Help me understand battery consumption

[dfjkl]

There is some battery reserved that we dont get access to... just like an ICE car that has a gas tank thats 17 gallons, and you drive it till its empty and fill it and it only takes 15.9 or 16 gallons.

If


Never happened for me, in 39 years of driving, and I have driven my ICE cars many (MANY) times down to where the dashed lines show on mileage left, or the dial was UNDER the "E".

I actually ran out of gas about 300 feet from a gas station this time last year in my 435, saying "I can make it, I can make it", and had to push the car into the gas station with help from my son, who I called to help me, and when I filled it up I still did not get the rated gas tank capacity. It was roughtly 1/2 a gallon under.

Far cry from 1/4 of a tank, which is what the OP is essentially talking about. I've done math based in fuel capacity quite a few times (prepping me for an EV apparently) to ensure I've had enough fuel for trips. Tank capacity really doesn't lie in an ICE. Depending on how the fuel pick-up is positioned in some vehicles there is a chance you won't get every drop of fuel though. That's not reserved capacity though.

 

[AlanSubie4Life]

Sort of a partial experiment today:

Charged to 248, ran it down to 202 in a drive 12 hours later (started at 247 due to vampire). Drive was done in two segments so there probably were some small losses when parked

Used 10.57kWh according to last charge meter (miles * Wh/mi).

Calculates out to:

10.57*310/45 = 73kWh.

The calculation is prone to significant rounding error for a short trip like this (only 2 significant figures due to the rated range delta being only 45 with no decimal point...drive more than 100 miles and you get 3 sig figs). And it will tend to be on the low side due to vampire drain and other non-drive mode losses.

So pretty sure if someone does a controlled experiment (charge before leaving, etc, no stops), we’re going to extrapolate pretty close to 75kWh for a good battery. But maybe it’ll end up a little lower. Certainly it will be well above 70kWh.

 

[AlanSubie4Life]

Another longer sample period, with minimal phantom drain, and I spent very little time in park not doing anything, so getting very close to "correct" answer:

Rated range: Start: 210 miles End: 108 miles

Used: 268Wh/mi for 91.2 actual miles = 24.44 kWh

24.44kWh * 310 miles/(210-108) miles = 74.3kWh

So, based on this, the "usable" capacity of the battery pack appears to be very close to 75kWh as advertised, @animorph , @zanary

Actual pack capacity is probably slightly higher (I've seen a 78kWh number somewhere, but that's not all usable). Of course, all this above assumes the metering is accurate and not just scaled to make things "look" correct. But presumably no funny games being played...

(That 268Wh/mi was pretty surprisingly good, considering that I went up and then came down 4000 feet (net zero gain), I used some heat and I have a P3D+ - though averaging only 45mph or so - so I think 260Wh/mi is quite possible on slower rural highways with the P3D+!)

So @Redrick00 , I think I'd conclude that you can trust this meter, and it all makes sense, but it doesn't count vampire losses or energy you use while sitting in park (which can be particularly significant if you're using climate control). We already concluded this earlier in this thread...this is just a decent datapoint (still subject to some small rounding errors, but probably within 1%) to support that claim.

 

[tvansinden]

I drive 28 miles to and from work each day, on freeways, in traffic. It's been in the mid-40's (f) in the mornings and high 60's (f) in the evenings, and the A/C and/or heat are usually on. I accelerate fast on occasion, spend a very small percentage of my time idling at lights, and occasionally use Autopilot for acceleration/braking, but steer for myself.

I haven't done any of the kWh calculations many folks have discussed in this thread; I've only gone by the mileage range shown in the car. Consistently, I lose +50% of my possible mileage per trip. In other words, if the range says 245 miles when I get in the car, after I've driven my 28 miles either way, the range will now show ~203 miles. This seems to me like a very large, consistent discrepancy from the stated range. To me, it doesn't seem like mileage loss, but a significant potential mileage miscalculation on the part of the car's software.

Does anyone else have this much less "distance capacity"?

 

[AlanSubie4Life]

I drive 28 miles to and from work each day, on freeways, in traffic. It's been in the mid-40's (f) in the mornings and high 60's (f) in the evenings, and the A/C and/or heat are usually on. I accelerate fast on occasion, spend a very small percentage of my time idling at lights, and occasionally use Autopilot for acceleration/braking, but steer for myself.

I haven't done any of the kWh calculations many folks have discussed in this thread; I've only gone by the mileage range shown in the car. Consistently, I lose +50% of my possible mileage per trip. In other words, if the range says 245 miles when I get in the car, after I've driven my 28 miles either way, the range will now show ~203 miles. This seems to me like a very large, consistent discrepancy from the stated range. To me, it doesn't seem like mileage loss, but a significant potential mileage miscalculation on the part of the car's software.

Does anyone else have this much less "distance capacity"?

Yes. This is normal and expected. If you try really hard, it is even possible to use 120 miles of rated range to go 65 miles. (~500Wh/mi)

If you have the P3D+ with sticky tires that is part of your issue (though your discrepancy is relatively small so you might not have the P3D). The rest is heating. Turn off the climate control entirely on one day and see the difference it makes.

If you do the calculations in this thread you’ll find it all makes sense.

 

[tvansinden]

If you have the P3D+ with sticky tires that is part of your issue. The rest is heating.

If you do the calculations in this thread you’ll find it all makes sense.

I have the Long-Range option, no Performance stuff. I get that the car has a fairly different bunch of internal calculations to be done versus an ICE vehicle, but I wonder why even have the range displayed if it's so far off? I mean, is it really possible to get 310 miles out of one full charge? What circumstances are necessary for that?

 

[AlanSubie4Life]

Absolutely it is possible. Turn off the heat and don’t use the brakes. You should never have to use the brakes. Drive under 70mph. If you drive at 80mph you won’t make the rated range. Try to modestly draft off people but don’t follow closely especially if it is a pickup without mudflaps otherwise your windshield won’t last. It’ll help.

With the LR (RWD?) you should be able to make 310 miles driving under 70mph with no heat and no AC. No heat is more important than no AC. Seat heaters are fine, you can use them; less than 100W each.

However, to make 310 miles you have to do it all at once. If you look at the total over several days you have to deduct about 4 miles per day for vampire drain. Turn off your third party apps if you’re using them to get to 4 miles per day.

EDIT: yeah, you need the aero wheels. If you have the 19” wheel option it won’t cut it for 310 miles unless perhaps you’re driving quite slowly. It’s actually the tires plus the aero covers (nothing to do with the size of the wheel). Continentals aren’t quite as efficient as Primacy MXM4, as I understand it.

 

[M3BlueGeorgia]

I have the Long-Range option, no Performance stuff. I get that the car has a fairly different bunch of internal calculations to be done versus an ICE vehicle, but I wonder why even have the range displayed if it's so far off? I mean, is it really possible to get 310 miles out of one full charge? What circumstances are necessary for that?

I have LR-RWD and can easily get the EPA range in Metro Atlanta. That's equivalent to 241 Wh/mile.
But not with short trips, nor when the ambient temperature drops close (or below) freezing, nor for sustained 75+mph speeds.
I have the 18" Aero wheels, so that helps.

Drove to and from Atlanta Airport earlier in week and got 223 for a 70 mile roundtrip. Mostly freeway, but in heavy traffic so never really got above 73 mph. Ambient temperature in low 60s (F).

Having said that, I've also seen numbers in the mid to high 300s when dealing with cold and higher speeds.

 

[DR61]

I have the Long-Range option, no Performance stuff. I get that the car has a fairly different bunch of internal calculations to be done versus an ICE vehicle, but I wonder why even have the range displayed if it's so far off? I mean, is it really possible to get 310 miles out of one full charge? What circumstances are necessary for that?

The circumstances are the EPA test sequence (look it up on epa.gov). Drive that test sequence with no heating of the cabin and at 65-70F and you will get about 310 miles or much more with 18" stock tires and RWD. I can easily exceed the 240 Wh/mi level with my AWD to get rated range or better IF I turn off most of the heating and drive carefully, which I do rather frequently if not in a hurry.

Unlike ICE vehicles there is no significant waste heat available to heat the cabin, so any use of heating will reduce range. Just a fact of life for EV's. I consider the number on the battery icon like a fuel gauge on an ICE vehicle, not a range indicator. To get a range estimate, use the trip computer or the energy app.