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Regen When Driving in EV


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33 replies to this topic

#21 OFFLINE   larryh

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Posted 26 April 2014 - 05:53 AM

I tried a simple experiment this morning.  Starting from the same stopping point going about 55 mph before the stop sign, I tried two different methods to stop. 

 

- Lifting my foot off the accelerator with the car in Drive about 0.4 miles before the stop sign then using the brake as I approached the stop sign.   Regen occurred slowly over a long period of time. 

 

- Shifting the car into neutral until I got closer to the stop sign (to stop consuming/adding energy from/to the HVB), then shifting into Low to brake, and then shifting back to neutral, and eventually back to drive and applying the brake.  Regen occurred rapidly over a short period of time.

 

With the slow regen method, the motor/generator produced 0.0761 kWh of electricity.  With the fast regen method, the motor/generator produced 0.0896 kWh of electricity.   For fast regen method, the motor/generator produced 18% more electricity.  This takes into account the power used by the car's accessories.

 

With the slow regen method, the car claims that 0.062 kWh of energy was added to the HVB.  With the fast regen method, the car claims that 0.078 kWh of energy was added.  However, the slow regen method took much longer than the fast regen method.  The car's accessories used twice as much energy during the slow regen method than the fast regen method.  Taking that into account, the fast regen method added 19% more energy to the HVB. 

 

So it appears to make a difference in the amount of regen for slow vs. faster braking.  You can get about 18-19% more regen with faster braking if you do it right.  However, if you continue to press the accelerator to maintain the car's momentum until the last possible moment, and then brake at the maximum charge limit, you probably won't realize much, if any, of the 18-19% additional regen.  It may be wiped out by the additional time you were using energy by applying the accelerator. 

 

Note that you don't want to apply the brakes when the car is in neutral.  You will get no regen from the brakes driving in neutral.

 

One would have to experiment a lot more to determine the optimal braking strategy for various situations. 


Edited by larryh, 26 April 2014 - 05:59 AM.








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#22 OFFLINE   timwil56

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Posted 26 April 2014 - 06:16 AM

I want to maximize regeneration, but .016kWh of energy gained between slow and fast regen isn't worth all the steps to get it, at least for me. What works for you, may not work for me and I just believe it is unsafe to be moving in neutral, regardless of the speed or circumstances. This topic turned into quite the discussion, with a lot of good information shared. Thanks to all who contributed.



#23 OFFLINE   larryh

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Posted 26 April 2014 - 06:58 AM

I do not think it is worth all the trouble either.  I normally just leave the car in drive and brake normally, trying to get 100% regen.  But different braking techniques do have an impact on regen.  This was the first tried I tried this, simply as an experiment.


Edited by larryh, 26 April 2014 - 07:05 AM.


#24 OFFLINE   GaryG

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Posted 26 April 2014 - 08:38 AM

Thanks Larry, and I agree with your reply. I thought when you were saying hard braking first, you meant getting into the friction brakes.

 

Here is how I brake:

 

Most of the time I'm in an N glide after P&G and waiting for the need to brake with L or shift back to D for a pulse again. I estimate the stopping distance for a stop sign or a changing stoplight. I simply shift to L first for all my stopping and try to time my stop using the brake pedal for the final stop. I will coast in N if I see a change in a stoplight to green and time traffic so I match the speed of the traffic accelerating. It's back to P&G as traffic accelerates ahead.

 

In short, I use L for all my stopping first, and use the brake pedal as light as I can in addition if I need to stop quicker. From my range photos of 33.9 and 39.6 miles, I got a 100% score and a 99% score. On the 99% score, someone pulled out in front of me and I had no choice but to use the fiction brakes or hit them. That pisses me off, but I only had two choices? I have a lifetime of 98% braking score, but my wife drives my Energi also.

 

Gary



#25 OFFLINE   rbort

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Posted 26 April 2014 - 05:48 PM

Larry. try this experiment for me.

 

What I do is if I'm driving and the light turns yellow in the distance, I stop pressing on the gas and coast in D.  When I get closer to the light, I shift it into L and let the car slow down.  I time the shift into L with the speed I have and the distance to go so once the car slows down completely I just have to hold the brake from less than 10mph to come to a stop.  If someone is behind me I pad the shifting to L with the lightest brake pressure that will show regeneration going on to light up the brake lights.

 

If I have to stop quick (light turned suddenly) then I shift to L and drag it out as much as possible with the brake pedal so I'm at or just past the stop line.  I may have to brake harder due to the short stopping distance but I try to drag it out longer to give a chance to get 100% brake score.

 

Can you test the glide in D and then braking with L for me and see how it works?

 

If the speed is too slow or I got alot of distance to cover, then I never go into L and just use light braking as necessary to get there without using any more "gas".

 

For what its worth, I don't glide in N or pulse and glide, just set the cruise to 35-40mph sit back, relax, and talk on the phone as I purr along.  The way I see if, if there is enough battery to get there, who cares, burn a little more and relax rather than get that speed up / N / slow down ride the whole way.  After all, electricity is free.

 

-=>Raja.


Edited by rbort, 26 April 2014 - 05:52 PM.


#26 OFFLINE   larryh

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Posted 27 April 2014 - 04:05 AM

I have created charts showing the efficiency of the motor/generator when propelling the vehicle and during regen:

 

Propulsion:  "http://www.fordfusio...or-ice/?p=13034"

Regen:        "http://www.fordfusio...or-ice/?p=13186"

 

I think the charts are reasonably accurate.

 

If you want to maximize efficiency, you want to avoid coasting in Drive where regen efficiency is less than 75%.  If you use Low to brake, regen efficiency will be 95% or better.  When supplying power to the motor/generator, you get much better efficiency when you supply 40 kW of power (90%+ efficiency) vs. 5 kW of power (55% efficiency at 55 mph). 

 

You want to operate in the regions of maximum efficiency as much as possible.  The three regions you want to be in are:

1.  Shift set to Drive applying lots of power to the motor/generator, i.e. accelerating.

2.  Shift set to Low receiving lots of regen from the motor/generator, i.e. braking. 

3.  Shift set to Neutral when the electrical connection between the motor/generator and HVB is disconnected.  Otherwise, you are forced to operate in an inefficient region wasting energy.   Since the HVB is disconnected, you won't get any regen if you apply the brakes in neutral.  So you have to shift to Low or Drive when you apply the brakes.  But I am not sure that it is legal to drive in neutral in any case (I think it only applies to steep downgrades where you would want to use hill assist instead).

 

You also have to take into account rolling resistance, aerodynamic drag, and the internal friction of the car's transmission components.  They consume a significant amount of energy.  To reduce this loss, your only choice is to drive slower (within reason).

 

In the regen example I previously posted, the kinetic energy of the car at 54 mph was about 0.148 kWh.  The motor/generator only recovered 60% of the kinetic energy.  But that was not a very efficient stop either--I was constrained to use 0.4 miles to stop for a fair comparison to the slow regen method.  I think you can get it close to 80%.

 

It will require a lot of skill to optimize driving to make efficient use of this knowledge. I have no experience in this domain, so I am not the right person to ask. 

 

It might also help to understand how the eCVT works in the car.  I have several rather technical postings about it starting around here (you might find other items of interest before that posting in the thread):

 

"http://www.fordfusio...or-ice/?p=13310"


Edited by larryh, 27 April 2014 - 05:55 AM.

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#27 OFFLINE   GaryG

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Posted 27 April 2014 - 03:24 PM

Larry. try this experiment for me.

 

What I do is if I'm driving and the light turns yellow in the distance, I stop pressing on the gas and coast in D.  When I get closer to the light, I shift it into L and let the car slow down.  I time the shift into L with the speed I have and the distance to go so once the car slows down completely I just have to hold the brake from less than 10mph to come to a stop.  If someone is behind me I pad the shifting to L with the lightest brake pressure that will show regeneration going on to light up the brake lights.

 

If I have to stop quick (light turned suddenly) then I shift to L and drag it out as much as possible with the brake pedal so I'm at or just past the stop line.  I may have to brake harder due to the short stopping distance but I try to drag it out longer to give a chance to get 100% brake score.

 

Can you test the glide in D and then braking with L for me and see how it works?

 

If the speed is too slow or I got alot of distance to cover, then I never go into L and just use light braking as necessary to get there without using any more "gas".

 

For what its worth, I don't glide in N or pulse and glide, just set the cruise to 35-40mph sit back, relax, and talk on the phone as I purr along.  The way I see if, if there is enough battery to get there, who cares, burn a little more and relax rather than get that speed up / N / slow down ride the whole way.  After all, electricity is free.

 

-=>Raja.

 

Several years ago, I had other hypermilers come down on me for stating Sync allowed me to talk on the phone while driving in my '09 FEH. I had noticed many bad drivers driving much slower, changing lanes improperly and just about causing accidents in front of me. Almost all had a cellphone to their ear when I got around them. I thought it was okay to use the hands free Sync and talk on the phone and I was dead wrong. My hypermiler friends told me to never talk on the phone while driving, or at least answer a call with I'll call you right back when I come to a stop.

 

I did my own test and found they were right. When I'm hypermiling, I have all these techniques I use during a segment like not allowing the battery to get out of some parameters, and accelerating at a certain RPM etc. I found when I got off the phone while hypermiling, MPG was off and I didn't remember letting things get out of control. Then I remembered this has happened many times in the past when I was talking on the phone with my hands free Sync. 

 

It doesn't matter if you're hypermiling or not, you can't concentrate on both driving and talking on the phone. The problem is, most people will talk on the phone because this makes time fly while you're driving. Just like you said "sit back, relax, and talk on the phone as I purr along"

 

Gary   


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#28 OFFLINE   rbort

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Posted 27 April 2014 - 07:15 PM

You're right Gary, talking on the phone while driving does take up some brain waves and part of your processing is going towards the conversation. 

 

Hypermilling does require alot of effort and concentration, I did try this this evening but apparently I'm not very good at it as I did worse I think than just sitting on cruise and enjoying the ride.  I'll make a separate post right now.  

 

-=>Raja.



#29 OFFLINE   David A

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Posted 27 July 2018 - 03:46 PM

So when regenerating does the captured energy charge the larger partitioned part of the  HV battery or the smaller Hybrid partition?

Does it make a difference? The reason I ask is the MFM charge and trip and charge log tells me I drove 5.2 miles and used 1.9 kwh of electric charge and 1.3 miles were regenerated on that trip.  Does the 1.9 kwh include any energy charge created by regen or is that the total amont of electricity used and the rest is returned to the battery?

 

To make this obtuse question more clear: Did I use a total of 1.9 kwh or did I use 1.9 kwh more than was regenned on that trip?



#30 OFFLINE   David A

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Posted 27 July 2018 - 03:56 PM

Also: I understand charging with the 120 volt OEM cord there is some line loss or whatever. I have read, but do not know, that only about 75% of the wattage from the 120 OEM cord actually makes its way to the HV battery. So if the maximum charge rate with the OEM cord is 1.3 kwh, would the actual charge per hour into the battery be expressed as  1.3 X 1 hr X .75 equaling .975 kw charge per hour>

 

Im trying to figure out if my HV battery is compromised alerady at 7000 miles 

 

It only takes abut 4 3/4 to 5 hours to charge. Im trying to figure out if the battery has the capacity to store only 5 X 1.3 X .75 or 4.875 kwh?

 

Am I making sense? 



#31 OFFLINE   spirilis

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Posted 27 July 2018 - 04:11 PM

I think it means you used 1.9kwh more than all regen on that trip.

#32 OFFLINE   spirilis

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Posted 27 July 2018 - 04:12 PM

Also I think your math is right about the Level 1 120V charging. IIRC it's closer to 85% efficiency with 240V but I haven't studied 120V charging as much.

#33 OFFLINE   Levi Smith

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Posted 30 July 2018 - 06:59 AM

So when regenerating does the captured energy charge the larger partitioned part of the  HV battery or the smaller Hybrid partition?

Does it make a difference? The reason I ask is the MFM charge and trip and charge log tells me I drove 5.2 miles and used 1.9 kwh of electric charge and 1.3 miles were regenerated on that trip.  Does the 1.9 kwh include any energy charge created by regen or is that the total amont of electricity used and the rest is returned to the battery?

 

To make this obtuse question more clear: Did I use a total of 1.9 kwh or did I use 1.9 kwh more than was regenned on that trip?

 

The "partitions" as you call them are just different percentages of the total battery charge.  There's no actual partitions.  I don't recall the exact numbers but for ballpark ideas you can think that when the car is fully charged that your battery is at like 95% charged.  And when your EV mode runs out and you switch to Hybrid then your battery might be at around 20% and it will never go lower than like 10% even if hybrid mode shows empty.    So any time you charge the car whether via regen or with the cord, it's just increasing the % of the total battery charge.  So it will either show higher in EV mode if charging there, or higher in hybrid mode if charging at that time(or enough to bring it back up in to EV mode again).

 

I certainly wouldn't swear to which way the car reports things and from what I've heard there have been some changes over the years.

 

As I recall on my 2013, it seems like it shows KWH used but then regen drops the KWH used back down.  Like if I drove for 10 miles and used 2KWH, then went down a big hill and regen'd .5KWH the trip meter would read 1.5KWH.  



#34 OFFLINE   Levi Smith

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Posted 30 July 2018 - 07:25 AM

Also: I understand charging with the 120 volt OEM cord there is some line loss or whatever. I have read, but do not know, that only about 75% of the wattage from the 120 OEM cord actually makes its way to the HV battery. So if the maximum charge rate with the OEM cord is 1.3 kwh, would the actual charge per hour into the battery be expressed as  1.3 X 1 hr X .75 equaling .975 kw charge per hour>

 

Im trying to figure out if my HV battery is compromised alerady at 7000 miles 

 

It only takes abut 4 3/4 to 5 hours to charge. Im trying to figure out if the battery has the capacity to store only 5 X 1.3 X .75 or 4.875 kwh?

 

Am I making sense? 

 

Yeah, there are losses just because charging isn't 100% efficient in the first place and then there are the overhead losses.  Again, I don't know the exact numbers for the C-Max, but any time the car is "on"(including charging) the 12V side of things is powered up and powers computers, fans, the inverter, etc so you're using maybe 300+ watts just sitting there doing nothing.  So if you're using the 120V charger and putting 1400WH into the car then you're probably only putting like 1000WH or so towards the battery itself.

 

I was thinking in the past I could figure on putting in around 7KWH that I pay for and getting about 5KWH of use actually driving the car.  Though I haven't actually verified how many KWH my car does in probably a year.  And I just looked at my 240V EVSE and it's showing that it only used about 5.9KWH to charge the car last night including what it usually extra hours of the fan running in the car.

 

 

As for the state of your battery, I'd look at it in terms of them all being in varying states of decay.  But to get an idea I'd advise doing a full charge, reset a trip meter put it in EV mode and see if you've used around 5KWH or so at the time you enter hybrid mode.  That seems to be a decent battery.  I've heard of some clearing maybe 5.5KWH on a new battery and some closer to only 4KWH that are definitely degraded.










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