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Opposite direction here refers to flow of electricity and not physical rotation of the motor (Sorry, I corrected my sentence).

When the vehicle is accelerating it draws current from batteries and from this magnetic field is created and hence motor rotates, when decelerating the rotor is rotated by an external force (Wheels in this case) hence it acts as a generator and hence it generates electricity, which is fed back to the batteries.

Hi,

i do not understand why is it so, what happens if this is done, could you explain?

Spike

You do get back-EMF current if its a permanent magnet type of motor.

Hi Spike,

When you are driving it is a mix of both accelerating/decelerating, and hence its safe regenerating the power, because this regenerated power will further be used when you again drive.

But when you continuously tow the vehicle, regeneration happens cumulatively and will lead to thermal runaway which might affect the batteries.

Thermal runaway explained:
http://en.wikipedia.org/wiki/Thermal_runaway.

Hope your doubt is clarified?

Hi,

thanks for the explanation, no, I am still not clear:). As per my understanding goes, the charging and discharging happens only till a specified SOC, it is not allowed to exceed the limit through closed loop control.

Does this solely work on charge depletion mode? What level of SOC is allowed for charging and discharging?

Thermal runaway is not the reason , me thinks, more so IF it has a battery monitoring system !

Spike

EDIT- I think we are hijacking an ownership thread, if you don't mind, could you start a new thread on electrics and hybrids, would be interesting to learn a few things.

The charger has the ability to cut off power (after 100% SOC) if it is coming from an electric source, but since regeneration is happening from an external source(through kinetic energy of wheels), the charger has no role to play in cutting off this energy.

Hence regeneration happens continuously leading to thermal runaway.

Pardon my ignorance - the charger as I understand, is an electronic circuit board that conditions and monitors the charging current & voltage that is to be fed to a battery pack - and the regenerative braking system simply generates an input voltage to this charging circuit. Now, where does thermal runaway come into the picture?

Think of it this way - you are trying to fill a bucket with water from two pipes, one is the usual municipality water supply and the other is from rainwater harvesting. The first one is turned on and off knowing fully well that it'll be there all the time. The second one supplies water only when it rains. But that doesn't mean that you should leave it open even when the bucket is full.

Thermal runaway of the battery pack happens if the charging and protection circuit fails and results in a drastic increase in temperature of the battery pack.

But then how does turning OFF the car help / prevent thermal runaway? (during towing)

Where does the generated electricity go? Or is the motor decoupled in some way?

cya
R

How is the power flow for this vehicle?

Battery>>DC/AC Converter>>Motor>>Axle (Positive drive)
Battery<<DC/AC Converter<<Motor<<Axle (Regeneration)

Is it different from regular electrics, am I missing something here? :confused:

Spike

Hi silversteed,

Charger can monitor the current & voltage fed by an electric energy source, but regeneration in an electric car happens when kinetic energy in the wheels are converted to electric energy and is then fed to the batteries.

And the charging unit in the e2o is designed to to restrict only electric current from a power source and not designed to limit the regenerated power (it may be restricted in other similar units as per requirement but not in this car).

Hence this excessive regeneration will lead to thermal runaway. Hope I answered your question.

During towing (when the vehicle is switched OFF), even though motor keeps rotating it cannot generate electricity because there is no magnetic flux inside the motor as the batteries are virtually disconnected.

Because of this thermal runaway can be prevented by keeping the vehicle OFF.

Agreed
Agreed

To me, apologies if it's offending, this is absurd!!! If I were to design such a system for my employer (who is an OEM for some of the biggies in both the dirty and clean automobile markets, btw), I'll be kicked out in no time.

You sure did, but would you mind sharing the source of this piece of info?

EDIT:
I checked your profile, now I know the source of info :)

EDIT 2:
Spike, you're right.

The powerflow of the vehicle is:

Battery>> DC Current >> Motor Controller >> 3 Phase AC >> Motor (Drive)
Motor >> AC >> Motor Controller >> DC Current >> Battery (Regeneration).

^^ Thanks, not much difference there with power flow.

Thermal runaway is an aftermath I feel and not the cause, may be experts here (with exposure to hybrids / electrics) can comment better.

Spike

No its not the question of the designer/design, but to my understanding there is a limitation to restrict the regenerated power (Regenerated power ~ 80-100 Amps as compared to regular power source ~ 40 Amps) hence during regeneration it can actually charge the batteries within 2-2.5 hours as compared to 5 hours during regular charging.

Hence this higher current developed during regeneration can have adverse effect on batteries.

Totally agree with you Spike, its an aftermath not cause

If that's the way you look at it, yes, you have a point. Probably I need to do some homework to think on the same lines and be convinced :) Different ways to solve the same problem...