Battery Confusion - How Much Battery Did I Use?

[Jimrpa]

This past Saturday, I went on a "mini road trip" from my home outside Philadelphia to Bethesda, MD (colloquially known as "the evil place" ?)

To prepare for the trip, I charged my car to 100%. My car stays in a garage at home. It's not heated, but it's usually in the upper 40s to low 50s. it was probably about 30 degrees when we left. I came up with the following information when I arrived at my destination (both from the IP and from the Trip meter):

IP Readings at start of trip (home):
Range: 275 miles
Battery: 100%
Odometer: 24,694.7 miles

IP Readings at destination in Bethesda:
Range: 49 miles
Battery: 28%
Odometer: 24,835.5 miles

Trip meter at destination in Bethesda:
Distance: 140.8 miles
Time: 2:57:34
Average energy use: 2.5 mi/kWh

Distance traveled per trip odometer:
24,835.5 miles - 24,694.7 miles = 140.8 miles

Distance traveled by range meter:
275 miles - 49 miles = 226 miles

Kilowatts-hours consumed per Trip odometer:
140.8 miles / 2.5 miles / kWh = 56.32 kWh

Percent of battery consumed:
100% - 28% = 72%

Usable battery capacity via distance traveled:
56.32 kWh / 0.72 = 78.22 kWh

Kilowatt-hours consumed per range meter:
226 / 2.5 miles / kWh = 90.4 kWh

Usable battery capacity via range meter:
90.4 kWh / 0.72 = 125.6 kWh

Distance traveled per range meter and “usable” battery capacity.
Battery capacity per my window sticker: 88 kWh
Current battery capacity: 91 kWh (I think. Supposedly Ford deployed an update to increase the usable capacity of MY21s, but I can't find that documented anywhere.)
Maximum battery capacity: 99 kWh

Window sticker battery used: 88 kWh * 0.72 = 63.36 kWh
Current capacity battery used: 91 kWh * 0.72 = 65.52 kWh
Maximum capacity battery used: 99 kWh * 0.72 = 71.28 kWh

Window sticker distance traveled = 63.36 kWh * 2.5 miles / kWh = 158.4 miles
Current capacity distance traveled = 65.52 kWh * 2.5 miles / kWh = 163.8 miles
Maximum capacity distance traveled = 71.28 kWh * 2.5 miles / kWh = 178.2

Things that don’t make sense:
Per the Range meter, I traveled 226 miles, yet per the odometer, I only traveled 140.8 miles?

I can't get the actual battery capacity using either distance traveled via the odometer (the computed capacity is low) or the distance traveled by the Range meter (computed capacity is too high).

Conclusion:
While I don't think it will ever be possible to get all of these values to align and reconcile, I suspect a lot of that's driving the errors is that the car was sitting in a warmer garage while charging, thus yielding an excessively optimistic value for range on the range meter.

Recommendation:
Ford should cross-check the ambient temperature via the in-vehicle against the forecast outside air temperature for the vehicle's location. If there's a significant difference between the temperate reported by the vehicle and the temperature forecast for the vehicle's location, Ford should use the temperature value that would yield the most conservative range estimate.

Thoughts? Anyone see anything wrong with my logic, assumptions, or math?

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[AKgrampy]

Sorry - more work than I will ever do! All I will point out is the range is called GOM “GuessO Meter” for a reason and it will shift and vary due to driving conditions.

 

[DugthePug Dad]

This past Saturday, I went on a "mini road trip" from my home outside Philadelphia to Bethesda, MD (colloquially known as "the evil place" ?)

To prepare for the trip, I charged my car to 100%. My car stays in a garage at home. It's not heated, but it's usually in the upper 40s to low 50s. it was probably about 30 degrees when we left. I came up with the following information when I arrived at my destination (both from the IP and from the Trip meter):

IP Readings at start of trip (home):
Range: 275 miles
Battery: 100%
Odometer: 24,694.7 miles

IP Readings at destination in Bethesda:
Range: 49 miles
Battery: 28%
Odometer: 24,835.5 miles

Trip meter at destination in Bethesda:
Distance: 140.8 miles
Time: 2:57:34
Average energy use: 2.5 mi/kWh

Distance traveled per trip odometer:
24,835.5 miles - 24,694.7 miles = 140.8 miles

Distance traveled by range meter:
275 miles - 49 miles = 226 miles

Kilowatts-hours consumed per Trip odometer:
140.8 miles / 2.5 miles / kWh = 56.32 kWh

Percent of battery consumed:
100% - 28% = 72%

Usable battery capacity via distance traveled:
56.32 kWh / 0.72 = 78.22 kWh

Kilowatt-hours consumed per range meter:
226 / 2.5 miles / kWh = 90.4 kWh

Usable battery capacity via range meter:
90.4 kWh / 0.72 = 125.6 kWh

Distance traveled per range meter and “usable” battery capacity.
Battery capacity per my window sticker: 88 kWh
Current battery capacity: 91 kWh (I think. Supposedly Ford deployed an update to increase the usable capacity of MY21s, but I can't find that documented anywhere.)
Maximum battery capacity: 99 kWh

Window sticker battery used: 88 kWh * 0.72 = 63.36 kWh
Current capacity battery used: 91 kWh * 0.72 = 65.52 kWh
Maximum capacity battery used: 99 kWh * 0.72 = 71.28 kWh

Window sticker distance traveled = 63.36 kWh * 2.5 miles / kWh = 158.4 miles
Current capacity distance traveled = 65.52 kWh * 2.5 miles / kWh = 163.8 miles
Maximum capacity distance traveled = 71.28 kWh * 2.5 miles / kWh = 178.2

Things that don’t make sense:
Per the Range meter, I traveled 226 miles, yet per the odometer, I only traveled 140.8 miles?

I can't get the actual battery capacity using either distance traveled via the odometer (the computed capacity is low) or the distance traveled by the Range meter (computed capacity is too high).

Conclusion:
While I don't think it will ever be possible to get all of these values to align and reconcile, I suspect a lot of that's driving the errors is that the car was sitting in a warmer garage while charging, thus yielding an excessively optimistic value for range on the range meter.

Recommendation:
Ford should cross-check the ambient temperature via the in-vehicle against the forecast outside air temperature for the vehicle's location. If there's a significant difference between the temperate reported by the vehicle and the temperature forecast for the vehicle's location, Ford should use the temperature value that would yield the most conservative range estimate.

Thoughts? Anyone see anything wrong with my logic, assumptions, or math?

Reading all that made my head hurt.

I just drive my car and enjoy it.

I don’t care about the efficiency.

I do enjoy the speed and fun.

 

[Maquis]

Remember that actual battery capacity varies with temperature, so it’s nearly impossible to reconcile numbers like you’re trying to do.
And don’t even try to use the range shown on the GOM to calculate anything.

 

[Mach-Lee]

Kilowatts-hours consumed per Trip odometer:
140.8 miles / 2.5 miles / kWh = 56.32 kWh

Usable battery capacity via distance traveled:
56.32 kWh / 0.72 = 78.22 kWh

This is the proper way. The battery does not have 91 kWh when cold. More like 80-85 kWh usable. If you remote stated that might not be included in mi/kWh either. Aging also brings it down.

There is sometimes a “drop” in the percent display due to temp changes. Like you’re start out at 80% and it drops to 77% in less than a mile. The battery was actually at 77% the whole time but the range meter is stuck at the last value it was charged to. You didn’t actually use the 3%.

I use 80 kWh for calculations.

 

[ChasingCoral]

Distance traveled per trip odometer:
24,835.5 miles - 24,694.7 miles = 140.8 miles

Right. This is the distance you traveled.

Distance traveled by range meter:
275 miles - 49 miles = 226 miles

This is totally meaningless. You've been around long enough to know the Guess-o-Meter knows nothing about the environmental condition or speed at which you were going to travel.

What you don't say is what the estimated range was according to the Navigation software or the %SOC expected at arrival by the Navigation software. That has meaning. The GOM does not.

 

[Peugfan]

Fatal error in your range calculation. Range meter is not range travelled. It is an estimate of your future range at one point in time. The item that is most a accurate is your odometer mileage. Maybe the % Battery is the next most accurate. Hopefully the mi/kwh for the trip is accurate…who knows. Remember garbage in equals garbage out in calculations. Following the rest of your calculations gave me a headache. ?

 

[Jimrpa]

Okay, no battery advice, but what is this "evil place" stuff about Bethesda? Lol.

It is difficult to explain - in a past life, I and other coworkers had to frequently go down to MD/VA to customer facilities. We took to jokingly refer to the area as “the evil place” primarily because of the traffic.

 

[Jimrpa]

Appreciate all the explanations and feedback. Yep, I know the GOM isn’t to be relied upon. I was using this as my first “long distance trip” (I’m not counting the trip to St. Michael’s after I got the car due to logistics issues and unfamiliarity with so much about an EV). I was curious about whether the parameters that, ideally, should line up, actually did so (and they did not, as expected). I also was curious about how big the differences were between the “ideal world” and the “real world”.
I actually did put the destination into the navigation system, but I don’t recall a predicted charge level on arrival (I probably just wasn’t paying attention). Also, it wouldn’t have been valid because I take routes other than what the navigation system recommends to get down there (for example, NEVER take I-95 through Delaware, which all navigation systems love. You’re guaranteed to add at least 40 minutes to your total travel time. Also, I take a couple of little back roads in MD that cut off time. Things you learn over decades of having to do that drive ?)

 

[DYohn]

It's not a gas tank.

 

[SpaceEVDriver]

Several others have mentioned the issue. The battery is not a volumetric container. It's a chemical potential energy storage device. The extractable, usable chemical energy changes based on several factors, including its immediate temperature, its age, on how quickly it's providing energy (discharge rate).

The rated capacity is determined by the manufacturer based on a specific set of these and other parameter values.

Example (for illustration, not accuracy):
If you started at 88 kWh at an ideal temperature, and drive calmly such that you were discharging the battery at a rate of 22 kWh/hour, you might be able to get 100 kWh of energy from the battery. This isn't just increased efficiency, it's more energy extracted.

If you drive aggressively such that you discharge at a rate of >88 kWh/hr, you might only be able to get 80 kWh of energy from the battery.

For this parameter, I imagine an issue we had on old gasoline vehicle with a fuel pump on the crankshaft (RPM dependent fuel flow) and a pinhole in the fuel line. At low RPM, there's no fuel leak. But as the engine runs faster, the pressure in the fuel line increases and pushes more and more fuel out through the pinhole. Not only is the engine running less efficiently, but there's less fuel available to the engine.

 

[AEGinMD]

I've lived in & around Bethesda for nearly 40 years and have never heard it referred to (or thought of it) as 'the evil place.' Unlike the place a few miles away known as Capitol Hill...

 

[Jimrpa]

Several others have mentioned the issue. The battery is not a volumetric container. It's a chemical potential energy storage device. The extractable, usable chemical energy changes based on several factors, including its immediate temperature, its age, on how quickly it's providing energy (discharge rate).

The rated capacity is determined by the manufacturer based on a specific set of these and other parameter values.

Example (for illustration, not accuracy):
If you started at 88 kWh at an ideal temperature, and drive calmly such that you were discharging the battery at a rate of 22 kWh/hour, you might be able to get 100 kWh of energy from the battery. This isn't just increased efficiency, it's more energy extracted.

If you drive aggressively such that you discharge at a rate of >88 kWh/hr, you might only be able to get 80 kWh of energy from the battery.

For this parameter, I imagine an issue we had on old gasoline vehicle with a fuel pump on the crankshaft (RPM dependent fuel flow) and a pinhole in the fuel line. At low RPM, there's no fuel leak. But as the engine runs faster, the pressure in the fuel line increases and pushes more and more fuel out through the pinhole. Not only is the engine running less efficiently, but there's less fuel available to the engine.

Conceptually, I guess I knew this but never thought about it that way! Thanks!

So, here’s a potential paradox that I haven’t been able to solve (although I think I may know the answer):
If I took my escape with a 15 gallon tank, drove it until the tank ran dry, my car would weigh roughly 90 lbs less than when I started (assuming gasoline weighs 6 lbs/gallon). Yet, if I charge my Mustang Mach-Es battery to 100%, then drive until the battery is flat, the weight of my car will not have changed (and for the pedantic, please replace “weight” with “mass”). How is this possible?

 

[Jimrpa]

I've lived in & around Bethesda for nearly 40 years and have never heard it referred to (or thought of it) as 'the evil place.' Unlike the place a few miles away known as Capitol Hill...

It’s highly doubtful you’d be familiar with that nickname for specific parts of MD and VA. I wouldn’t worry about it and I mean no offense to your home (after all, I shouldn’t speak - I live in a suburb of Philadelphia ?)

 

[SpaceEVDriver]

Conceptually, I guess I knew this but never thought about it that way! Thanks!

So, here’s a potential paradox that I haven’t been able to solve (although I think I may know the answer):
If I took my escape with a 15 gallon tank, drove it until the tank ran dry, my car would weigh roughly 90 lbs less than when I started (assuming gasoline weighs 6 lbs/gallon). Yet, if I charge my Mustang Mach-Es battery to 100%, then drive until the battery is flat, the weight of my car will not have changed (and for the pedantic, please replace “weight” with “mass”). How is this possible?

It does change mass. But since we're (essentially) only moving electrons into and out of the battery, that mass is nearly immeasurable.

There's so much excess material in a gallon of gas that doesn't contribute to the useful energy. It all has to be managed, which is the entire purpose of the exhaust system and emissions control system of the vehicle.

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