Running the Battery to 0%

[MickeyAO]

I started a whole thread about this observation. I could not fathom an explanation why, after charging to 100%, I was consistently able to drive 6-10 miles and still be at 100% on the display. My only hypothesis was that Ford had unlocked added capacity, allowing the vehicle to charge beyond 131 kWh. So I asked the question on the forum whether this could be, and asking for other possible answers.

What I got in reply was all over the board, but no one came up with an explanation. When I kept asking the question, I kinda took a beating. The conclusion was basically that my observations must be wrong. Ad hominem attacks. (I did get a personal apology from one of them in a DM.) You can read the thread if you wish. (You will see in my first post that my second hypothesis was the correct one.) It was closed by admin but still exists.

Anyway, this was before I had an OBD scanner, and before I knew the difference between actual state of charge (HVB SOC, as read by the OBD scanner) and displayed state of charge (HVB SOC Display, shown on the dash and also by the scanner as the same data). It was also before I knew that 100% charge did not necessarily equate to 131kWh.

I'm having trouble loading images, but here's what I found.

After charging fully, the scanner showed

Energy 126.18 kWh (not 131); HVB SOC Display 100%; HVB SOC 94.83%

I do not recall how far I drove before the HVB SOC dropped (on the OBD scanner and on the dash simultaneously) below 100%, but I think it was about 8 miles. At that point it showed

Energy 121.74 kWh; HVB SOC Display 99.5; HVB SOC 92.06%

The findings were that a) the truck thought it was 100% charged when the battery had less than 131 kWh (my second hypothesis); and b) there was hidden energy above the HVB SOC Display reading. I used 2.55 kWh of battery before the display dropped below 100%.

I'm relating this for two reasons. One because several people reported the same finding that I had, but had no explanation. When the thread was closed, I could not report there, so I am reporting here. The second reason is to say that scientific knowledge is not the same as sound reasoning.

I appreciate the contributions of those who have put forth useful information. I have learned a lot here. I have narrowed my "delta" (charging more frequently) in order to preserve battery life. I will avoid going below 20% charge when possible. However, I advise people to take the information given them on the forum and apply your own knowledge to reach your own conclusions and decide how you use your truck.

Best to all involved, and no hard feelings. Not trying to take a victory lap here. Just trying to further knowledge.

I would suggest that someone with the time and an OBD reader map out the voltages of each SOC.

It can be cumbersome using the method we do to map a cell, but basically you drive it until you are down 10%, wait an hour, read the voltage.

One thing to keep in mind when observations based on displayed SOC are made is the polarization once the load is removed from the battery pack, and that the SOC is most likely based on observed voltage.

It is quite possible that the polarization of the battery pack (voltage going back up after you stop driving) can cause people to misinterpret what the dash is displaying and what they think it should be saying.

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[MickeyAO]

I would suggest that someone with the time and an OBD reader map out the voltages of each SOC.

It can be cumbersome using the method we do to map a cell, but basically you drive it until you are down 10%, wait an hour, read the voltage.

One thing to keep in mind when observations based on displayed SOC are made is the polarization once the load is removed from the battery pack, and that the SOC is most likely based on observed voltage.

It is quite possible that the polarization of the battery pack (voltage going back up after you stop driving) can cause people to misinterpret what the dash is displaying and what they think it should be saying.

BTW, the polarization is not done after 1 hour, but it is the method in the standard. When we do manufacturing tests on all the cells before binning for what cell goes through what test, we wait 24 hours after both the charge to 100% SOC (actual) and discharge to 0% SOC (also actual). Then we use a time constant to determine the actual polarization time.

So if you want to know the TRUE polarization for each SOC, drive 10% of displayed (or actual if you have an OBD dongle), wait 24 hours, record the voltage and do it over again. Same with charging.

 

[Box Cat]

I would suggest that someone with the time and an OBD reader map out the voltages of each SOC.

It can be cumbersome using the method we do to map a cell, but basically you drive it until you are down 10%, wait an hour, read the voltage.

One thing to keep in mind when observations based on displayed SOC are made is the polarization once the load is removed from the battery pack, and that the SOC is most likely based on observed voltage.

It is quite possible that the polarization of the battery pack (voltage going back up after you stop driving) can cause people to misinterpret what the dash is displaying and what they think it should be saying.

Haha, I started doing it and already have a few.
But it'll take me sometime to get to 0 since I don't drive many commute miles.
So, you're saying to keep recording after stopping for say, an hour?
Just saw the updated post. I suppose I could record next day before leaving but by that time some juice will have been consumed to recharge the LVB ...

 

[MM in SouthTX]

I am not educated enough on batteries to know how voltage relates to stored energy, but I do have the 4 readings on my one drive as the energy dropped 2.55 kWh.

391.5 V and 126.18 kWh
390.5 V and 124.29 kWh
391.0 V and 123.82 kWh
390.5 V and 121.74 kWh

I realize it would take a lot more data to discern a trend.

 

[MickeyAO]

I am not educated enough on batteries to know how voltage relates to stored energy, but I do have the 4 readings on my one drive as the energy dropped 2.55 kWh.

391.5 V and 126.18 kWh
390.5 V and 124.29 kWh
391.0 V and 123.82 kWh
390.5 V and 121.74 kWh

I realize it would take a lot more data to discern a trend.

Was that while driving or or after the polarization had time to settle down?

 

[MM in SouthTX]

Was that while driving or or after the polarization had time to settle down?

While driving. Charging to 100% tonight and will take some more screenshots at beginning and end of my drive and when I get in to drive home after it sits.

 

[MickeyAO]

There are two types of voltage curves. The first is usually expressed as voltage by Ah discharge or charge. This is a continuous load on the cell either to Vmin or Vmax. The other is an OCV (open circuit voltage) which allows a short time for the polarization to somewhat stabilze before the reading is taken (the standard is 1 hour but we use 24 hours for a specific test).

 

[MM in SouthTX]

There are two types of voltage curves. The first is usually expressed as voltage by Ah discharge or charge. This is a continuous load on the cell either to Vmin or Vmax. The other is an OCV (open circuit voltage) which allows a short time for the polarization to somewhat stabilze before the reading is taken (the standard is 1 hour but we use 24 hours for a specific test).

I charged to 100% last night and got the same result. I drove 5.6 miles to work this morning. I used 2.16 kWh but the display still says 100%. It will probably still say 100% after I drive home.

All of this supposition about fluctuating voltage is really not relevant because we don’t see the hidden usage happen when we start driving at 90% or 80%. The finding is that the truck is charging beyond what the display reports as 100%. There is hidden energy storage above the 100% displayed that didn’t used to be there.

 

[Grease Lightning]

Why are they overcharging the cell?

As Tim “the tool man” Taylor would say

 

[DesertEV]

BTW, the polarization is not done after 1 hour, but it is the method in the standard. When we do manufacturing tests on all the cells before binning for what cell goes through what test, we wait 24 hours after both the charge to 100% SOC (actual) and discharge to 0% SOC (also actual). Then we use a time constant to determine the actual polarization time.

So if you want to know the TRUE polarization for each SOC, drive 10% of displayed (or actual if you have an OBD dongle), wait 24 hours, record the voltage and do it over again. Same with charging.

Appreciate all your input. I do find it hard to believe that you will never go less than 20%. If you go on most road trips with it you are going to come into a situation where you need to go below 20%.

 

[Traconesu]

Ford shipped exactly that adapter with early Lightnings. I got one - you didn't? Mine is bright yellow and was in the lower compartment of the frunk at delivery.

My dealer took mine, as it was a mannequin and I had to wait 6 months to take possession of it. They told me it didn't come with one. But the first time I test drove it had one in the frunk.

 

[Grease Lightning]

If you go on most road trips with it you are going to come into a situation where you need to go below 20%.

Not always the case. In a lot of the US you could avoid the DCFS charging desert. With access to Superchargers and the RAN later this year, those desert are drying up even more. Assuming 85 kW available, that means around 170-190 miles of range. Totally doable. To get the higher number stay until 85% as that is the huge cliff.

 

[DesertEV]

Not always the case. In a lot of the US you could avoid the DCFS charging desert. With access to Superchargers and the RAN later this year, those desert are drying up even more. Assuming 85 kW available, that means around 170-190 miles of range. Totally doable. To get the higher number stay until 85% as that is the huge cliff.

Thanks. Can you explain your last statement? Just trying to understand what you mean.

 

[Grease Lightning]

Thanks. Can you explain your last statement? Just trying to understand what you mean.

Unless you are conservative in your driving techniques, to see 190 on a highway road trip you would likely need to charge between the 20% and 85% SOC. Since the lightning still hold 50 kW at 80-85% you can wait about 8 minutes for that last 5% if you needed the extra 10-15 miles for a buffer.

 

[DesertEV]

Unless you are conservative in your driving techniques, to see 190 on a highway road trip you would likely need to charge between the 20% and 85% SOC. Since the lightning still hold 50 kW at 80-85% you can wait about 8 minutes for that last 5% if you needed the extra 10-15 miles for a buffer.

Thanks. I have the extended range so that does not apply to me right?

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