Divert excess regen power to bank of resistors to speed warmup

That would theoretically help sometimes, but I'm skeptical such a system would help sufficiently to justify the added overall cost, mass, and complication. The surplus energy available from that hard braking will be a lot less than the waste heat that has already gone into the heating the engine etc. in the process of building up the no-longer-wanted kinetic and potential energy you're trying to recover. (An exception would be a trip that starts with an immediate major descent while the engine is still cold.) You might achieve somewhat the same effect more simply by using "B" mode to decelerate, which transforms braking energy into frictional heat in the engine.

 

I can imagine a 10 kW resistor bank fitting more easily on a locomotive than on a Prius. I wonder if it would be less bulky to just loop some fat wire around the engine block some, and have the inverter feed it AC at such a frequency that it inductively heats the block, directly.

We'll figure out how to split your patent proceeds later.

-Chap

 

I vote for a huge array of red LEDs on the rear bumper,to,absorb that sudden pulse of electricity. If I am braking that hard , I really want the person directly behind me to know about it!

To me it sounded like the B mode engaged a version of engine-compression braking, which would be more transferring the energy to compressing and heating air, no? Still trying to understand this dang thing.
While we're at it, does anyone have a list of the rules that keep the ICE on?
So far I have:
1. Start ICE 6 seconds after "READY" light illuminates on a cold start.
2. Start ICE if battery level is below 2 bars.
3. Keep ICE running if coolant temp is below about 95 degrees F.
4. Start ICE if demanded acceleration exceeds the available motor-powered acceleration.
5. Start ICE when speed exceeds 42 mph (hatchback).
But there are times when none of those conditions are true and yet the ICE either kicks on or refuses to shut off, and I am tearing what little remaining hair I have out trying to figure out what mode its in and why it insists on having the ICE running.
A little help, please?

 

i'm in, let me know when you've got the kits ready for sale.

 

Yes, throwing away energy by mechanically forcing an engine to spin faster is commonly called "compression braking," but most of the energy the piston puts into compressing air in the up-stroke is returned, spring-like, by the air to the piston during the down-stroke. Some of it admittedly isn't, but friction (in bearings, cams, rings, oil pump, etc.) is predominant.

3b. Keep engine running if cabin heat is requested and coolant temperature is below about 150°F.

You might want to study the warm-up stages that are described in a sticky thread in this site.

 

I think that the proposal is a complete waste of energy.............
maybe in the case of the resistor bank, one can apply a toaster over for the radical grilled cheese hour's devre.

 

If the air entered and left the cylinder at the same pressure, this would be true.

However, during compression braking, air enters the cylinder under the strong vacuum of the intake manifold (throttle valve mostly closed), then exits at full atmospheric pressure. The result is a fairly substantial power put into 'pumping loss', quite separate from the mechanical friction processes.

For another view, ignore the compression and expansion strokes, as those balance out on a traditional Otto-cycle engine without variable valve timing. (The Prius Atkinson cycle is more complex, but the end result is similar). Instead, compare the intake stroke to the exhaust stroke, which display considerable pressure differences.

 

Yes, there are pumping losses, but the amount of air so processed per cycle is relatively small with the throttle closed, especially at increased engine speed.

 

It isn't the mass flow rate that matters. It is the volume flow rate (i.e. cylinder volume times number of cylinders pumped per second) times the pressure differential. This adds up to several kilowatts.

The closed throttle increases the pressure differential and strengthens the effect. An open throttle lets a lot more air through, but shrinks the pressure differential and total loss from this particular mechanism.

 

fuzzy1,

You are correct. My previous statement about the low mass flow rate was true in one limited sense, (loss due to throttling flow at the throttle valve itself), but I admit it was inaccurate in the bigger picture, mainly because it didn't consider what happens during the exhaust stroke, specifically the increase in cylinder pressure due to back-flow. That pumping loss would of course occur even if (hypothetically) the throttle were closed completely air-tight.

Nevertheless, I still maintain the common "compression braking" expression is inaccurate. Closer, although cumbersome, would be "suction (pumping)+friction+miscellaneous-losses braking." "Friction" can be further subdivided into several categories.

Thanks

 

I don't get this proposal. All the energy you generate by braking goes into the HV batterypack anyway. So why waste it in a resistor grid? If it is the limited amount of energy you can generate, that is due to the size of the electric motor. A Tesla can generate 60 kW of brakingpower since it has much more powerful electric motors. So instead of adding a (pretty much) useless resistor grid, just fit a bigger electric motor.

 

Get a toaster oven and rip of the benefits with the grill cheese!!!!

 

I had assumed Consumer Reports 32 MPG CITY rating was bogus as nobody sees that low. Do we know why CR gets 32 MPG? Cold engine I was thinking.

 

what do we care about normal people?

 

Ok, I what I mean is "as long as you keep your braking in the CHG region".
That's why I say it is a better option to fit a bigger electric motor so you can brake harder electrically. That way, all the regen braking can be used all the time (as long as the HV battery is not full, but you can use that, as you say, for electric heating).

My point is: better fit a bigger motor than a resistor grid.

 

A bigger motor will just make the car heavier.

The limiting factor for regen today is the limited charge rate of the battery, which cannot accept anything near the 60 kW capacity of MG2.