Recharging FFE While Being Towed & Applying Brakes

[jmueller065]

It seems the issue with flat towing is with the automatic transmission. Since the engine isn't running, then the transmission fluid isn't circulating. I don't know if this would be an issue with the FFE since there would be no difference if the transmission were turning because of the motor or the tires; since they are all connected together and turning either way.

On the majority of ICE Focuses with an "automatic transmission" its actually a dual-clutch manual that is computer controlled (the "6-speed PowerShift SelectShift transmission"). No traditional torque converter at all.
Thus for these automatic Focuses putting it in neutral really is disengaging the gears and there isn't any transmission fluid (just some gear oil like in a manual trans).

 

[davideos]

Sounds reasonable; so now I'm left to wonder again why there is a limit to the speed at which they can be flat towed. Actually, I don't really care .

 

[GREG]

A lot of interesting speculations here by various forum members.

The question, however, remains, "If an FFE is towed with all four wheels on the ground while in drive and while regenerative braking is being applied - does this constitute Level 3 charging?"

Such a possibility could revolutionize "charging stations" for a FFE if you follow my drift. Instead of plugging it in just drag it to and fro while applying the brakes when the car is in drive.

I have seen reports that when descending Pikes Peak - a short 15 minute ride - a VOLT was able to recapture 80% of its previous battery charge. Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier (see http://en.wikipedia.org/wiki/Rectifier), which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Not sure what the FFE has in this regard but if regenerative braking has to go through an inverter and suffer that 25-33% loss then it is not a very efficient designed system.

This article seems to cast more light on just what the limitations of regenerative braking could be. Be sure to read the comments.

http://www.driveforinnovation.com/regenerative-braking/

 

[Astrand1]

My guess is that when in neutral, there is some sort of mechanical clutch (or mechanical relay) that disconnects the wheel or the motor

I don't think so looking at the pictures. (I'm hoping Ford shows that cutaway model at the Detroit auto show in January--most likely not but they may have a display showing all their power options and may throw that up. If they do I plan to take plenty of pictures and inspect it a bit more than the two articles did.)

In addition, the FFE's motor is synchronous meaning that the controller has to create a rotating magnetic field to keep the rotor moving (by energizing different windings in sequence). As such I think the back EMF will cancel itself out as the phase angle of the rotor changes with respect to the windings.

Well I went to the LA auto show yesterday and Ford had a nice layout and among all the cmax's and fusions there were 2 FFEs with many crowded around looking and asking questions with of course no Ford people there to answer. I wound up talking to quite a few people telling them about the car. Anyway there was no display showing the electric motor. hopefully in Detroit they might have something.

 

[paw160]

A lot of interesting speculations here by various forum members.

The question, however, remains, "If an FFE is towed with all four wheels on the ground while in drive and while regenerative braking is being applied - does this constitute Level 3 charging?"

Such a possibility could revolutionize "charging stations" for a FFE if you follow my drift. Instead of plugging it in just drag it to and fro while applying the brakes when the car is in drive.

I have seen reports that when descending Pikes Peak - a short 15 minute ride - a VOLT was able to recapture 80% of its previous battery charge. Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier (see http://en.wikipedia.org/wiki/Rectifier), which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Not sure what the FFE has in this regard but if regenerative braking has to go through an inverter and suffer that 25-33% loss then it is not a very efficient designed system.

This article seems to cast more light on just what the limitations of regenerative braking could be. Be sure to read the comments.

http://www.driveforinnovation.com/regenerative-braking/

We should never look at regen as a form of charging for any EV. If for no other reason than the law of conservation of energy.

If you drove a FFE up and down the same hill continuously you will eventually run the battery dead no matter how carefully you drive. This is because of all kinds of energy losses you will incur plus the fact that regen isn't 100% efficient.

So the only way that regen can really charge a vehicle is by applying external energy (towing with an ICE for example). But even then physics tells us that the amount of power applied by the towing ICE must be greater than the amount of power being put into the battery (due to losses). So you are really operating less effiently than an ICE on its own...

I might be wrong but I'm not sure that there is any more efficient form of regen than switching back through the motor drive inverter.

One last thing (no to be pedantic...) but Level 3 is a standards term and has specific meaning. Really all battery charging is DC (it is all the battery knows). The L1 L2 and L3 standards merely define how the EVSE delivers power to the on board charger.

 

[hcsharp]

A lot of interesting speculations here by various forum members.

The question, however, remains, "If an FFE is towed with all four wheels on the ground while in drive and while regenerative braking is being applied - does this constitute Level 3 charging?"

As paw160 said, Level3 is a standard describing the type of power supplied by the EVSE among other things. Technically it's not Level 3 because the EVSE is not supplying any electricity - either AC or DC. Regen is already implemented with a rectifier in combination with the inverter to help regulate how much power is actually pulled from the motor.

Such a possibility could revolutionize "charging stations" for a FFE if you follow my drift. Instead of plugging it in just drag it to and fro while applying the brakes when the car is in drive.

Instead of "dragging it to and fro" you could just put it on a machine like a dyno which would only turn the wheels forward. It's still a bad idea for a lot of reasons. @paw160: conservation of energy is not relevant because he said it would be dragged, not driven under the car's own power. It would still be much less efficient than a normal charging station, whether Level 2 or 3.

Regenerative braking is limited by a number of factors including SOC of the battery, speed of the car, traction, temps of the battery, electronics, and motor, and maximum safe charging rate of the cells.

 

[magudaman]

I posted an new thread about tow charging and was pointed here!

So I ran some testing today to try to figure out how much regen energy is being produced at around 50mph average in L mode.

I have a hill that drops about 400 vertical feet over .80 mile about a 9.5% average grade (http://www.csgnetwork.com/inclinedeclinegradecalc.html

During that hill I took video of the trip meter and ended up with this:

• 
  TIME KWH
  3:44 7.6
  3:53 7.5
  4:05 7.4
  4:17 7.3
  4:31 7.2

We end up with 400 watt hours of power over 47 seconds

Bring it to watt seconds:
400*60*60 = 1,440,000 watt seconds / 47 seconds =

30638.3 watts!

That is a lot of power! 0 - 100% in 39 minutes! ;

Another interesting note, in my test for every vertical foot of change I got back 1 watt hour!

 

[hcsharp]

You're hitting the wrong button on your keyboard (or calculator). To get watt-seconds you take the watt-hours and divide by 60 and then divide by 60 again.

I posted an new thread about tow charging and was pointed here!

So I ran some testing today to try to figure out how much regen energy is being produced at around 50mph average in L mode.

I have a hill that drops about 400 vertical feet over .80 mile about a 9.5% average grade (http://www.csgnetwork.com/inclinedeclinegradecalc.html

During that hill I took video of the trip meter and ended up with this:

• 
  TIME KWH
  3:44 7.6
  3:53 7.5
  4:05 7.4
  4:17 7.3
  4:31 7.2

We end up with 400 watt hours of power over 47 seconds

Bring it to watt seconds:
400*60*60 = 1,440,000 watt seconds / 47 seconds =

30638.3 watts!

That is a lot of power! 0 - 100% in 39 minutes! ;

Another interesting note, in my test for every vertical foot of change I got back 1 watt hour!

 

[WattsUp]

You're hitting the wrong button on your keyboard (or calculator). To get watt-seconds you take the watt-hours and divide by 60 and then divide by 60 again.

1 watt-hour = 60 watt-minutes = 3600 watt-seconds

Looks like multiplication to me.

In any case, I think magudaman's numbers are in the ballpark. That is, 30 kW produced during regeneration doesn't seem outside the realm of possibility for the FFE (or any decent-sized EV). As another example, the Volt actually displays the instantaneous wattage being generated (as has been observed/discussed by Volt owners) and apparently is known to generate as much as 50 kW when regen is engaged at freeway speeds.

 

[magudaman]

I would not be surprised if our car does upward of 50kw. This was only regen using the L shifter and no brake pedal application.

 

[Jelons]

More reliable education knowledge of rectifier diode (http://911electronic.com/rectifier-diode/) in application as rectifier bridge is need to used here. Single-wave rectifier or half wave rectifier is the simplest alternating current circuits. The system is built on the basis of the voltage reduction transformer, the rectifier diode acting as a current rectifier and the load voltage.