Why Can't Plug-In Prius Recharge Its Larger Battery?

Feasibility, I should think. How could the car know when it was about to be parked near a recharge point, and thus that it should allow the plug-in batteries to drain so that they can accept a nice non-fossil-carbon charge? (Of course without a non-fossil source of electricity with which to recharge them, the whole exercise would be pointless from a global warming perspective.) Simpler to just use 'em up immediately and then drag them around.

Speculating further: the usual non-plugin battery is already about as large as it needs to be, enough to hold the energy of one launch to about 60 MPH. Making it bigger might improve fuel economy fractionally or increase battery life, but all of that energy would ultimately still come from the fuel. In contrast a plugin-only battery guarantees a more significant reduction in gasoline consumption and therefore a greater increase in MPGs. Whether that also results in a net reduction of fossil-derived CO2 depends on what the user plugs it into.

 

I posted a question and article about this yesterday on another thread, but I'm wondering if it has to do with the battery type. Is the "hybrid battery" a regular Prius NiMH and the EV packs are Li-Ion? I was thinking perhaps there is a reason there. However, the article suggested that it had to do with circuit switching between the battery packs. I'm not sure if they meant that it wouldn't be efficient to regen into all 3 packs at the same time, or if opening and closing the circuits on the fly is not easily feasible.

 

I don't understand the confusion. It all makes perfect sense to me. First of all, I have a plug-in kit in my prius and it is really no different in this regard.

If I hit the brakes down a long hill, the prius regenerates into the regular hybrid battery that it has. When I take off again, the power is used from that battery.

Why would i need to recharge the additional (plug-in) packs using regenerative breaking? It would be nearly impossible to generate enough power to use such a feature unless I was driving down a mountain or something.

There would be additional cost in adding that feature, and I doubt it would get used much.

 

Perhaps the regen wattage can now be increased; so you can generate more and friction brake less. This would mean that you can capture more watt-hours per trip than you can with the current Prius.

The more watt-hours you can regen, the more watt-hours that can be applied to accelerating, and the less the gasoline that you will need.

 

the relays have to race to open and close as energy is being stored or depleted. this is a very expensive and unnecessary addition, especially given as others have stated that regen does not create enouugh electricity to use those batteries efficiently.

 

Assumption...OR:

The way I would do it....

If the standard hybrid rechargeable battery happens to have sufficient charge I would use that up FIRST and then only switch to the use of the Grid chargeable batteries if no regen were immediately available for the hybrid batteries.

As long as the "standard" hybrid battery could be sustained at a reasonable charge level, using regen, NOT the ICE, that's where the drive energy should come from.

Any regen opportunities that might "happen by" I would direct to the standard hybrid battery.

Make PERFECT sense to me.

Basically I see no reason to provide the additional electronic switchgear to use regen, or even the ICE, for charging anything other than the standard hybrid battery.

Sort of an additional aside....You would only have need to use regen for charging the Grid batteries if there was so much regen available as to "overflow" the standard hybrid battery. And if you given priority to the use of the standard hybrid battery there would be little occassion for a regen surplus.

Okay..?

 

That's why Porsche chose to use a "flywheel" for short term energy storage in the new GT3 hydrid. Batteries cannot absord the extremely high surge currents fast enough to take full advantage of hard to severe braking effort.

 

This sounds like a parallel battery arrangement, where regen flows passively to the lowest voltage sink.

Guessing here -- may be *way* off

 

Well, perhaps you should visit Portugal
Northern Portugal is hilly, and many times B mode does mean ICE revving hard, due to overfilled battery...If a long descent energy, like from Vila Real to Amarante, could be stored, at least further 20km would be driven EV only...

 

Actually, Pack 1 and Pack 2 are recharged by regen, at least until depleted and pulled out of the circuit. For these vehicles in the test fleet, they didn't want to stress the SMRs used to put the packs into use by constantly flipping them on/off for regen once in depleted mode. The SMRs are simply used to get one of the packs into use until depleted, then used to flip it out of the circuit.

Remember, this is a test fleet - there is no guarantee that the PHV that finally goes on sale will use this same system or not.

 

Sounds like they just put an Enginer pack in there!

 

The factory pack runs at 345V - the Enginer isn't anything close to that, now, is it?

 

This is precisely why any contactor-based third-party PHEV kit that
doesn't control cross-currents, a la calcars, is doomed to fail.
.
_H*

 

the GT3 is turning out to be amazing new technology. toyota could take a lesson from them.

 

I would not make it so simple.
GT3 is a sports car. The way it brakes it so different...and the time of re-using energy is very brief.
Everyday use of a car has long and light braking, and resuming throttle much later.
IMO, any aditional rotating part is more of a trouble, considering actual layout which is proven and capable of absorving a good part of the energy.

 

Tell me if I'm wrong about this:
When you brake and the Prius goes into Regen and the bar on the HSI goes all the way to the left in its box, it means that regen braking is producing energy faster than the traction battery can safely sop it up. So some of it gets lost.

It seems to me this happens enough (in my driving at least) that being able to use that excess regen to recharge the plug in battery. The reason that regen works at all (for fuel savings) is basically that it recaptures the kinetic energy of motion as potential energy for the battery, rather than wasting it as heat. If you regularly had to use fuel to generate the electricity, you would be saving nothing. Am I nuts?

As a non-engineer, I also don't understand why there are separate batteries for plug in and regen charging. It would seem to me that electricity is fungible, and it would be cheapest to have a single large battery that gets charged--by the plug or by regen braking--whichever is working at a given moment.
Is there a reason this can't be done, or can't be done economically?

 

Hi Kgall,
No, you are incorrect. All of this engergy does go back into the Prius HV battery. The Pruis is very good in recapturing this.

Yes, The regen feature can recapture about pecentage of the energy. You lose about some everytime you convert from electrons to motion and again when you convert from motion back to electrons. So you are better to not accellerate so much that you need to later use the brakes, even with regen.

No, The Prius also saves fuel by running the ICE in its most effeicent mode. This includes things like sometimes running more power during lite usage times and storing that extra energy to use later.

Thanks,
Dan

 

And ideal hybrid would NEVER make use of the frictional brakes as long as the hybrid battery could take some charging. But the fact of the matter is that current battery technology does not allow for the type of high surge current charging that everyday braking, regen braking, would require.

So an intermediate storage method, flywheel, compressed air, seems to be the answer at the present time.

"Pour" more, ALL(?), of the braking energy, using regen braking, into compressing air or spinning a flywheel, and then "meter" it slowly into the hybrid battery.