How much usable kWh of energy does the battery really hold?

[RobbertPatrison]

I have a 2022 extended range MME that I love.

TLDR; If I change it full to 100%, I do not seem to get the promised 91kWh usable battery energy. It appears to be less. The GoM also shows sub-par range. So I started digging a little to find the cause. For now, it appears that the battery actually holds less energy and the GoM is hopelessly pessimistic.

In more detail: This is what the dashboard showed this morning after fully charging it:

• Battery: 100%
• Range: 259 Miles (= 7% worse than EPA) This is the Guess-o-Meter (GoM). I live in Silicon Valley with great weather in the 70-80ies, so I cannot blame the temperature.
• Lifetime usage: 3.3 miles/kWh (= 10% better than EPA) after ~2000 miles driven.

It is weird that the GoM shows such a low range given that the weather is in the 70ies here and that my lifetime efficiency is way better than the EPA number (3.3 vs 3.0 miles/kWh EPA). So, why am I not seeing better GoM values?

A clue could be that the data that I read using an OBD2 dongle and the Car Scanner app tells a somehat different story. It seems there is less usable battery capacity:

• HVB SoC: 93.71% (6% less than 100% !?!?!) This is the High Voltage Battery State-of-Charge.
• Energy to Empty: 88.47 kWh (3% less than the official 91kWh). This is what the MME thinks it has stored as usable energy.
• HVB Voltage: 388.93 V
• Cell module voltage: 4.14 V (There are 94 cell groups in series, so that matches HVB Voltage) That seems a typical value for Li-Ion Cells. In phones are driven harder to 4.2 Volt.

So it might be the case that charging stops before 100% charge is reached. Or that at the maximum cell voltage (4.14V) the energy stored is less than the usable 91 kWh that Ford claims. Nothing really adds up. Since I'm not sure which number to trust, let's go over the options:

• HVB Voltage: 388.93 Volt. This is likely a very accurate number. The charging stops when a certain voltage is reached to protect the battery. What voltage have others seen at a full charge? The question is: how much usable energy does the HV battery store at that voltage?
• Energy to Empty: 88.47 kWh. This should be the usable battery capacity at full charge. It appears 2.5kWh less than the rated 91kWh. The value is most likely calculated internally by measuring charge and discharge currents and tracking the battery voltage. I verified that this energy to empty is the value that the FordPass app uses for the data under 'my EV driving data'. So this seems to be legit.
• Another hint that the value is legit is the DC charger output power is 6.61kW at an L2 AC input power of 7.51kW. The added battery energy appears to increase by ~6.6kWh per hour using the Ford EVSE.
• HVB SoC: 93.71%. What is this, and why is it not the same as the value displayed on the dashboard?? This would imply that 100% is at 94kWh, which is neither consistent with the Ford usable 91kWh, nor with that the gross capacity of 98 kWh. Obviously, if Ford decides to raise the maximum voltage the SoC could be higher at the expense of more battery wear.
• The Guess-o-Meter: OK OK, I know this is based on past driving. But all my trip computer usage data shows better than 3.0 miles/kWh usage. At 3.0 miles/kWh we should get the EPA rated 276 miles out of 91kWh usable. Unless there is no 91kWh in the battery, of course. I cannot get the GoM anywhere near the EPA rated value of 276 miles even when I drive I drive like an old lady and the weather is very mild and the heater is off. I reset the history: no meaningful effect. Thie GoM is either unreasonably pessimistic, or it is based on a reduced battery capacity. Or perhaps both? The battery is 2 months old so should be in top shape.

Does anybody else see similar data?

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[Maquis]

Rated battery capacity is at some reference temperature. Capacity varies with temperature, so unless you do all of your data collection at that specific temperature, you won’t come up with the rated number.

 

[mkhuffman]

I know you know, we all know, the GoM is not very accurate. It is the car's best guess. So throw that out. Take your 3.3 mi/kWh and multiply it times the Energy to Empty. You get 292 miles. From the data you provided, it looks like you are getting the advertised range, and more!

As for what Energy to Empty means: many have discussed this in the Forum and there are no clear conclusions, from what I can tell. I do know that the Energy to Empty figure changes depending on various factors including climate.

I measured 91 kWh to empty once using my OBDII scanner, and I am only supposed to have 88 kWh capacity. Often it is less than 88 kWh. Several times I have measured 88 kWh to empty, which makes sense, but the SoC was not 100%. When I measured 91 kWh Energy to Empty, the SoC was still not 100%. That was really confusing.

Most people believe (reasonably) that there is a buffer of 2-3 kWh when you reach 0% SoC Displayed. I have not tested it myself, but I believe this accurate. You can keep driving the car even when you reach 0% SoCD, that is proven.

 

[SnBGC]

I have a 2022 extended range MME that I love.

TLDR; If I change it full to 100%, I do not seem to get the promised 91kWh usable battery energy. It appears to be less. The GoM also shows sub-par range. So I started digging a little to find the cause. For now, it appears that the battery actually holds less energy and the GoM is hopelessly pessimistic.

In more detail: This is what the dashboard showed this morning after fully charging it:

• Battery: 100%
• Range: 259 Miles (= 7% worse than EPA) This is the Guess-o-Meter (GoM). I live in Silicon Valley with great weather in the 70-80ies, so I cannot blame the temperature.
• Lifetime usage: 3.3 miles/kWh (= 10% better than EPA) after ~2000 miles driven.

It is weird that the GoM shows such a low range given that the weather is in the 70ies here and that my lifetime efficiency is way better than the EPA number (3.3 vs 3.0 miles/kWh EPA). So, why am I not seeing better GoM values?

A clue could be that the data that I read using an OBD2 dongle and the Car Scanner app tells a somehat different story. It seems there is less usable battery capacity:

• HVB SoC: 93.71% (6% less than 100% !?!?!) This is the High Voltage Battery State-of-Charge.
• Energy to Empty: 88.47 kWh (3% less than the official 91kWh). This is what the MME thinks it has stored as usable energy.
• HVB Voltage: 388.93 V
• Cell module voltage: 4.14 V (There are 94 cell groups in series, so that matches HVB Voltage) That seems a typical value for Li-Ion Cells. In phones are driven harder to 4.2 Volt.

So it might be the case that charging stops before 100% charge is reached. Or that at the maximum cell voltage (4.14V) the energy stored is less than the usable 91 kWh that Ford claims. Nothing really adds up. Since I'm not sure which number to trust, let's go over the options:

• HVB Voltage: 388.93 Volt. This is likely a very accurate number. The charging stops when a certain voltage is reached to protect the battery. What voltage have others seen at a full charge? The question is: how much usable energy does the HV battery store at that voltage?
• Energy to Empty: 88.47 kWh. This should be the usable battery capacity at full charge. It appears 2.5kWh less than the rated 91kWh. The value is most likely calculated internally by measuring charge and discharge currents and tracking the battery voltage. I verified that this energy to empty is the value that the FordPass app uses for the data under 'my EV driving data'. So this seems to be legit.
• Another hint that the value is legit is the DC charger output power is 6.61kW at an L2 AC input power of 7.51kW. The added battery energy appears to increase by ~6.6kWh per hour using the Ford EVSE.
• HVB SoC: 93.71%. What is this, and why is it not the same as the value displayed on the dashboard?? This would imply that 100% is at 94kWh, which is neither consistent with the Ford usable 91kWh, nor with that the gross capacity of 98 kWh. Obviously, if Ford decides to raise the maximum voltage the SoC could be higher at the expense of more battery wear.
• The Guess-o-Meter: OK OK, I know this is based on past driving. But all my trip computer usage data shows better than 3.0 miles/kWh usage. At 3.0 miles/kWh we should get the EPA rated 276 miles out of 91kWh usable. Unless there is no 91kWh in the battery, of course. I cannot get the GoM anywhere near the EPA rated value of 276 miles even when I drive I drive like an old lady and the weather is very mild and the heater is off. I reset the history: no meaningful effect. Thie GoM is either unreasonably pessimistic, or it is based on a reduced battery capacity. Or perhaps both? The battery is 2 months old so should be in top shape.

Does anybody else see similar data?

One days data does not make a full report. Charge to 100% displayed for 7 or 10 days in a row and you will see kWh to empty varies.

 

[Mach-Lee]

I have a 2022 extended range MME that I love.

TLDR; If I change it full to 100%, I do not seem to get the promised 91kWh usable battery energy. It appears to be less. The GoM also shows sub-par range. So I started digging a little to find the cause. For now, it appears that the battery actually holds less energy and the GoM is hopelessly pessimistic.

In more detail: This is what the dashboard showed this morning after fully charging it:

• Battery: 100%
• Range: 259 Miles (= 7% worse than EPA) This is the Guess-o-Meter (GoM). I live in Silicon Valley with great weather in the 70-80ies, so I cannot blame the temperature.
• Lifetime usage: 3.3 miles/kWh (= 10% better than EPA) after ~2000 miles driven.

Make sure you check the pack temp next time. Pack needs to be at 25ºC to get 91 kWh usable. It's temperature dependent. Degeneration will take some away from that (e.g. 2% degradation 91*.98=89 kWh usable).

Internal SoC is just a number, don't pay attention to that. I assume 100% would be at 4.20V, but you should never charge the cells that high because of the degradation that happens. 4.15V is the limit. 0% displayed is set so you can drive to 0% indicated and still have enough power to go a couple more miles as an emergency buffer. I'm not sure if the 91 kWh includes the usage below 0 mi DTE or not, if it did that would account for about 3 kWh. Depends on Ford's definition of "usable". 91-3 = 88 kWh from 100% to 0%, 3 kWh emergency buffer until cutoff, which leaves a little bit for pack safety.

Ford could have just changed their definition of usable for 2022, who knows.

 

[kltye]

Lithium-ion cells are considered "100%" of capacity when the (resting) voltage hits 4.2v. The SoC you're seeing is the actual pack SoC, as opposed to the SoC displayed (which is another OBD value that exists, which matches what you see on the IPC). Since we don't charge all the cells to 4.2v to extend the lifespan of the pack, you'll never see "100%" as the pack SoC. There are state of charge charts out there that show you the battery SoC vs cell voltage, if you really want to know what 4.14v is in %.

Energy to empty has never been reliable for me, even from the days of my C-Max Energi, so I'd ignore it.

Best way to test capacity is to charge the car to 100% (preferably on L2 charging), and then drive it all the way to 0% where the car shuts off (I guess you could leave it running with some sort of climate control on in your garage once you've hit 0%, if you don't want to be stranded...) Then, charge it with any method (again, preferably L2) that tells you how many kWh was dispensed when the SoC displayed reaches 100%. It'll probably be some amount >91 kWh, since there will be losses either through the cabling (if using DCFC), or the car's internal rectifier (if using L2). I would guesstimate between 10-15% loss during the entire charge session.

Unfortunately, as alluded to above, figuring out pack energy stored is a bit of an art as it is a science, since lots of variables affect the capacity, but it shouldn't vary wildly.

 

[RobbertPatrison]

Thanks for the feedback and suggestions. A lot of valid points. I will measure a few more times to see how the parameters change over time and with temperature. It still nags me that the GoM value is so out of whack compared to the other data. There is much more variance than what I saw in my Chevy Bolt.

The car stops charging when the first cell group reaches to upper threshold (4.14V apparently). I did not expect that to change much with battery temperatures in the range 18C-23C that I see. That would appear to be almost in the Goldilocks zone for Li-ion.

The battery is empty when the first cell group reaches the lower threshold (3V?). Since I never drove it down that deep the usable energy is possibly not well calibrated. Indeed, Ford may use an odd definition of ‘Usable’ here if it includes the safety margin below 0%.

The difference between these two extremes should be the usable energy. That is indeed malleable.

By constantly measuring battery voltage and current the algorithm should be able to tally the state of charge and the true “energy to empty”. At the same time it can see the SoC-Voltage curve to calibrate that. It was pretty accurate on the Bolt. I’m not sure how it is done in the MME.

 

[mattmarox]

Recent level 2 charge!

 

[mattmarox]

Should say this is extended range awd premium 6/21 delivery in Florida city driving primarily.

 

[Vinstang]

I also recently got an Extended Range (AWD) that seems to be getting much less range than it should. I similarly checked my battery capacity, and it says only 84.3 kWh. My range estimates have always been below 230 miles despite my driving efficiency averaging over 3 mi/kWh, so I'm suspicious something seems off with mine.

 

[nitinkumar00]

I don’t get why people stress so much about GOM. Ford wants to tell you worst than actual range just to be safe. So just drive normally not too harsh and look at your history. That’s all that matters.

 

[mkhuffman]

I also recently got an Extended Range (AWD) that seems to be getting much less range than it should. I similarly checked my battery capacity, and it says only 84.3 kWh. My range estimates have always been below 230 miles despite my driving efficiency averaging over 3 mi/kWh, so I'm suspicious something seems off with mine.

How did you check your battery capacity? Using a OBDII scanner at 100% SOCD? I have done that quite a few times and it varies between the low 80s and as much as 91. The difference is purely due to the environment and exterior temperature. In the winter I saw 82 kWh and in the summer around 89 kWh.

 

[Vinstang]

How did you check your battery capacity? Using a OBDII scanner at 100% SOCD? I have done that quite a few times and it varies between the low 80s and as much as 91. The difference is purely due to the environment and exterior temperature. In the winter I saw 82 kWh and in the summer around 89 kWh.

Yep, exactly, an OBDII scanner at 100% charge (while at 65 degrees). Oh, that's really helpful to know – I wouldn't have expected the capacity to fluctuate so much. I'm still not feeling great that my capacity in fairly warm weather is closer to yours in the winter, but maybe if I check again in a few months it'll be higher.

 

[mkhuffman]

Yep, exactly, an OBDII scanner at 100% charge (while at 65 degrees). Oh, that's really helpful to know – I wouldn't have expected the capacity to fluctuate so much. I'm still not feeling great that my capacity in fairly warm weather is closer to yours in the winter, but maybe if I check again in a few months it'll be higher.

I think it is very likely your estimated battery capacity will increase over time, especially in the summer. I doubt you have a battery capacity issue, but I suppose anything is possible. Check a few more times and report back on what you find.

 

[MailGuy]

The Bolt is definitely tighter with its usage. Speaking from experience as a new EV driver once upon a time, zero means zero .

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