HVB Health from OBDII Data Analysis

[SnowStorm]

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!

[SStoner]

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

[SPL Tech]

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 March 8, 2015 by SPL Tech

[SPL Tech]

"

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

http://www.ford.com/cars/cmax/2014/specifications/engine/

Edited March 8, 2015 by SPL Tech

[SnowStorm]

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.

[hybridbear]

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.

[fbov]

.... 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

[SnowStorm]

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: )

[SnowStorm]

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:

[fbov]

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

[SnowStorm]

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.

[SPL Tech]

 

 

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 March 27, 2015 by SPL Tech

[fbov]

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

[vitalic]

I found very interesting info about HV battery http://energy.gov/sites/prod/files/2015/02/f19/batteryC-Max8698.pdf

[plus 3 golfer]

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 April 10, 2015 by Plus 3 Golfer

[SnowStorm]

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.

[SPL Tech]

 

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.

[vitalic]

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.

[plus 3 golfer]

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 April 14, 2015 by Plus 3 Golfer

[fbov]

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

[SnowStorm]

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.

Of course.  Locked wheels (if no ABS) gives no regen!  And with ABS pulsing away, controlling the electrical regen process could be a challenge.  On top of that, regen is limited to 35 kW which, even if it could be achieved for the entire 3 second stop, would only get you about 30 watt-hours of energy and a braking score of maybe 18%!  Not worth loosing sleep over. :sandman:

Edited April 15, 2015 by SnowStorm

[Noah Harbinger]

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.

 

I suspect what you're missing is that traction / generator motor set function as, effectively, the 'gear ratio' portion of the transmission.

 

For example, suppose you're at a dead stop, and you mash the pedal (and supposing a low enough SOC that the car does not draw from the HV battery). The annular ring will be still, allowing/forcing torque from the ICE to *entirely* drives the generator motor; and the power generated there drives the traction motor, effectively providing an infinite gear ratio - but constrained up to the 64kW generator motor's capacity. 

 

With charge, you can get another boost of up to 22kW from the HV system, to hit the 88kW limit on the traction motor. 

 

In more general concept, the degree to which the generator motor resists the turning of the engine translates to what proportion of the engine's torque is sent directly to the wheels. The "resistance" torque applied by the generator, generates electricity, which may go to either the traction motor (if whether the 'commanded power' is greater than what the engine supplies), or to charge the battery.

 

The greater rating for the Energi is probably because its battery can supply more power. 

Edited April 22, 2015 by Noah Harbinger

[hybridbear]

I suspect what you're missing is that traction / generator motor set function as, effectively, the 'gear ratio' portion of the transmission.

 

For example, suppose you're at a dead stop, and you mash the pedal (and supposing a low enough SOC that the car does not draw from the HV battery). The annular ring will be still, allowing/forcing torque from the ICE to *entirely* drives the generator motor; and the power generated there drives the traction motor, effectively providing an infinite gear ratio - but constrained up to the 64kW generator motor's capacity. 

 

With charge, you can get another boost of up to 22kW from the HV system, to hit the 88kW limit on the traction motor. 

 

In more general concept, the degree to which the generator motor resists the turning of the engine translates to what proportion of the engine's torque is sent directly to the wheels. The "resistance" torque applied by the generator, generates electricity, which may go to either the traction motor (if whether the 'commanded power' is greater than what the engine supplies), or to charge the battery.

 

The greater rating for the Energi is probably because its battery can supply more power. 

The hybrid has a maximum charge/discharge limit for the HVB of 35 kW under ideal conditions. When the HVB is very cold or very hot this number will be reduced. Thus the maximum power for acceleration or deceleration in EV mode is 35 kW. The Energi has a 35 kW maximum charge limit but a higher maximum discharge limit. I've seen the max discharge limit as high as 68 kW with a fully charged HVB. As the HVB SOC falls the max discharge limit drops as well. If your HVB is nearly depleted it drops to around 50-55 kW. Once the car goes into hybrid mode with a depleted battery the max discharge limit is usually 35 kW, just like in the hybrid.

[vitalic]

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

Are you forgot that regen force depends of rpm? Higher rpm - higher regen force, lower rpm - lower regen force, 0 rpm - 0 regen force. So it's hard to block wheels by regen force. And it's easy to check if c-max uses regen in emergency stop - just monitor  is there charging impulse in emergency stop or not. I am 90% sure you will find charging impulse.

Edited April 22, 2015 by vitalic

[plus 3 golfer]

Are you forgot that regen force depends of rpm? Higher rpm - higher regen force, lower rpm - lower regen force, 0 rpm - 0 regen force. So it's hard to block wheels by regen force. And it's easy to check if c-max uses regen in emergency stop - just monitor  is there charging impulse in emergency stop or not. I am 90% sure you will find charging impulse.

fotomoto tried to see what the lowest  brake score return % he could get. Even with ABS activation, he achieved 9%.  So, it appears that there is always regenerative braking (unless the HVB is full).