Energy recovery on over-run....

[lawnmowerman]

Hi all

 

Have covered about 1,000 miles on our Fabia 1.0 TSI DSG and am now aware that on the over-run the interior fan in the car speeds up. Is this an energy recovery system on the car to offset the loads on the system by the stop-start on the DSG cars?

 

Now that I am aware of it when the fan is full on it is quite irritating in traffic when the fan increases in speed (and noise).

 

Cheers, Bill 

[rum4mo]

Smart charging does mean not much in the way of battery charging unless it needs it and "lots" of charge, if needed, gets dumped into the battery during braking/over run situations on all modern cars.

 

I've connected a DVM to the 12V outlet once to see what is going on, I've never noticed the increase in fan speed/voltage on the over run, so something to check in the future, what  have noticed is the reduction in the fan speed when the car auto stops, most other voltage/power users don't seem to be effected, ie they seem to be supplied by a stabilised supply - things like lights for instance, I am talking here about how a 2015 Polo 1.2TSI 6MT behaves under these situations which should be the same as Ibiza or Fabia of the same age and fitted with "regenerative braking" .

[the_raz]

Using a OBDII-dongle and monitoring the voltage, I noticed that during engine brakeing, the voltage vent up to 14.7, when driving normally it hovers around 12.8-13.2, so clearly the charging increases when the engine is not producing forward motion.

 

This on a Fabia III 2018 1.0 TSI 

[lawnmowerman]

On 12/06/2018 at 10:23, the_raz said:

Using a OBDII-dongle and monitoring the voltage, I noticed that during engine brakeing, the voltage vent up to 14.7, when driving normally it hovers around 12.8-13.2, so clearly the charging increases when the engine is not producing forward motion.

 

This on a Fabia III 2018 1.0 TSI 

 

Thanks for checking that.

 

Have you noticed the interior fan increasing in speed? It is the only thing that alerted me to it. It is quite intrusive - especially in town driving on and off the throttle. But I am sure that in time I will block it out.

 

Bill 

[the_raz]

I have not noticed that. I usually have the fan on automatic any way, so I don't notice when the speed changes.

[lawnmowerman]

16 hours ago, the_raz said:

I have not noticed that. I usually have the fan on automatic any way, so I don't notice when the speed changes.

 

Cheers!

 

Bill 

[Shenanigans000]

I have plugged a voltage meter in to the cigarette lighter (accessory) socket and have noticed the same voltage increase that "the_raz" found too - rises to about 14.7 volts on the over run.

 

And yes indeed the ventilation fan speed fluctuates. Also the windscreen wiper speed too!

[rum4mo]

Yes, that voltage surprised me when I checked it, so as expected if at all possible, "large chunks" of charge get stuffed into the battery on the over run, ie regenerative braking - of sorts.

[lawnmowerman]

2 hours ago, rum4mo said:

Yes, that voltage surprised me when I checked it, so as expected if at all possible, "large chunks" of charge get stuffed into the battery on the over run, ie regenerative braking - of sorts.

 

*** Clever little Skoda ***

 

Bill 

Edited 17 June, 2018 by lawnmowerman
Punctuation

[AGFalco]

I think what happen is that the alternator is only working/kicks in when you are braking.

So during normal driving you are not wasting power driving the alternator.

Unless the car senses that the battery needs charging.

 

Thanks AG Falco

[ScottishMechanic]

14.7V is the standard an alternator kicks out as it is the perfect charge voltage anything more is overcharge.. it it drops below 14.2V you have in issue but not when you are driving a full hybrid as voltage will be drawn by the generator/electric motor to supplement power for the ICE.. it sounds to me like everything is good here

[rum4mo]

14 hours ago, ScottishMechanic said:

14.7V is the standard an alternator kicks out as it is the perfect charge voltage anything more is overcharge.. it it drops below 14.2V you have in issue but not when you are driving a full hybrid as voltage will be drawn by the generator/electric motor to supplement power for the ICE.. it sounds to me like everything is good here

 

The reality is that all Stop/Start cars have either EFB or AGM batteries and these batteries can tolerate being maintained in a less than fully charged state, and can also tolerate getting charged at higher than usual charging voltages for short periods. This ties in with "regenerative braking" being the main way of getting charge back into these batteries while using otherwise wasted energy  from the moving but slowing car.

[briscaF1]

How does the overrun charging work? Is the excitation coil of the alternator altered to obtain different output profiles?

[nicknorman]

1 hour ago, briscaF1 said:

How does the overrun charging work? Is the excitation coil of the alternator altered to obtain different output profiles?

 

The engine ECU communicates with the alternator regulator to set the target voltage. When the battery is adequately charged this voltage will be a “float” value that doesn’t put anything into the battery, but does power vehicle electrical loads. When the ECU senses throttle closed and braking, it commands the alternator to a higher voltage such that some of the vehicle’s forward motion is converted into battery charge. Helps slow the vehicle and recovers some energy into the battery.

 

As you suggest, the alternator regulator achieves the set regulated voltage by varying the current in the excitation coil (normally known as the field coil, or rotor).