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Guest Message by DevFuse

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HVB Health from OBDII Data Analysis

HVB HV Battery Health OBDII Resistance

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#1 OFFLINE   SnowStorm

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Posted 03 March 2015 - 08:13 PM

With detailed data from OBDII (see this post) I've started thinking about ways to track the health of our HV batteries.  But first, some of the data available from the Battery Energy Control Module (BECM) is:

  • Battery Age:  Mine is 23 months - sounds right for car built in April 2013.
  • Battery voltage:  Runs about 282V.  A 5 minute run gave min/max of 264V/303V.
  • Battery Current:  Varied from -114 amps (charge) to 94 amps (discharge).  Limits (see below) should be about +/-120 amps.
  • Battery Temperature:  My 5 minute run had values from 62 to 66F (mid 30s OAT).
  • State of Charge (SOC):  Both actual and displayed values in %.  Fitting a straight line to the data gives:   Actual SOC = 0.38545*(Displayed SOC) + 26.4%
  • Charge Limit:  Reads a constant 35000 watts.  At 282 volts that's 124 amps.
  • Average Cell Voltage:  My min/average/max for this PID was 3.48/3.71/3.99 volts
  • Minimum Cell Voltage:  My min/average/max for this PID was 3.44/3.70/3.97 volts
  • Battery Cell Variation:  My min/average/max for this PID was 0.00/0.02/0.07 volts.  On a statistical basis the % of times each value was registered was:
    0.00=0.3%  0.01=58.8%  0.02=24.3%  0.03=10.1%  0.04=6.0%  0.05=0.4%  0.06=0.1%  0.07=0.02% (only once!)
  • SOC Module Variation:  Reads a constant 1.62% - not sure what this means.  Will it go up?
  • In Car Temp:  Mine read 52 or 54 F the whole time (we Virginians are tough!).  Of course this is probably the inlet cooling air, so with 30s outside and recirc heat likely on up front, the air reaching the battery could well be that cool (but then we don't sound so tough).
  • Fan Speed:  Read 0 during this run - I guess the HVB wasn't warm enough.

So back to health, here are some possibilities.

  1. Battery Cell Variation: With age, this might go up.  Right now I have a maximum of 0.07 volts.  You must be careful though because the maximum values appear to depend on the maximum current.  Will try and set up a "standardized" test where the battery is run through heavy charge/discharge cycles of, say, +/-100 to 120 amps.
  2. Battery Cell Average & Minimum Voltage:  Might be useful but the above "variation" may be enough of an indicator.
  3. Battery Resistance:  This value must be calculated.  Using the average pack voltage, voltage variation with charge/discharge and battery current, the resistance of my battery appears to be about 0.10 to 0.15 ohms.  Again the above test should give a more consistent value.  Resistance may vary with SOC and temperature and is expected (?) to go up with time.
  4. Battery Age:  For reference
  5. Total Miles:  For reference (and maybe lifetime EV miles as well)

Sure wish I had numbers from when The Enterprise was new - and from other cars out there!


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#2 OFFLINE   SStoner

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Posted 03 March 2015 - 10:46 PM

DrD had posted a picture on the NRG forum.  I don't where I saw it. It was there somewhere ;)



#3 OFFLINE   SPL Tech

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Posted 08 March 2015 - 04:25 PM

Interesting. However, according to Ford the electric motor is 88kW, which would 290 amps, or almost triple what you said the limit is. On the other hand, 88kW seems really off. 88kW is nearly 120 HP, and the hybrid is only rated for 141 HP. I am going to go ahead and guess the ICE can put out more than ~20 HP. The numbers are not adding up here.


Edited by SPL Tech, 08 March 2015 - 04:27 PM.


#4 OFFLINE   SPL Tech

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Posted 08 March 2015 - 04:26 PM

"

Electric Engine Specifications   Electric Motor Specifications (C-MAX Hybrid)  Motor type 88kW Permanent Magnet AC Synchronous Motor 

http://www.ford.com/...cations/engine/


Edited by SPL Tech, 08 March 2015 - 04:26 PM.


#5 OFFLINE   SnowStorm

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Posted 08 March 2015 - 10:59 PM

Interesting. However, according to Ford the electric motor is 88kW, which would 290 amps, or almost triple what you said the limit is. On the other hand, 88kW seems really off. 88kW is nearly 120 HP, and the hybrid is only rated for 141 HP. I am going to go ahead and guess the ICE can put out more than ~20 HP. The numbers are not adding up here.

Marketing numbers usually don't add up!  Actually, I believe the motor is good for 88kW but the battery and/or inverter are not.  The NRG with its bigger battery but same motor has a slightly higher total at 195hp.  Perhaps Ford is planning a future model with more power but the same transmission.  I suspect its easier to test/qualify a new battery than a new transmission.  I have logged more data and, sure enough, there are no charge or discharge peaks beyond about 34,700 watts.



#6 OFFLINE   hybridbear

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Posted 09 March 2015 - 10:57 AM

Interesting. However, according to Ford the electric motor is 88kW, which would 290 amps, or almost triple what you said the limit is. On the other hand, 88kW seems really off. 88kW is nearly 120 HP, and the hybrid is only rated for 141 HP. I am going to go ahead and guess the ICE can put out more than ~20 HP. The numbers are not adding up here.

The electric motor is 88 kW but the max discharge is usually 35 kW in the hybrid and 65 kW in the Energi. The ICE is rated at 141 HP by itself. The combined output of the hybrid is 188 HP and the combined Energi HP is 195.

 

I have seen the ICE put out as much as 60-65 kW when climbing the mountains. I've seen the electric motor put out 50 kW in our Energi.


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#7 OFFLINE   fbov

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Posted 09 March 2015 - 04:22 PM

.... The numbers are not adding up here.

That's because you're adding peak values that can never co-exist at any given time.

 

An ICE has a rising torque curve, an electric motor a falling curve with RPM. That makes them complementary - one makes power in the RPM range where the other doesn't. I can't find a good explanation for the rest of it, though.

 

HAve fun,

Frank



#8 OFFLINE   SnowStorm

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Posted 09 March 2015 - 08:19 PM

Well, actually, the numbers do add up.  141hp + 35kW/0.746kW/hp = 141 + 47 = 188hp just like Ford says.  I would think that the battery/inverter/motor combination can do 35kW at any speed above, who knows, maybe 45 mph.  So, once the ICE is at its peak of 141hp there should be no problem having the full 35kW electric.  (Of course that is ignoring the slight power losses in the inverter and motor.)  As a cross check one could always floor it :shift:, measure the acceleration, take the weight of the car and calculate the force and then the power at the given speed.  ("This calculation is left as an exercise for the reader"! :thumbsup: )


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#9 OFFLINE   SnowStorm

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Posted 25 March 2015 - 04:01 PM

More observations of OBDII battery data show:

  1. Maximum charging current from ICE is about 35 amps.
  2. Maximum charging current while "coasting" (foot off accelerator) is also about 35 amps - even down hill.

Moderate regen braking or hard acceleration will send the charge/discharge current past 100 amps easily.  So for maximum battery life we should avoid "flooring it" :cry: and "coast" as long as possible before braking :) .  (You can get nearly 100% brake scores and be hitting 100+ amps every stop.)  How significant is high current to shortened life?  Without data we can only debate (but I still plan to floor it once in a while!) :shift:


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#10 OFFLINE   fbov

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Posted 26 March 2015 - 04:58 PM

From my spec sheet 

PERFORMANCE

Engine horsepower 141 hp

Engine torque 129 lb.-ft.

 

and

ELECTRIC MOTOR/GENERATOR

Type Permanent magnet AC synchronous motor

Output 118 hp@6,000 RPM/88kW@6,000

Torque 177 lb.-ft./240Nm

 

so I can see where folks fail to notice

HIGH VOLTAGE BATTERY

Type 1.4 kWh Lithium-ion

Peak power (charge sustain mode) 35 kW (emphasis added)

 

which jives with your numbers, for sustainable power.

 

What doesn't jive is:

141HP from the engine + 118HP from the motor >> Total system power (sustain) 188 hp

unless you realize that the 118HP from the "electric motor/generator" includes a unit that's not connected to the drivetrain, and can't move the car directly.

 

Have fun,

Frank



#11 OFFLINE   SnowStorm

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Posted 26 March 2015 - 09:54 PM

The motor itself might be capable of 118 HP if you had a big enough power source but the hybrid battery can only do 35kW (47 HP) and the Enerrgi battery 65 kW (87 HP).  (You know - chain is only as strong as its weakest link.)  So the hybrid has 188 total HP (141+47).  The Energi can apparently do 87 HP in EV mode but, for some unknown reason, is limited to a total of 195 (not 141+87=228 HP).

 

Note that the 35 amps I mentioned above is only about 10 kW.  Flooring it will pull 135 amps (I've seen it) which gives 35 kW at 260 volts from the HVB.  My point is that the car seems to limit HVB current to 35 amps (10 kW of power) as much as possible.

 

BTW, the "kW" bar graph looks to be 10 kW per line - I was able to check the first two.


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#12 OFFLINE   SPL Tech

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Posted 27 March 2015 - 12:08 AM

 

 

  1. Maximum charging current while "coasting" (foot off accelerator) is also about 35 amps - even down hill.

) :shift:

That seems like such a waste. That's nearly 10,000W, which is about 15hp. So 15hp is being wasted just to charge the battery and then go back into the drivetrain again. I think that when driving at high speed the car should stop charging the battery altogether once it reaches about 75%. Otherwise you have this really wasteful cycle of charging the battery, then depleting it right away, then just charging it again, and over and over all along the entire freeway. That doesent make sense, especially if the load to charge the HV is 15hp which is quite significant. Just cut off the HV charge and run 100% on ICE until you go downhill and the engine shuts off or you go up hill and need more power.

 

Edit: I disagree that the charge is 35A though while costing. I'll have to look into FORscan tomorrow again, but I recall it being more like 4A, quite low. If it was 35A of drag on the wheels, which is 15HP ignoring MG2 losses, as soon as you let off the gas you would notice an instant drag. 15 HP is very noticeable.


Edited by SPL Tech, 27 March 2015 - 12:10 AM.

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#13 OFFLINE   fbov

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Posted 30 March 2015 - 10:52 AM

The motor itself might be capable of 118 HP if you had a big enough power source but the hybrid battery can only do 35kW (47 HP) and the Enerrgi battery 65 kW (87 HP).  (You know - chain is only as strong as its weakest link.)  So the hybrid has 188 total HP (141+47).  The Energi can apparently do 87 HP in EV mode but, for some unknown reason, is limited to a total of 195 (not 141+87=228 HP).

Two thoughts...

 

It might just be marketing... add tractor and charger capacities to get 118HP, even if only one is a motor/generator that can actually drive the wheels

 

There may be times when it's advantageous for the ICE to generate added current for the tractor MG, beyond what the battery can provide. This car is darn quick for a 1.8L intake-displacement engine pushing 2 tons...

 

HAve fun,

Frank



#14 OFFLINE   vitalic

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Posted 10 April 2015 - 12:21 AM

I found very interesting info about HV battery http://energy.gov/si...ryC-Max8698.pdf


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#15 OFFLINE   Plus 3 Golfer

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Posted 10 April 2015 - 06:48 AM

Good info especially the average capacity which at 4118 miles is 1390 Wh or 1.39 kWh.  It will be interesting to follow as mileage accumulates.  Here's a link to all testing documents of the C-Max Hybrid. It appears the 4 test vehicles have significantly more mileage on them then in the battery test docs.  I hope they eventually update the battery test docs.


Edited by Plus 3 Golfer, 10 April 2015 - 07:40 AM.

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#16 OFFLINE   SnowStorm

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Posted 10 April 2015 - 10:07 PM

Great info - thanks for the links!  Some thoughts:

  1. Wonder what kind of fleet driving it is - 37 mpg - most of us do a lot better.  Maybe not too bad for a :noobie: ???
  2. Love the data for mpg versus speed (did they use E0 gas?).  Says I should get 56.7 mpg at 55 mph.  I get about 53 or so.  Maybe they used grill shutters!
    Also shows you could do 1000 miles per tank (13.5 gal) if you putter along at 40 mph!  Anyone up for a 25 hour drive? :drop:
  3. Max speed of 117 mph! :arrive_alive: (and 100 miles per tank?)
  4. Can we really do 22.7 mph (All Electric) up a 25% grade?  That's pretty steep.
  5. Then look at that urban cycle - 60.4 mpg at 72F versus 28.9 mpg at 20F (cold start)!
    Come on now - no more short trips in winter! :nonono:
  6. Peak power into battery (braking) of only 0.62kW?  Doesn't make sense.  It can go to 35 kW.  Bet they got a lousy score!
  7. Peak power coasting of 10 kW - that's consistent with what I've seen.
  8. Have these cars had the mileage "upgrade" from Aug 2014?  Everyone seemed to think the battery was being worked harder after that time.
  9. Battery resistance about 0.23 ohms.  I guess my crude measurement of 0.10 to 0.15 ohms from OBDII data was at least in the ballpark - sort of.

Absolutely wonderful data.  In the end I bet it will show that the battery will last 100s of thousands of miles without enough degradation to really matter in a hybrid.  Can't wait for the next data set to arrive.


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#17 OFFLINE   SPL Tech

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Posted 10 April 2015 - 10:47 PM

 

  1. Peak power into battery (braking) of only 0.62kW?  Doesn't make sense.  It can go to 35 kW.  Bet they got a lousy score!

They were testing the minimum stopping distance from 60-0 which means they slammed the brake peddle. In emergency braking I am sure the regen cycle stays off and the vehicle only uses the brake calipers. That would make the most sense as it would be the most stable for extreme braking.



#18 OFFLINE   vitalic

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Posted 13 April 2015 - 11:59 AM

There is no sense to do not use regen even in emergency stop. Regen will give one more force which will help to stop vehicle. So with regen you will stop more quick and use less distance than without.



#19 OFFLINE   Plus 3 Golfer

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Posted 13 April 2015 - 04:56 PM

Great info - thanks for the links!  Some thoughts:

  1. Wonder what kind of fleet driving it is - 37 mpg - most of us do a lot better.  Maybe not too bad for a :noobie: ???
  2. Love the data for mpg versus speed (did they use E0 gas?).  Says I should get 56.7 mpg at 55 mph.  I get about 53 or so.  Maybe they used grill shutters!
    Also shows you could do 1000 miles per tank (13.5 gal) if you putter along at 40 mph!  Anyone up for a 25 hour drive? :drop:
  3. Max speed of 117 mph! :arrive_alive: (and 100 miles per tank?)
  4. Can we really do 22.7 mph (All Electric) up a 25% grade?  That's pretty steep.
  5. Then look at that urban cycle - 60.4 mpg at 72F versus 28.9 mpg at 20F (cold start)!
    Come on now - no more short trips in winter! :nonono:
  6. Peak power into battery (braking) of only 0.62kW?  Doesn't make sense.  It can go to 35 kW.  Bet they got a lousy score!
  7. Peak power coasting of 10 kW - that's consistent with what I've seen.
  8. Have these cars had the mileage "upgrade" from Aug 2014?  Everyone seemed to think the battery was being worked harder after that time.
  9. Battery resistance about 0.23 ohms.  I guess my crude measurement of 0.10 to 0.15 ohms from OBDII data was at least in the ballpark - sort of.

Absolutely wonderful data.  In the end I bet it will show that the battery will last 100s of thousands of miles without enough degradation to really matter in a hybrid.  Can't wait for the next data set to arrive.

ANY DATA DERIVED FROM THE DYNAMOMETER TESTING IS FLAWED.

 

I covered this in another tread.  The dyno coefficients in footnote 9 are incorrect.  Here's the link showing the correct coefficients (used in 2014 Ford EPA FE update) and the incorrect coefficients (used in Aug. 2013 EPA FE update).  Note the difference in RLHP using the latest coefficients.

 

Footnote 9:

Dynamometer testing occurs after the track testing is complete. Dynamometer testing began on August 23, 2013, with the vehicle odometer reading 4,451 miles. A comprehensive explanation of the dynamometer facility and methodology can be found at http://www.transportation.anl.gov/D3/, titled “Chassis Dynamometer Testing Reference Document”. The ABC coefficients derived from track coastdown testing and matched on the dynamometer were A: 21.75 lb, B: 0.365 lb/mph, and C: 0.01859 lb/mph2 .

 


Edited by Plus 3 Golfer, 13 April 2015 - 07:13 PM.


#20 OFFLINE   fbov

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Posted 14 April 2015 - 12:15 PM

There is no sense to do not use regen even in emergency stop. Regen will give one more force which will help to stop vehicle. So with regen you will stop more quick and use less distance than without.

In an emergency stop, the most critical thing is maintaining control, thus ABS systems.

 

Given you can already lock the front brakes, there's nothing to be gained. There is some advantage to using only hydraulic brakes under sensor-driven control in a panic stop situation. Try downshifting a FWD standard tranny on a slippery road. You'll find that proper rear wheel braking is critical to vehicle stability.

 

Have fun,

Frank








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