Battery capacity estimator.

[JoeDimwit]

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.

I don’t disagree. My “concern” comes from the fact that M/KWh can vary by up to 40% while consumption seems unaffected.

We also don’t know when the battery meter changes states. Whenthe display goes from 72% to 71%, is the battery 71.99%, 71.49%, or 71.0%? There are legitimate rules that call for each option, but we don’t know which they are using, and that can be a significant difference when you’re talking about 22 units. It’s not enough to account for a 40% swing in M/KWh, but it could affect it by maybe 5%.

also, I plan on charging to 90% at work today, and going 2 days, which should be around 160 miles or so, and then doing the math. I also intend to do a couple 1 day cycles of charging to90% at work and doing the math on those as well. That should give me a fairly accurate read on MY commute consumption and efficiency.

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[EdY]

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.

I did do this. I did trips where I went from 100->50 and 100->30%. In both cases, the amount of energy used as per the EV driving logs in the Ford pass app stated that I used 40kwh, and 56kwh. The data in the Ford pass app has energy comsumed in 100ths of a Kwh, so I don't buy the "rounding errors" arguement.

Your car seems to be giving much more actuate results, or as I have said above, my battery has already degraded by 10% and it only has ~800 miles on it.

 

[AZBill]

I did do this. I did trips where I went from 100->50 and 100->30%. In both cases, the amount of energy used as per the EV driving logs in the Ford pass app stated that I used 40kwh, and 56kwh. The data in the Ford pass app has energy comsumed in 100ths of a Kwh, so I don't buy the "rounding errors" arguement.

Your car seems to be giving much more actuate results, or as I have said above, my battery has already degraded by 10% and it only has ~800 miles on it.

There is one more thing to consider, and that is the ambient temperature you are driving in. In colder temperatures the battery will have less usable capacity. But since it is not really the middle of winter yet, that is not so likely to be a factor.

 

[EdY]

There is one more thing to consider, and that is the ambient temperature you are driving in. In colder temperatures the battery will have less usable capacity. But since it is not really the middle of winter yet, that is not so likely to be a factor.

Agreed, I have been doing these runs in what I think are pretty close to ideal conditions for a Li Ion battery, i.e. 65ish degrees Fahrenheit. The energy lost to the external temperature was in the 3% range according to the trip computer. It doesn't make up for the 10% delta that I am seeing, but is is interresting. I wonder how Ford intergrates this into their calculations.

I think one of the problems as I see it is that the current info that they provide is just inconsistent. Note: I am not complaining about range or how inactuate the GOM is. I reallize that range just has too many variables that the car can only make a rough guess about. e.g. efficency of the driver, elevation changes, wind speed, etc.

I would "think" that energy used and battery capacity should be knowable to a much greater level of percision. That said, I am a computer and eletronics focused EE, not a power focused EE, nor Li Ion battery engineer.

One of my goals of this thread was to see what other owners are seeing in their cars and whether my vehicle is an outlier, or not.

 

[DYohn]

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?

Thay are not the same metric.

 

[EdY]

Thay are not the same metric.

So I would agree that capacity will vary with temperature. Care to elaborate on your comment?

 

[DYohn]

The "battery capacity display" is not absolute. It is not like a fuel tank. It, like the range estimator, varies with ambient temperature, battery temperature, driving style (which affects battery temperature,) age, and I am sure other factors not on the top of my head. It will go up and down based on variables not directly related to energy used nor to energy supplied through charging. In theory you could watch it change as ambient temperature changes while using zero energy to operate the vehicle, and as the battery ages what is 100% today will not be the same as 100% in six years. It's not an absolute metric that can be used to compare to anything else; it is a snapshot of current state and should be used as such..

 

[EdY]

The "battery capacity display" is not absolute. It is not like a fuel tank. It, like the range estimator, varies with ambient temperature, battery temperature, driving style (which affects battery temperature,) age, and I am sure other factors not on the top of my head. It will go up and down based on variables not directly related to energy used nor to energy supplied through charging. In theory you could watch it change as ambient temperature changes while using zero energy to operate the vehicle, and as the battery ages what is 100% today will not be the same as 100% in six years. It's not an absolute metric that can be used to compare to anything else; it is a snapshot of current state and should be used as such..

Agree with all these points, but all you seem to be saying is that temperature, leakage, and age affect battery capacity. That said, at ideal battery temperatures, driving within 5 hours after completing a charge and owning a car that is two weeks old, I consistently get 8kwh of energy per 10% of battery capacity. So by eliminating driving, temperature and leakage as factors to the best of my ability, I am left with inacturate capacity measurements , inacturate energy used measurements, or a battery pack in a brand new car that is behaving like it is serveral years old already.

Note that my calculations are very consistent. 80-81 kwh of usable capacity in the pack. I assume that as the temps get lower this winter, it will decrease further. I just don't like where I am starting out at.

I started this thread attempting to get some data from other owners, but it seems like no one is interrested in this calculation. Sigh

 

[DYohn]

A it seems like no one is interrested in this calculation. Sigh

That is likely correct.

My point is that the display showing capacity changes with the battery condition. It is not an absolute like Kwh used is. That, plus to me, it really doesn't matter as you have pointed out.

 

[EdY]

That is likely correct.

My point is that the display showing capacity changes with the battery condition. It is not an absolute like Kwh used is. That, plus to me, it really doesn't matter as you have pointed out.

So I agree that capacity changes with battery condition. I do not agree that no one should care! For a brand new vehicle, you should be able to expect the battery condition to meet factory spec in the ideal temperature range, i.e. 88kwh, at ~70 degrees Fahrenheit

I suspect that Ford's comsumption numbers are just overly optimistic, and therefore the efficency ratings in the trip computer are also optimistic. The same can be said of my F50 and fussion, both use more gas that the trip computer claims, resulting in mpg 5-10% greater that it really is.

Any idea was your car tells you?

 

[DYohn]

So I agree that capacity changes with battery condition. I do not agree that no one should care! For a brand new vehicle, you should be able to expect the battery condition to meet factory spec in the ideal temperature range, i.e. 88kwh, at ~70 degrees Fahrenheit

I suspect that Ford's comsumption numbers are just overly optimistic, and therefore the efficency ratings in the trip computer are also optimistic. The same can be said of my F50 and fussion, both use more gas that the trip computer claims, resulting in mpg 5-10% greater that it really is.

Any idea was your car tells you?

I honestly do not care about such things. If it's important to you then perhaps keep a log and develop a method for your own personal calculation gratification. Every vehicle is going to behave differently.

Me, I used to put gas in my vehicles when they needed it and today I charge my MME every night or every chance I gert if on the road. I really don't care about my MPG then or my MPkwh now.

 

[JimmyMachE]

Note that my calculations are very consistent. 80-81 kwh of usable capacity in the pack. I assume that as the temps get lower this winter, it will decrease further. I just don't like where I am starting out at.

Interesting, your 80-81 kwh calculations rougly correspond to the "HVB Energy to empty kWh" indication in Car Scanner Elm Obd2 or Torque Pro. I though it was just rough and unreliable estimate, as it fluctuated quite a bit, so I didn't pay much attention. But I never drove car battery to empty, so I don't know what the remaining "Energy to empty kWh" value is at 1% or 0% SOC.

Might be worth comparing in more cars at various mileage and ambient temperatures (if such factors indeed play a role).

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