy to roll the tires but now that it is taking more it might be underestimating energy use? This hypothesis doesn't really make any sense, I have to say. Again, I have no idea how they measure the Wh consumed. If it's directly measured somehow I have no idea why it would be incorrect.

When I've extrapolated an 80% discharge on my car, it worked out to be something like 73-74kWh. However, due to significant non-linearities at the beginning and end of discharge, I don't know that I can say what it would be if I did a 100% to 0% discharge. It might deviate from the 74kWh number.

 

[gilscales]

Tire impact seems about right. Might come down ever so slightly over time.

That's a surprisingly large discrepancy in the trip meter. I've seen a few % low on that in car meter, but nowhere near ~9% low. This is assuming there are 75kWh available of course. "100%" is hard to say - I assume your battery holds 310 rated miles at 100%, but if it doesn't that could be a contributing factor. A battery that full charges to 303 miles contains closer to 73kWh, for example.

Based on your description I assume you didn't do any sitting in the car with the heat or AC on for that 1 hour stop. So the energy loss their should have been pretty low.

I wonder about how they measure Wh used. I have no idea how they do it, whether it's actually measured somehow, or dead reckoned from state of charge estimate, accelerator pedal position, accessory use, etc. Anyway, relevant because if they make some assumptions about energy used to turn the wheels, maybe the tire change is throwing it off. It might decide it should take a certain energy to roll the tires but now that it is taking more it might be underestimating energy use? This hypothesis doesn't really make any sense, I have to say. Again, I have no idea how they measure the Wh consumed. If it's directly measured somehow I have no idea why it would be incorrect.

When I've extrapolated an 80% discharge on my car, it worked out to be something like 73-74kWh. However, due to significant non-linearities at the beginning and end of discharge, I don't know that I can say what it would be if I did a 100% to 0% discharge. It might deviate from the 74kWh number.

Yes I do still get 310 fully charged but lately I have noticed the first 10 miles or so goes pretty fast, maybe in 3 miles of driving

Car still has plenty of range even with the tire change I was just curious if this is normal, still my favorite car by a wide margin!

 

[gabl]

The reported using in the odometer / trip meter is erroneous.

I suspect it's excluding two points of usage 1) vampire drain (the energy used to maintain the battery and to monitor the sensors when the car is off), and 2) Climate + Music usage while sitting still (I often sit in the school pickup line).

Here's how I tested.

From odometer 1003 miles, 23% SOC (72 rated miles), I charged up to 89% SOC (275 rated miles). The tesla screen reported adding 50 kWh of charge.

I then drove the car down to 23% SOC (72 rated miles) without charging. This took 161.3 miles (odometer 1164). The tesla trip meter said I used 41 kWh.

So, to charge from 72 rated miles (23% SOC) up to 275 rated miles (89% SOC) took 50 kWh. However, to drive from 275 rated miles down to 72 rated miles only used 41 kWh. Where did the other 9 kWh go?

I belive it went to vampire drain and to climate / audio while sitting still.

Test 1. Charge your car. Drive 1 mile. Record the Wh/mi usage "since last charge," and the charge state in rated miles. While sitting in your parked car, use the heater and the radio until the charge state drops by 2 miles. Next check the Wh/mi "since last charge" usage. It will be the same. Each rated mile of charge is about 241 Wh. If the charge stated goes down by 2 rated miles, the Wh/mile should go up by about +500. But it does not. It is the same. The tesla usage reported neglects climate / radio usage while sitting still. (you may ask why I suggest making the charge state drop by 2 rated miles. That reduces rounding error in the measurement.)

Test 2: Charge your car. Drive 1 mile. Record the Wh/mi usage "since last charge," and the charge state in rated miles. Let the car sit for a day or two without driving. After a couple days, notice the charge state in rated miles has dropped by a couple miles. Next check the Wh/mi "since last charge" usage. It will be the same. By the same reasoning as above, you can see the tesla reported usage neglects vampire drain.

I have found that when my car reports usage of 254 Wh/mile, it actually takes about 400 Wh/mile from my outlet. IE, the car uses 56% more energy than it reports. This includes charging inefficiency.

 

[AlanSubie4Life]

I suspect it's excluding two points of usage 1) vampire drain (the energy used to maintain the battery and to monitor the sensors when the car is off), and 2) Climate + Music usage while sitting still (I often sit in the school pickup line).

This is definitely true in general, but based on the OP’s description he did this discharge all in one shot, so the assumption made here is that there is not vampire or parked losses.

Your 254Wh/mi scaling to 400Wh/mi is sadly not out of line either. Seems about right, though it may improve a little bit in warmer weather due to less heat use when parked.

 

[gabl]

This is definitely true in general, but based on the OP’s description he did this discharge all in one shot, so the assumption made here is that there is not vampire or parked losses.

Your 254Wh/mi scaling to 400Wh/mi is sadly not out of line either. Seems about right, though it may improve a little bit in warmer weather due to less heat use when parked.

Maybe Tesla is excluding climate / audio usage from the reported usage even while driving.

I think they should report usage based, at minimum, on all energy flowing from the battery, regardless if it was used for heat or while parked. The model 3 is incredibly efficient, why give erroneous numbers? My ICE cars report properly.

 

[AlanSubie4Life]

Maybe Tesla is excluding climate / audio usage from the reported usage even while driving.

I think they should report usage based, at minimum, on all energy flowing from the battery, regardless if it was used for heat or while parked. The model 3 is incredibly efficient, why give erroneous numbers? My ICE cars report properly.

They most definitely include climate use. Just not while parked. Audio I don’t know, but doesn’t really matter much.

Regarding the reporting...shrug. Tesla makes odd decisions. They are used to a clientele that does not care much about efficiency, I can tell you that.

The numbers aren’t too erroneous, some things just aren’t included. .

 

[gabl]

They most definitely include climate use. Just not while parked.

How do you know / How can this be tested?

 

[AlanSubie4Life]

How do you know / How can this be tested?

Not hard. Just turn on the heat to max (max is open loop I think) and do a test drive of a mile. Then repeat the experiment without the heat on (press and hold to turn off).

 

[gabl]

Not hard. Just turn on the heat to max (max is open loop I think) and do a test drive of a mile. Then repeat the experiment without the heat on (press and hold to turn off).

Will do.