OBD II Data for HVB

[larryh]

The following chart illustrates why you can't use the HVB voltage to determine SOC while driving.  Instead, you have to use ETE as described in the previous posts to estimate SOC while driving.  This is data collected during a 60 mile commute home. 

 

At 72% SOC, you can see the HVB voltage varied from 315 to 336 volts while driving.  That is quite a range. 

 

At 336 volts, the SOC varied from 72% to 94%.  At 315 volts, SOC varied from 48% to 76%. 

 

The more power consumed or regened to the HVB, the greater the voltage is from equilibrium.  Using voltage alone, one cannot accurately estimate the SOC of the HVB.  ETE must be used instead.  When the power output of the HVB is minimal, then voltage will be close to the equilibrium voltage, but there will still be error in the SOC if that value is used to compute SOC (the error will however be small, i.e. maybe 5%).

 

Edited June 6, 2015 at 01:39 PM by larryh

[rbort]

Of course Larry that makes sense, voltage drops with load.   That's why Gary was "supercharging", dropping the voltage of the pack with the car on with the AC and then having the car recharge the battery back to to a certain voltage limit which would end up higher once you turned the car off and removed the load.

 

When the car is at rest, the battery voltage will normalize and go to a certain figure which is relative to the charge level.  While driving, the car counts the amps coming out of the battery and gives you a soc indication that is related to how much came out of the pack versus the total capacity.  Its nothing new based on what I'm used, that's usually how these things work in other applications and I'm sure Ford does the same thing.

 

-=>Raja.

Edited June 6, 2015 at 02:41 PM by rbort

[Hybridbear]

Do you notice more variation while the car sits when you've used more of the HVB energy during a trip? When we do trips starting with a full HVB and use the entire battery up during the trip we see more variation than if we are only using part of the capacity.

[larryh]

The variation should be a percentage of the energy used from the HVB.  So the more energy used, the greater the variation.  The car will start correcting the ETE if voltages stray too far from what is expected.  Otherwise, the car will continue to update ETE based on the total energy drawn and regened back into the battery.  If it got the initial ETE at the start of the trip wrong, then ETE and SOC at the end of the trip will be wrong.  If the HVB warms up faster than expected or you use much higher levels of power from the HVB than expected, ETE will deviate more from the estimated ETE. 

[Hybridbear]

The variation should be a percentage of the energy used from the HVB. So the more energy used, the greater the variation. The car will start correcting the ETE if voltages stray too far from what is expected. Otherwise, the car will continue to update ETE based on the total energy drawn and regened back into the battery. If it got the initial ETE at the start of the trip wrong, then ETE and SOC at the end of the trip will be wrong. If the HVB warms up faster than expected or you use much higher levels of power from the HVB than expected, ETE will deviate more from the estimated ETE.

Makes sense. The biggest deviation we've seen in the Energi is when traveling well beyond EV range where we use all of the HVB in one trip.

 

The Focus Electric will adjust the ETE on the fly. I've had stretches where I'm using about 250-300 Wh/mi on the freeway but the ETE is only decreasing at a rate of about 50-100 Wh/mi. Then all of a sudden the ETE will self-correct and drop by 2500-3000 Wh and the predicted range will thus drop by about 10 miles in an instant.

[larryh]

I have recorded ETE (Energy to Empty) of the HVB each morning for the past two years.  The following chart shows ETE (normalized to 100% SOC) vs. temperature.  The blue markers are from last year.  The red markers are for this year.  You can see the the energy capacity of the HVB has decreased about 0.2 kWh from last year.  The car is just over 2 years old with 25,000 miles.  I don't have any data for the first year I owned the car, but I would have expected the capacity to be around 7.2 kWh that year.  The total degradation is then approximately (7.2 - 6.9)/7.2 = 4%. 

 

 

 

Edited June 12, 2015 at 03:04 PM by larryh

[jdbob]

I took some sporadic measurements since I got Forscan just to see how the battery temperature affects the ETE (normalized to 100% of course).

 

-1C = 6359

7C = 6556

10C = 6554

11C = 6531

13C = 6556

18C = 7139

19C = 7117

26C = 7202

 

Seems like there is a big jump between 13C and 18C, do you notice something similar? My car has about 22,000km on it.

[larryh]

You can see my data in post 127.  There should not be a jump between 13C and 18C.  You need to collect more data.  Also, make sure the battery has rested at least a couple of hours after charging or driving before recording the measurements. Otherwise, you will get inconsistent results.  The ETE starts dropping off rapidly below 10 F.   I collect the measurements in the morning before my drive to work.

Edited June 12, 2015 at 06:30 PM by larryh

[jdbob]

Some of those readings may have been after the car had been driven that day and recharged, in the winter that was the only way to get the higher battery temperature. Others may have been taken anywhere from 1 to 3 days after the battery charge cycle was completed. Preconditioning probably has an effect too. My readings are probably meaningless  :(

Edited June 12, 2015 at 07:34 PM by jdbob

[Hybridbear]

Some of those readings may have been after the car had been driven that day and recharged, in the winter that was the only way to get the higher battery temperature. Others may have been taken anywhere from 1 to 3 days after the battery charge cycle was completed. Preconditioning probably has an effect too. My readings are probably meaningless  :(

Add in the HVB SOC with your readings and you can create the same type of chart as Larry did. I've been collecting data for the past few months for the Energi and since FORScan for Android came out for the Focus Electric.

[jdbob]

Add in the HVB SOC with your readings and you can create the same type of chart as Larry did. I've been collecting data for the past few months for the Energi and since FORScan for Android came out for the Focus Electric.

 

I did, that's what I meant by normalized to 100%. For instance:

 

T=26C SOC=89.81% BAT_TO_EMPTY=6468

 

6468/0.8981 = 7202

[Hybridbear]

It's interesting how battery cooling behavior changes as the ambient temperature changes. A few days ago when I got home the battery temperature was 91 F, the ambient temperature was in the upper 80s and the car decided not to cool the HVB when I plugged it in. The car also was not running the fans while driving to cool the battery. Today with temperatures in the mid 60s with rain and the car was cooling the battery while I was driving even though it was only 77°. When I plugged the car in, the car immediately turned the fans on to cool the battery while waiting to charge.

[rbort]

Bear,

 

It probably has to do with the difference in temp between the battery and the outside air.  If its 88 outside and the battery is 91, there isn't much difference.  If its 65 outside and the battery is at 77, there is a bigger difference there.

 

The car has to figure what if its parked and the battery temp is the same as the OAT, even at 95F, running the fan is probably pointless.

 

-=>Raja.

[Hybridbear]

Bear,

 

It probably has to do with the difference in temp between the battery and the outside air.  If its 88 outside and the battery is 91, there isn't much difference.  If its 65 outside and the battery is at 77, there is a bigger difference there.

 

The car has to figure what if its parked and the battery temp is the same as the OAT, even at 95F, running the fan is probably pointless.

 

-=>Raja.

It absolutely does, I was just sharing my observation. In the winter the car will cool the HVB if it gets above 70 F. However, it should be remembered that when driving the car is using air conditioned air from inside the car to cool the HVB which is significantly cooler than outside air. Right now the outside temp is in the 60s but the air inside the car when I was driving was in the high 70s so the air it was taking in was no cooler than the HVB.

[rbort]

 

 

it should be remembered that when driving the car is using air conditioned air from inside the car to cool the HVB which is significantly cooler than outside air.

 

If the AC is on, if not its using outside air.

 

 

 

Right now the outside temp is in the 60s but the air inside the car when I was driving was in the high 70s so the air it was taking in was no cooler than the HVB. 

 

If the outside air is cooler than inside the car, doesn't the car take from that instead?

 

-=>Raja.

[Hybridbear]

If the AC is on, if not its using outside air.

 

 

 

If the outside air is cooler than inside the car, doesn't the car take from that instead?

 

-=>Raja.

I don't know. The HVB inlet temp PID is usually warmer than the inside temp.

[stevedebi]

If the AC is on, if not its using outside air.

 

 

If the outside air is cooler than inside the car, doesn't the car take from that instead?

 

-=>Raja.

Raja,

The battery compartment air intakes are inside the car, at least on the C-Max Energi. The external intakes are only used when plugged in for charging.

[Hybridbear]

Here is some additional info:

 

During high voltage charging the BECM commands the outside air (OSA) duct mode door actuator to open. This allows outside air to be pulled into the high voltage battery pack to cool SOBDM. The BECM monitors the mode door position and motor circuits and sets a DTC if a fault is detected. The SOBDM monitors its internal temperature and commands the charger cooling fan speed accordingly to prevent overheating.

 

The fan operation is controlled by the BECM based upon information received from thermistors located inside the High Voltage Battery. The BECM monitors the frequency returned to the BECM from the fan to determine actual fan speed. The control or feedback signal may be incorrect if the fan or wiring is at fault. The powertrain malfunction (wrench) warning indicator will illuminate when a fault condition is present.

 

Normal Operation and Fault Conditions 

With the ignition in the ON position and the engine running or OFF, the BECM monitors and maintains the High Voltage Battery temperature within a specific range. The High Voltage Battery has an external fan that circulates air within the High Voltage Battery so a specific temperature range is maintained. A thermistor is mounted to the battery case which monitors inlet air temperature along with 16 thermistors inside the High Voltage Battery which all monitor High Voltage Battery temperature. The ideal High Voltage Battery temperature is 25°C (77°F) with a desired range of 20°C (68°F) to 30°C (86°F). The BECM will shut the vehicle down and the powertrain malfunction (wrench) warning indicator will illuminate when the fault condition is present.

The High Voltage Battery is not designed to operate in temperatures below -40°C (-40°F). The BECM controls the temperature by adjusting the High Voltage Battery cooling fan speed.

This comes from info available in OASIS in the Workshop Manual.

Edited June 18, 2015 at 09:43 PM by Hybridbear

[larryh]

I think there are two fans for the battery, one that draws outside air and one that draws inside air.  There is only one BECM PID to indicate fan speed.  I think that refers to the one that draws in air from the passenger cabin.  There is also a BECM PID for door count to indicate whether the door for outside air is open or closed. 

[stevedebi]

I think there are two fans for the battery, one that draws outside air and one that draws inside air.  There is only one BECM PID to indicate fan speed.  I think that refers to the one that draws in air from the passenger cabin.  There is also a BECM PID for door count to indicate whether the door for outside air is open or closed. 

Larry,

I've not seen anywhere that the outside door is open except during charging of the HVB. It would seem counterintuative by Ford to open the outside vents during driving, since the entire design intent was that the driver would be using A/C during hot weather, to route cooler cabin air to the HVB.

Edited June 18, 2015 at 10:43 PM by stevedebi

[larryh]

The following chart shows what happens while charging the HVB with a 240 V charger.  I used value charging.  It decided to charge the battery until the displayed SOC was 30% for 40 minutes, and then continued charging the HVB the next morning for another 1:28 minutes (finishing more than hour before my GO time).

 

The red line shows the fan speed.  I assume this is the fan that draws in air from the cabin.  It ran from 4:57 pm to 5:08 pm.  The dark blue lines indicates if the inlet door for outside air is open or closed.  When the count/20 is below 95, it is open.  When it is above 110, it is closed.  The door remained open the entire time the HVB was charging.  Charging stopped and then the door closed at 5:36 pm.  I don't think there is a PID to indicate the speed of the fan that draws in outside air. 

 

The HVB temperature started out at 99 F and cooled to 97 F while charging.  The inlet temperature started out at 95 F and rose to 100 F.  The interior cabin temperature started at 90 F and rose to 91 F.  The outside temperature was 86 F. 

 

Note that value charging didn't continue to pull in outside air to cool the HVB after charging stopped.  That would have been useless since the inlet temperature was higher (100 F) than the HVB temperature (97 F).  That wouldn't provide very effective cooling. 

 

 

 

Edited June 19, 2015 at 12:23 AM by larryh

[Hybridbear]

Larry,

I've not seen anywhere that the outside door is open except during charging of the HVB. It would seem counterintuative by Ford to open the outside vents during driving, since the entire design intent was that the driver would be using A/C during hot weather, to route cooler cabin air to the HVB.

I wish it would switch if the outside air is cooler than cabin air. For example, suppose it's about 65 & sunny. At that temp you're probably driving with the HVAC off and windows down. The inside car temp is usually in the high 70s due to sunlight & thus cabin air being used to cool the HVB is in the high 70s. Here the outside air is at least 10 F cooler than the cabin air & it would be better to use outside air I'd think.

[larryh]

During my 60 mile commute last week, the fan that draws in interior air remained off until the HVB reached 102 F.  Then it remained on for the remainder of the trip.  The HVB stayed at 102 F.   The interior temperature was 92 F.  The outside temperature was 79 F.  The HVB inlet door temperature was 95 F. 

Edited June 19, 2015 at 12:49 AM by larryh

[Hybridbear]

During my 60 mile commute last week, the fan that draws in interior air remained off until the HVB reached 102 F. Then it remained on for the remainder of the trip. The HVB stayed at 102 F. The interior temperature was 92 F. The outside temperature was 79 F. The HVB inlet door temperature was 95 F.

Considering what Ford says regarding the preferred temp range being below 85 F I'm surprised that the car lets the HVB get so warm.

[rbort]

All what you guys posted here makes sense and sort of jived with what I expected.  The only interesting piece of information I found in there was the ideal temp range for the battery which I sort of gathered from the better range given by the battery in warmer weather, I just didn't know the exact figures.

 

When the car charges, it warms up the cabin.  It can be 60 degrees outside and in my garage and charge my car for a while and it feels like 80 inside.  The door is open and the car uses outside air to pump into the car over the battery while the vehicle is stopped and charging.

 

Larry, so you went from 99 to 97 while charging, very  close temp figures almost could be a read error on the sensors because the data can jump from what I've seen in your files in the past.  I wonder if you didn't charge how much would the battery have cooled over the hours overnight?  Do you have a chart that would show temp drop degrees per minutes so to speak?  Just curious as to how much difference the fan makes.  Also you can try fan with no charging as well to see what that yields.  Make a bigger value charge window later.

 

-=>Raja.

Edited June 19, 2015 at 02:39 AM by rbort