Battery capacity estimator.

[EdY]

Picked up my Mach e gt PE at the start of the month and have about 600 miles on it. Love the car, but have noticed a large discrepance between the efficency calcuator an the precent change indicator.

As an example, I went for a quick drive last night of 22 miles, with an energy efficiency rating of 3.2 miles/kWh. This equates to 7kWh used. During this same trip, the battery capacity went from 70% state of charge to 60% state of change. This would seem to indicate that I used, 8.8 kWh was used??

Seems like the energy efficency calculator is way off, or my battery pack has only ~80% of the promised 88kwH usage capacity.

Has anyone else out there done this type of calcuation? I know the milage estimator isn't the best, but how about the capacity indicator. I would have thought that pack voltage would provide a pretty actuate esimate of energy capacity.

Sponsored

 

[benk016]

Picked up my Mach e gt PE at the start of the month and have about 600 miles on it. Love the car, but have noticed a large discrepance between the efficency calcuator an the precent change indicator.

As an example, I went for a quick drive last night of 22 miles, with an energy efficiency rating of 3.2 miles/kWh. This equates to 7kWh used. During this same trip, the battery capacity went from 70% state of charge to 60% state of change. This would seem to indicate that I used, 8.8 kWh was used??

Seems like the energy efficency calculator is way off, or my battery pack has only ~80% of the promised 88kwH usage capacity.

Has anyone else out there done this type of calcuation? I know the milage estimator isn't the best, but how about the capacity indicator. I would have thought that pack voltage would provide a pretty actuate esimate of energy capacity.

The better way to test would be to charge back up after your trip and see how much power it took to get the car back to 80%. Even that will have some margin for error because not 100% of the power delivered to the car goes into the battery.

 

[EdY]

The better way to test would be to charge back up after your trip and see how much power it took to get the car back to 80%. Even that will have some margin for error because not 100% of the power delivered to the car goes into the battery.

Ya, I did this but there are a lot of variables there as well. I am using the charger that came with the car on a 240v/50amp circuit. I have read that the charger actually pulls 30amps, but what is the efficency of getting that energy into the battery? 5, 10, 15% loss??? This is the same margin of error as the other calcuation method. If I assume 5% loss, then the battery capacity is probably pretty close to 88kWh. If it is 15% well then I am in that 70-80kWh area.

 

[phidauex]

Ya, I did this but there are a lot of variables there as well. I am using the charger that came with the car on a 240v/50amp circuit. I have read that the charger actually pulls 30amps, but what is the efficency of getting that energy into the battery? 5, 10, 15% loss??? This is the same margin of error as the other calcuation method. If I assume 5% loss, then the battery capacity is probably pretty close to 88kWh. If it is 15% well then I am in that 70-80kWh area.

The battery charging process is 96-97% efficient when using a home L2 charger (which squares with the internal efficiency of batteries of this type), so that shows you should be in the right zone with the energy charged from your trip.

 

[EdY]

The battery charging process is 96-97% efficient when using a home L2 charger (which squares with the internal efficiency of batteries of this type), so that shows you should be in the right zone with the energy charged from your trip.

So the ford pass app shows you the energy used for your trip under "my ev driving" . Does anyone else see that the Energy used doesn't match the decrease in the batteries capacity?

 

[Frank Katz]

We've had our Mach-E for 7 months but had made no big trips till this month. On one of them I check the mileage at the beginning and the range. Drove 150 miles or so and he range only went down 120. Interesting .

 

[EdY]

We've had our Mach-E for 7 months but had made no big trips till this month. On one of them I check the mileage at the beginning and the range. Drove 150 miles or so and he range only went down 120. Interesting .

So range not decreasing as fast as expected can be attributed to driving slower, in good moderate temps, etc. What I am complaining about is the claimed battery capacity of my car.

The claim is 88 kWh of usage energy in the pack. Tonight I drove through 20% of my pack. I went 50 miles. The trip computer claimed I was getting 3.1 miles per kWh. The ford pass app said I used 15.8 kWh of energy on this trip. 50/15.8 = 3.1 kWh, so that makes sense.

What is concerning is that 20% of my pack shouldn't be 15.8 kWh. It should be 17.6 kWh.

So either the trip computer is lying about the car's efficency, or my pack's usable energy is 79 kWh. Don't know what is worst. Note this trip was in 60 degree weather and 55-60 mph speeds

 

[phidauex]

So the ford pass app shows you the energy used for your trip under "my ev driving" . Does anyone else see that the Energy used doesn't match the decrease in the batteries capacity?

I haven’t looked at it closely, but yes, many people have reported that the energy used values in Journeys or in the trip computer don’t quite jive with the measurements. I’m not sure what the resolution is, but I don’t think the problem is that your battery is low capacity, those are rigorously tested by the manufacturer, but that the trip computer is still a big buggy/confusing on how it represents energy used.

 

[HuntingPudel]

There may be some rounding issues and/or other inaccuracies in the way things are being reported by the car to the FP app. Do you have an OBD scanner that has templates for the MME so you can record the actual energy usage, charge states, etc?

 

[JimmyMachE]

In most EVs the % SOC is linear in Ah, but not kWh.
As voltage drops, each per cent at the low SOC contains less kWh than per cents at the top. Not sure about MME, though, haven't checked yet.

Car Scanner ELM OBD2 app actually shows "Energy to empty" in kWh and it seems somewhat disappointing even at very high SOC. Not quite sure how reliable it is, and how many kWh remain in the battery at 0% SOC, never run it so low. Maybe it is just a rough estimate...

Mustang Mach-E profile should be selected in Car Scanner to get Energy to empty :

 

[EdY]

In most EVs the % SOC is linear in Ah, but not kWh.
As voltage drops, each per cent at the low SOC contains less kWh than per cents at the top. Not sure about MME, though, haven't checked yet.

Car Scanner ELM OBD2 app actually shows "Energy to empty" in kWh and it seems somewhat disappointing even at very high SOC. Not quite sure how reliable it is, and how many kWh remain in the battery at 0% SOC, never run it so low. Maybe it is just a rough estimate...

Mustang Mach-E profile should be selected in Car Scanner to get Energy to empty :

I do not current have access to a scanner, and I am a little concerned about downloading an app made by someone who lives at somewherestreet 18, Russia I am curious on what value it give for your car however.

 

[timbop]

So range not decreasing as fast as expected can be attributed to driving slower, in good moderate temps, etc. What I am complaining about is the claimed battery capacity of my car.

The claim is 88 kWh of usage energy in the pack. Tonight I drove through 20% of my pack. I went 50 miles. The trip computer claimed I was getting 3.1 miles per kWh. The ford pass app said I used 15.8 kWh of energy on this trip. 50/15.8 = 3.1 kWh, so that makes sense.

What is concerning is that 20% of my pack shouldn't be 15.8 kWh. It should be 17.6 kWh.

So either the trip computer is lying about the car's efficency, or my pack's usable energy is 79 kWh. Don't know what is worst. Note this trip was in 60 degree weather and 55-60 mph speeds

Your expectation in precision is the issue. The reported mi/kwh efficiency is rounded to tenths in increments: 3.0, 3.1, 3.3, 3.5, 3.7, etc. The computation of percentage left in the battery is based on voltage and not a meter that actually reads each kw pulled from the pack. Ford's software also tends to be conservative in its reporting because it doesn't want you to get stuck somewhere - it errs on the side of suggesting you charge sooner/more than you might actually need to.

You have an 88 kwh battery. The car's metrics aren't "lying" they are imprecise and intentionally conservative within the margin of error.

 

[EdY]

Your expectation in precision is the issue. The reported mi/kwh efficiency is rounded to tenths in increments: 3.0, 3.1, 3.3, 3.5, 3.7, etc. The computation of percentage left in the battery is based on voltage and not a meter that actually reads each kw pulled from the pack. Ford's software also tends to be conservative in its reporting because it doesn't want you to get stuck somewhere - it errs on the side of suggesting you charge sooner/more than you might actually need to.

You have an 88 kwh battery. The car's metrics aren't "lying" they are imprecise and intentionally conservative within the margin of error.

I agree I have the 88kwh battery. It is a GT PE after all. That said, it is not a rounding issue. I have done trips that used 50 to 70% charge and the "Journeys" data is consistent. For each 10% capacity I get 8kwh not 8.8kwh.

Now you may be right and ford's capacity gage might be like most gas tank gages where when it reads empty, you really have a gallon or two still in the tank. Since going to zero is hard on the battery I haven't done this experiment.

I think there are three possible explainations.

1. The trip computer is just too optimistic as to the efficency of the vehicle, and the stated miles/kwh is too high
2. The capacity gage is inacturate and if I cycle all the way to 0% I would find my missing 8kwh of energy.
3. I really do have 80kwh of usable energy and I got a battery that is down 10% its rated capacity right out the gate.

Now I tend to believe that the most likely scenario is number 1. That said, I see other GT PE owners claiming over 300miles of range based on their miles/kwh in their trip computers.

If I used my trip computer numbers I would be getting 260 to 270 miles range at 70 mph, and over 300 miles at 55-60mph. For my 100-30% runs, the actual milage was ~245 at 70, and 265 at 55-60mph.

The purpose of this thread was to solicit data from other owners to see if their kwh used in the EV driving data jived with what the capacity indicator was telling them. I my case there is a consistent 10% error, i.e. 80kwh, vs. 88kwh.

 

[JoeDimwit]

I have a round trip commute of 72 miles (36 miles each way), that routinely uses 21-22% of my battery pack. That works out to 3.89610ish M/KWh. My trip meter will show anywhere between 3.7-5.2 M/KWh depending on what drive mode I’m using, how traffic is moving, how much climate control I’m using, etc. but my battery percentage is always right around the same 21-22%. Until now, I haven’t had access to a smart charger to get charging data, so I’m stuck with the abysmal “data” ford thinks we are capable of understanding, so I plan to start checking the math based on the charger data over the course of several charges this week. Currently, because the numbers on the car don’t make sense (how can the consumption be the same when the M/KWh goes up 40%?), I don’t have much faith in any of the numbers right now. I need to verify before I can trust.

 

[AZBill]

I would suggest you do a longer range test with a higher percentage of battery used. In July, I took my CA Route 1 on a trip. I drove 183 miles and used 67% of my battery, so that is 59kWh. My trip odometer indicated I used 3.1 mile/kWh. 183/59 = 3.1 mile/kWh, very accurate.

Ford is likely using fixed point arithmetic in their software, which does have imprecision. That imprecision will create greater errors with low numbers, than with higher ones. There are also rounding errors when converting to BCD (binary coded decimal) for the displays. In many cases the mile/kWh display only increments in 0.2, rather than 0.1, which definitely indicates poor precision is being used in the software.

My Bolt displays the actual kWh used since the last full target charge. It also displays the miles driven since last full charge and it displays the mile/kWh in 0.1 increments. That is much better than what Ford displays, and provides a real indication of the capacity of the battery.

Sponsored