Major discrepancy between trip meter avg energy and speedometer energy usage

[Atebit]

In my experience, the heater sucks - the battery. I guess, dress warm, wear gloves, bring a blanket. We do.

Don't take this the wrong way, but I think the notion that you need to "bundle up" in the $100K "car of the future" is a little disconcerting. It's tough enough driving 400 miles for 7 plus hours up and down the east coast in a relatively comfortable (that is, warm) car. Doing that drive in mittens and a comforter is much worse.

I made many the "short" trip in the LEAF sans heat to avoid reaching BINGO energy before my destination, and it was no fun. But having to bundle up in the cabin while cruising I-95 for hours will do nothing for the spouse approval factor, I'll tell you what.

 

[stevezzzz]

I agree that driving with the heat off just to make it to your destination is no fun, Atebit. But since the hit on range is predictable as the temperature drops, I suggest to the OP that you just have to plan for it. There are steps you can take to manage the issue. For instance, don't leave home with a cold battery and a cold cabin: charge the battery and run the climate control just before you unplug and go. Twenty to thirty minutes is plenty to get everything up to temp while on shore power (just be sure you're not set to Range Mode while preheating: it limits heating current). As you drive away, turn the heater set point down to 66-67, set the car to Range Mode and then just turn off the Climate system: you'll run a good long while without any excess battery drain, until you feel the need to turn the heater back on again. These steps will help maximize your cold-weather range when you have any doubt about reaching your destination. Slowing down is also your first line of defense when range is an issue, with this important caveat: when the weather is really cold, the speed at which you get max range is higher than it is in warmer weather, because your heating draw remains essentially fixed at any speed and if you slow down too much you'll spend a lot of extra time heating the cabin (and the battery, if it's really cold).

Of course, the easiest thing to do is to plan your charging stops with cold-weather range in mind, so you don't have to worry about driving slow and turning off the heater.

 

[robbie380]

If I'm understanding the OP's question, I don't think anyone has tried to answer it. It seems like he is saying that the kW meter on the *speedometer* is not matching with the trip computer. Whatever extra power is required due to cold, tires, heater, etc., should certainly be reflected in the kW meter on the speedometer, so the kW there should match the trip computer?

That is correct. The kW meter is not matching up with the trip meter. The kW meter would not even be going above 40 and the trip meter would be showing a wh/mile reading of over 400 as I was cruising at 71 mph.

I was reading this bit from the OP's posts over and over, and I don't get it... I don't see how you can correlate the energy gauge on the speedometer to wh/mile? Am I missing something?

Maybe I am doing something wrong. I've only had the car a few weeks now. Let's say the kW meter was at 20 and you were going 60 mph I thought that was supposed to equate to a 200 wh/mile reading on the trip meter. Maybe I am screwing something up. That could be entirely possible.

 

[bluetinc]

Hi Robbie,

I think this should help explain the confusion:

The display meter is showing power (kW). When you are talking about Wh/mi, you are talking about energy per mile, or power*time/mile.

For your example of 20 kW while driving at 60 miles per hour, your Wh/mi would be 20,000W/60mi/h -> 333 Wh/mi.

If you were using 40 kW of power while driving at 71 miles per hour, that's 40,000W/71mi/h -> 563 Wh/mi.

Does this help things make a little more sense?

Peter

That is correct. The kW meter is not matching up with the trip meter. The kW meter would not even be going above 40 and the trip meter would be showing a wh/mile reading of over 400 as I was cruising at 71 mph.



Maybe I am doing something wrong. I've only had the car a few weeks now. Let's say the kW meter was at 20 and you were going 60 mph I thought that was supposed to equate to a 200 wh/mile reading on the trip meter. Maybe I am screwing something up. That could be entirely possible.

 

[flyeyes]

Hi Robbie,

I think this should help explain the confusion:

The display meter is showing power (kW). When you are talking about Wh/mi, you are talking about energy per mile, or power*time/mile.

For your example of 20 kW while driving at 60 miles per hour, your Wh/mi would be 20,000W/60mi/h -> 333 Wh/mi.

If you were using 40 kW of power while driving at 71 miles per hour, that's 40,000W/71mi/h -> 563 Wh/mi.

Does this help things make a little more sense?

Peter

+1

I think the majority of the confusion here is that the magnitude of the numbers is about the same, so people assume they are measuring the same thing.

The dashboard meter is instantaneous kW, which would be analogous to "gallons per hour" which is common in boats or aircraft but not in cars. The big screen number is kWh/mi which is analogous to miles per gallon, which is typical in cars (but pretty rare in aircraft).

Two different measurements.

 

[brianman]

The dashboard meter is instantaneous kW, which would be analogous to "gallons per hour"

Still problematic because the "hour" unit is so long relative to human perception. Something more like "teaspoons per second" sampled every second.