Best way to quantify loss of usable battery?

[Halodde]

I posted something similar previously but am now asking for feedback from the group on this subject particularly from those who have driven EVs for many years and those who have ties to Lucid. What is the best way to determine loss of usable battery accurately? The only information I have is the obvious data provided by the car displays. This morning, for example, I left the house at 100% and drove (on the highway) nonstop. When my range was at 50% remaining, the 'since last charge' reading displayed that I had used 40 kWh. Assuming the readings are accurate, this implies that my usable battery is only 80 kWh. If this is the case, I've lost about 13% of the initial usable 92 kWh.

So my follow up questions are:
1) Is this the best way to quantify the loss?
2) Does anyone know if this is how Lucid calculates loss of battery capacity as it applies to the warranty?

Thanks in advance for your input.

 

[DeaneG]

Interesting. It doesn't make any difference, but I'm used to seeing battery health or capacity on the vertical axis, with miles or months on the horizontal axis.

 

[Bus Driver]

Interesting. It doesn't make any difference, but I'm used to seeing battery health or capacity on the vertical axis, with miles or months on the horizontal axis.

Now that you mention it, true. One of my high school algebra teachers had something about “‘time’ always being along the horizontal axis”.

 

[DeaneG]

Now that you mention it, true. One of my high school algebra teachers had something about “‘time’ always being along the horizontal axis”.

The dependent variable (battery % SOH) belongs on the vertical axis, because it's easier to understand visually: to think about a near-horizontal line vs a near-vertical line. The independent variable is on the horizontal axis (time, temperature, miles, number of DC fast charges, etc).

 

[xponents]

Now that you mention it, true. One of my high school algebra teachers had something about “‘time’ always being along the horizontal axis”.

As a high schooler having done Algebra in middle school, time is usually on the x axis, but that is not a strict rule. The independent variable would be on the X, and the dependent on the y. Since the miles would logically be the most independent factor affecting battery capacity, that should be on the X axis as you said!

 

[xponents]

The dependent variable (battery % SOH) belongs on the vertical axis, because it's easier to understand visually: to think about a near-horizontal line vs a near-vertical line. The independent variable is on the horizontal axis (time, temperature, miles, number of DC fast charges, etc).

Oops! You responded at the same time as me, but we said the same thing!

 

[segbrk]

Sorry everybody, I let my mathematical incompetence show. I suggest you take your screen and rotate it 90 degrees, then pretend I know what I’m doing.

 

[Halodde]

Just to wrap this up with a nice little bow, here's an update for anybody interested. Today although it wasn't one continuous drive like the other day, when my display showed 50% battery remaining, my since last charge information showed that I had used 42 kilowatt hours. So my conclusion is that the information displayed is not accurate either from the percent battery remaining or from the kilowatt hours used in the since last charge display.

 

[momo3605]

Just to wrap this up with a nice little bow, here's an update for anybody interested. Today although it wasn't one continuous drive like the other day, when my display showed 50% battery remaining, my since last charge information showed that I had used 42 kilowatt hours. So my conclusion is that the information displayed is not accurate either from the percent battery remaining or from the kilowatt hours used in the since last charge display.

Yup, you're probably right. I think the Out Of Spec guys when they did the range test found that in one instance the car was losing power well before 0 miles remaining on the dash and the next time it flew straight through 0 and started losing power after. So definitely a little bit of inconsistency in the miles remaining

 

[Adnillien]

Just to wrap this up with a nice little bow, here's an update for anybody interested. Today although it wasn't one continuous drive like the other day, when my display showed 50% battery remaining, my since last charge information showed that I had used 42 kilowatt hours. So my conclusion is that the information displayed is not accurate either from the percent battery remaining or from the kilowatt hours used in the since last charge display.

Just for clarity, what SOC did you charge to during last charge?

 

[Halodde]

Just for clarity, what SOC did you charge to during last charge?

100 %. I had several days of long drives in a row so my charge limit had been set to 100%.

 

[Adnillien]

100 %. I had several days of long drives in a row so my charge limit had been set to 100%.

Your numbers imply 84 kWhr usable in your battery which may be accurate if it is cold out. Battery capacity decreases in cold temperatures.

 

[Halodde]

Your numbers imply 84 kWhr usable in your battery which may be accurate if it is cold out. Battery capacity decreases in cold temperatures.

I think it's somewhere in that range. Last week, the numbers implied 80 kWh usable and the API hack said it was 86 kWh. So at this point I am comfortable assuming mid 80's for usable capacity which seems reasonable after 11 months and 25k miles. Don't you think?

 

[Adnillien]

I think it's somewhere in that range. Last week, the numbers implied 80 kWh usable and the API hack said it was 86 kWh. So at this point I am comfortable assuming mid 80's for usable capacity which seems reasonable after 11 months and 25k miles. Don't you think?

I agree.

 

[Haggy]

I posted something similar previously but am now asking for feedback from the group on this subject particularly from those who have driven EVs for many years and those who have ties to Lucid. What is the best way to determine loss of usable battery accurately? The only information I have is the obvious data provided by the car displays. This morning, for example, I left the house at 100% and drove (on the highway) nonstop. When my range was at 50% remaining, the 'since last charge' reading displayed that I had used 40 kWh. Assuming the readings are accurate, this implies that my usable battery is only 80 kWh. If this is the case, I've lost about 13% of the initial usable 92 kWh.

So my follow up questions are:
1) Is this the best way to quantify the loss?
2) Does anyone know if this is how Lucid calculates loss of battery capacity as it applies to the warranty?

Thanks in advance for your input.

As a long time EV owner, I can tell you from the perspective of many years, but it doesn't necessarily translate to Lucid. With a Tesla, I found that the best way involves getting the battery down to a low level, charging to 100%, immediately using the car and going down to low, charging again and seeing what sort of range you get and what's displayed. Other owners were seeing a decade ago that it was effective.

I had a Model 3 that appeared to have lost a lot of range. A lot of it happened during Covid lock downs and when working at home meant that my wife hardly used it. We didn't use it for road trips. After years of thinking that I had a lot of range loss, I gave it to my daughter, who lives far away, meaning a long road trip, and multiple full to low charge cycles, after which I found that the range loss as displayed was about 8 miles compared to new.

In terms of usable range the way you are using the term, I don't have enough experience with the Lucid to contribute anything meaningful. But there are many factors that will determine how far you go on a charge, and overall, that's what's going to count the most. I think that it will take years before there's enough data to answer some of these questions.

 

[Haggy]

As a high schooler having done Algebra in middle school, time is usually on the x axis, but that is not a strict rule. The independent variable would be on the X, and the dependent on the y. Since the miles would logically be the most independent factor affecting battery capacity, that should be on the X axis as you said!

Correct that it's not a strict rule. Ultimately, it goes by what does the best job of conveying the information that you are trying to convey, in a format that would be the most comfortable for the person seeing the graph. In this case, the traditional guideline would work best, but it's not a strict mathematical rule. Since everything is labeled correctly, it's a valid graph and not a "mistake" per se, but swapping would have made it clearer. On the other hand, since my screen won't pivot, I can turn my head, or change my mode of thinking, so it's not a big deal.