OBD II Data for HVB

[Hybridbear]

Today on my trip back to Minneapolis the HVB started out only in the 50s after sitting outside overnight and charging on L1 at the hotel. It never got above 65 F on my drive home and never above 60 during my driving around Wausau during the day. Thus the HVB fan never kicked on and the DCDC converter reported a temp of 174-176F for the entire trip after the initial warm-up.

[larryh]

The following chart shows the HVB Energy Capacity vs. HVB Temperature.  When the HVB temperature is around 100 F, the HVB can store approximately 7.2 kWh of energy.  When the HVB temperature is around 0 F, the HVB can store approximately 6.1 kWh of energy.  That represents a 15% loss of energy capacity when the HVB temperature falls from 100 F to 0 F.  Normally, the HVB temperature remains above 10 F (unless you leave the car outside overnight when the outside temperature falls well below 0 F).  At 10 F, the capacity loss is about 8%. 

 

However, normally you can get at most about 6 kWh of energy out of the HVB before the ICE will come on.  The car does not allow the HVB energy to fall below about 1 kWh.  When the HVB temperature falls to 0 F, you will only be able to get 6 - 1.1 = 4.9 kWh of energy out of the HVB before the ICE starts.  Thus the useable energy from the HVB has dropped about 20%.   And thus EV range drops by more than 20%.  EV range will drop by far more than 20% because it requires about 50% more energy to propel the car when the temperature is below 0 F (even if you do not use climate control to heat the car's interior).

 

Edited January 10, 2015 at 04:20 PM by larryh

[Hybridbear]

We experienced this while traveling. Each nice at the hotels we were able to plug in to 120V power. Each morning the HVB temp was down under 32 F and the ETE was 6.2 kWh or less. Now that we're in the desert with temps in the 70s the ETE after a full charge is about 7.1 kWh.

[jdbob]

I have a wifi OBDII port interface and use my iPad to monitor it using custom PIDs in the OBD fusion software. Normal PIDs work but not the custom Energi PIDs IHave found. Does anyone have a listing of a set of custom Energi PIDs that work on their software that I can port to OBD Fusion. I believe I can load Torque PIDs. Thanks for any pointers...

 

Just started playing around with OBD Fusion on an iPad. Found that the header value you need to specify is for what is received from the module, not what is sent. As an example for Inside Car Temperature:

 

ModeAndPID Name              Min  Max  Unit  Formula                 Header

22DD04     Inside Car Temp   0    300  F     (A*18-400)/10           7EC

 

On OBD Fusion set "Module/Header" to 7EC, not 7E4 that you would think. Whatever the normal header value is, looks like you need to add 8 for OBD Fusion. Set "OBD Mode" to 22, and "PID Number" to DD04.

[shaggy314]

So without reading all 7 pages of the is it better to slowly brake only, drive in L and less braking?

 

Is the electric motor better at charging the battery OR is the brake regeneration more efficient?

[larryh]

You want to let up on the accelerator and stop using energy from the HVB as soon as possible.  That means you want to coast to a stop sign while in Drive using the brakes as little as possible.  If you use L, you will use more energy from the HVB maintaining speed until you get closer to the stop sign, which you can never recover through regenerative braking.  You can see more about this starting here:

 

http://www.fordfusionenergiforum.com/topic/2566-efficient-ev-mode-driving-techniques/?p=17051

[stevedebi]

You want to let up on the accelerator and stop using energy from the HVB as soon as possible.  That means you want to coast to a stop sign while in Drive using the brakes as little as possible.  If you use L, you will use more energy from the HVB maintaining speed until you get closer to the stop sign, which you can never recover through regenerative braking.  You can see more about this starting here:

 

http://www.fordfusionenergiforum.com/topic/2566-efficient-ev-mode-driving-techniques/?p=17051

That has been my experience as well, with the exception of a sudden red light change. Then I use L to slow down. But not normally.

[larryh]

I have been tracking the estimated SOC of the 12 V battery as reported by the car each morning for the past several months.  The plot below shows the results.  I applied TSB 14-0020 in June 2014, which changed the programming used by the car to charge the 12 V battery.  So the SOC rose significantly after that date.  The estimate seems to be very noisy.  The average SOC seems to be around 90%.  I'm not sure what the expected SOC for the 12 V battery should be. 

 

Edited February 27, 2015 at 01:29 PM by larryh

[rbort]

Interesting.  I never applied that TSB to my car its the original programming and have not had any issues with the 12v battery except once when I forgot the parking lights on, they don't go out on their own apparently and they dropped its voltage low enough that the car was dead and I had to recharge it manually to bring the voltage back up over 10.5v before I could recharge it from the 120v charger.

 

It probably hurt the battery some being down to 8v but I have not addressed that.  Eventually I'll need to get a new battery but I only need this thing to close the contacts for the HVB.

 

-=>Raja.

[Hybridbear]

The highest Abs SOC I have seen when fully charged is 99.4%. Usually a full charge shows as somewhere between 7.05 & 7.15 kWh depending on HVB temp. Sometimes the charge is close to 7.2 kWh. Based on the Abs SOC & ETE reported by the car I do not detect any measurable capacity loss.

 

It seems that I get the highest ETE with HVB temps 72-75 F. Granted, since it's winter I don't really see HVB temps much warmer than that. But if I can keep the HVB temp in the upper 60s to low 70s when charging the ETE is higher when charging is completed.

[larryh]

I have been looking at data logged by Tesla owners with the 85 kW HVB.  At 0% SOC, the Tesla HVB voltage is 322 V and at 100% SOC, it is 405 V.   From Wikipedia, the 85 kWh battery pack contains 7,104 lithium-ion cells in 16 modules wired in series. Each module contains six groups of 74 cells wired in parallel; the six groups are then wired in series within the module.  From this, I deduce that there are 74 parallel connections of 7104/74 = 96 cells in series.  Thus the individual cell voltage varies from 322/96 = 3.35 V at 0% SOC to 405/96 = 4.22 V at 100% SOC.

 

For the Fusion Energi, the individual cell voltage ranges from 3.38 V at 0 % SOC (you can't actually drain the battery to 0% SOC) to 4.1 V at 100% SOC when the HVB temperature is around 100 F.

 

The 0% SOC levels for the cell voltages are approximately the same for the two cars.  However, the Energi does not allow you to discharge the cells below 14.5% SOC.  The Tesla allows you charge the cells up to 4.22 V (but the recommended maximum SOC is 80% which is about 4.05 V per cell).  The Energi only allows you to charge up to 4.1 V per cell.

 

Based on this information, the Energi seems to maintain the HVB SOC within a safe range to assure HVB longevity.  Now if only it could do a better job at controlling temperature. 

Edited March 21, 2015 at 12:57 PM by larryh

[murphy]

Only about 75 kWh of the 85kWh battery in a Tesla model S is available for use by the driver. 

That is for anti-bricking protection and probably to make sure that none of those 7,104 cells ever gets overcharged.

 

In day to day use they recommend not charging in excess of 90%. 

Charging to 100% for a trip is only to be done if the trip will start within a couple hours of charge completion.

[larryh]

Neither MFM or MFT allow us to set the maximum SOC for charging the HVB.  The car always charges to 100% (as displayed by MFM and MFT) which is about 4.1 V / cell.  We might be able to get a few miles more of range, on an occasional basis, if they would allows us to override the maximum charge to 4.2 V / cell right before we leave for a trip. 

Edited March 21, 2015 at 05:00 PM by larryh

[Hybridbear]

Last night I plugged in the Energi to charge for a bit while I used the Focus Electric to run errands. The HVB temp was in the low 40s at the time. According to MFM the SOC was 88% when I unplugged the Energi so that the Focus could charge overnight. This morning when I checked on the Energi its SOC was 97%. When my wife left for work she plugged in the Energi and it finished charging. When I left for work with it the ETE showed 7.144 kWh and the HVB temp was 64.4 F. Has anyone else seen such a change in the SOC displayed on the dash and reported by MFM as the battery has changed temp?

[larryh]

The Battery Management Systems cannot accurately compute SOC and energy in the HVB.  It is only an estimate.  Both depend are a function of battery temperature.  You loose 0.5 kWh of capacity when HVB temperature falls to 40 F. 

[Hybridbear]

The Battery Management Systems cannot accurately compute SOC and energy in the HVB.  It is only an estimate.  Both depend are a function of battery temperature.  You loose 0.5 kWh of capacity when HVB temperature falls to 40 F. 

So in this case I appear to have gained about 0.5 kWh in ETE when the temp rose from 40 F to 64 F.

[Hybridbear]

Last night when I got home the battery temp was around 50. Since we were planning to plug in the Focus overnight I told the Energi to charge immediately. When my wife got home from work & unplugged the Energi to plug in the Focus the Energi showed 85% SOC. This morning it showed 96% SOC. The battery temp is now 68.0.

Edited April 7, 2015 at 07:02 PM by Hybridbear

[lonzo71]

yep, the temp is on the rise!

[rbort]

Of course, I see this all the time with mine.  The SOC can rise or drop from day to day depending on the HVB temperature.  If the temp goes up, then the HVB SOC goes up, if it goes down then it goes down as well, I've seen a difference of about 10% reported in the HVB SOC.

 

This doesn't mean that your battery is charged more (from 85 to 96% reported), the HVB voltage rises or drops due to temp changes and that's what confuses the BMS.  

 

-=>Raja.

Edited April 7, 2015 at 04:30 PM by rbort

[larryh]

The HVB energy varies with temperature--see post 127.  The BMS takes temperature into account, along with many other factors, to determine the energy in the HVB.  SOC is computed as the current amount of energy in the HVB divided by the maximum energy that the HVB can store.   The BMS can only estimate the current energy and the maximum energy that can be stored in the HVB.  There is probably a 5% margin of error.  As temperature changes, its going to come up with different estimates for the current and maximum energy, so the SOC is going to change. 

 

I have plotted HVB voltage vs. SOC vs temperature.  I see no evidence that voltage varies with temperature at a given SOC.  WIth increasing temperature, the HVB voltage increases as well as the energy in the HVB.  The BMS takes this into account when computing SOC. 

Edited April 7, 2015 at 10:07 PM by larryh

[larryh]

I have now had my 2013 FFE for two years and driven 23,000 miles.  Looking through the data I have collected over this time, my best estimate of the SOH of the HVB is 96-97%.  When new, the HVB should store 7.2 kWh of energy at 100% SOC.  Lately, with the warming temperatures, mine stores about 6.95 kWh of energy.  For my 60 mile commutes, I have been averaging 5.5 kWh of energy from the HVB until the ICE turns on.  With the current outside temperatures, I would have expected about 5.7 kWh when new.  The most plug-in energy I have ever output from the HVB was 6.0 kWh (the outside temperature would have to be warmer to do that).  So degradation appears to be around 2% per year so far. 

Edited April 18, 2015 at 09:28 PM by larryh

[expresspotato]

Yeah the protections ford put into the battery seem to be fantastic... Probably has a lot to do with the variable draw allow from the battery. Less then low, less when cold, more we really full, more as the battery warms up.

 

My now 2013 FFH would probably give me about 1/3rd of a bar on Empower or just start the ice anyways after being frozen solid in -20C for 8+ hours.

Edited May 2, 2015 at 05:15 PM by expresspotato

[larryh]

The following chart plots HVB SOC vs. voltage.  The SOC seems to depend only on HVB voltage and nothing else.  HVB temperature and degradation of the HVB do not seem to influence SOC.  The measurements were made prior to and after completing trips when little power is drawn from the HVB.  While driving, the voltage will fluctuate greatly with the power drawn from the HVB.

 

To make this plot correctly, I would need to wait for the chemical reactions in the HVB to achieve equilibrium.  Until equilibrium is achieved, the voltage of the HVB will change.  That means I should let the HVB rest for a few hours before making measurements.  That is obviously not the case when I take measurements at the end of a trip.  As a consequence, the markers do not all fall on a straight line.  In particular, between 310 and 320 volts, their appear to be two lines of markers.  The top line is the measurements made when I arrive at work and the lower line is the measurements I make when I leave work.  Between the time I arrive and leave, the voltage may change until chemical reactions reach equilibrium. 

 

 

Edited June 6, 2015 at 03:07 AM by larryh

[larryh]

As an example how the HVB state changes between the time I arrive at work and the time I leave, consider a commute in the winter time.  When I arrived at work, the voltage was 311.13 V and SOC was 62.02%.  When I left work about 9 hours later, the voltage had risen to 311.8 V and the SOC had fallen to 55.18%. 

 

The BECM cannot accurately measure the HVB voltage while driving since the voltage fluctuates greatly with power.  So instead, it has the monitor the amount of energy drawn from the HVB.   It keeps an estimate of the amount of energy remaining in the HVB at all times (known as Energy to Empty or ETE).   That morning ETE was 6.44 kWh when I started to work and 4.14 kWh when I arrived.  That means the car consumed 6.44 - 4.14 = 2.30 kWh of energy from the HVB as measured by the car. 

 

The SOC at the start of the trip was 96.54%.  At 100% SOC, ETE would be 6.44 kWh/0.9654 = 6.67 kWh.  SOC is simply the fraction of the original 6.67 kWh of energy remaining the HVB.  When I arrive to work, ETE is 4.14 kWh and thus the car estimates the HVB SOC to be 4.14/6.67 = 62.02%, which was the value reported by the car.

 

The car now sits for 9 hours and gives the HVB time to rest.  When I begin my commute home, the car can read the true equilibrium HVB voltage, which is 311.8 Volts.  From the curve in the chart above, it then determines that SOC is 55.18%.  It couldn't use this chart when I arrived at work because it could not measure the equilibrium voltage of the HVB.  It takes time for chemical reactions to reach equilibrium.  Thus I see the SOC jump from 62.02% when I arrived at work to 55.18% when I left work. 

 

The car simply did not compute the correct ETE at the start of the trip.  That is impossible to do.  You cannot know the amount of energy that the HVB will provide until after the fact.  The amount of energy that the HVB provides depends on how much power you draw from the HVB.  If you draw more power, you get less energy out of the battery. 

 

Sometimes the HVB voltage rises, sometimes if falls, and sometimes it remains the same from the time I arrive to work to the time I leave.  In any case, only after the battery has rested a while can the above chart be used to determine SOC.  Otherwise, it has to estimate SOC based on estimated ETE, which may be inaccurate. 

Edited June 6, 2015 at 03:18 AM by larryh

[larryh]

As another example, when I arrived home today, the HVB voltage was 290.45 V and SOC was 14.96% (which is estimated based on an ETE of 1.06 kWh).  If you look at the plot above, 14.96% SOC is about 5% above the solid black line at 290.45 V.  The car cannot measure the true equilibrium voltage of the HVB until the HVB has rested a while.  The measured 290.45 V is not the equilibrium voltage and hence one cannot simply look up the SOC based on the chart above.  We are forced to estimate the SOC based on ETE as described in the previous post. 

 

One hour later, after the HVB has rested, we can now measure the voltage of the HVB and use the chart above.  One hour later, the voltage is measured to be 291.42 Volts.  Based on the chart above, that corresponds to a SOC of 9.85%, which is what the car reports.  Based on the actual SOC of 9.85%, the car then revises the current ETE estimate from 1.06 kWh to 0.7 kWh. The energy in the HVB is rather low.  It should not be left in such a low state for very long. 

Edited June 6, 2015 at 03:45 AM by larryh