MPG "The Perfect Method"

From Sac to Reno then through Tahoe and back home is a heck of a lot more miles. You listed a one way downhill trip. You should include total mileage and FE from the trip up the hill as well. Otherwise it looks a bit disingenuous.

 

Unless you are paying more for electricity than gas per mile (in which case why get a plug-in?), this sounds like an unsound financial decision. Not 'perfect'.

 

What is the point of having energy stored in the battery if you don't use it? If you are just using techniques to have the gasoline engine charge the battery (through regeneration), why not just get the straight hybrid? The only rationale I can think of is to take advantage of the larger regenerative capacity if there are long up/downhills, but in that case one would never bother to actually charge the car.

 

I guess I indeed am still missing the point Using HV to go up hills and EV going down is just using the ICE to charge the batteries, via the indirect way of using the ICE to gain potential energy climbing the hill, and recovering the potential energy on the way down the hill via regeneration into the battery. If I am missing some fundamental point, I apologize. I really am not trying to be obtuse.

 

If you used HV at any time when you could have used EV, you are wasting gas. If you have so few opportunities to use EV that you end up with the same as you started with, you are probably wasting a Pip, and could have done it all with a regular Prius. There is no way to save both gas and electricity by switching between them (hypermiling will, of course, save on all energy). If gas is more expensive per mile, you want to arrive home with the last of your battery energy.

 

Your goal is good, your logic is flawed. Given you live in Sacramento where electricity is cleaner than gas, to burn less gas and produce cleaner air, you should alway arrive home with the battery at minimal SOC, i.e. in HV mode with 0 EV miles remaining.

Your technique may improve your overall MPG on the middle section of the trip, but the last 12-15 miles you should switch to EV mode, and use zero gas and hence the overall MPG would be higher.

But the reported data is insufficient to support any conclusion. Without knowledge of the gain from elevation, the energy reported via MPG is out of balance.

This is actually not quite true. The describe technique could be beneficial in reducing gas and still allowing more efficient use of the electricity. If one must use gas, you can save on both gas an electricity by switching/blending, if it helps keep the gas engine in its ideal BSFC points and keeps the current demand in the EV motors lower. Both the ICE and the EV have non-linear losses so more power demanded by either one alone reduces their efficiency. Its also a function of road-load not just speed so its hard to know where the optimal trade would be in a PiP. But if one must use gas on the trip, then the technique may have validity.

But it will never be more efficient to return home with EV miles. The EV mode is more efficient and so the goal should always be maximize the use of that fuel.

 

Right, but I am presuming that Toyota knows. So HV mode should balance gas and electricity energy in those situations when some gas is needed. A driver should thus be selecting HV or EV modes depending on the one thing they know, that Toyota doesn't, namely the character of this particular trip.

 

Agreed that Toyota knows a lot more than all of us combined. Not clear what you mean by the driver selecting the mode for the trip, but the operator can still do more than just selecting one mode for the whole trip .

The car cannot predict the future,and the driver can. The driver switching to EV as they go down a hill or head to a stop can get the car to shut down the ICE before the reactionary control systems can do it. The driver can anticipate where they will be better able to use EV (e.g. sections with lots of stop/starts), and where there will be larger hills (and save some added EV buffer for those).

 

oh well - so much, for the 'perfect method'

In reality, you need to count every day, month after month, year after year . . . . hills . . . . . cold . . . hot . . . etc to get 'the perfect method'. That way, results count for everything, every condition, based on season after season of variability. There are folks on the boards who've accurately logged their process for years and years of driving ... 100's of thousand of miles. Now THAT's accuracy. I've been keeping a log of our EV range now for over 16,000 miles, so I can safely say what my real world results are. The next variable I'll starte to notice - i suppose - will be traction pack degradation. It's just a matter of time.

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Because I didn't say the driver should be selecting a single mode for the whole trip. I said they should select which mode to be in (at the moment), based on their knowledge of the character of the trip.

It possible in the near future that Toyota will create a car which takes advantage of all information sources, and require (or severely recommend) that the driver input the destinations (until next charge). The car can then know routes, elevation changes, up-to-the-minute traffic, all to a higher accuracy than the driver knows. The car would thus be able to make most efficiency decisions better than the driver. This, to me, is the only reasonable reason to have an integrated navigation system, and it currently isn't done to any extent.

 

I'm currently doing research in this area. I'm aware of some patents in this space from

• Patent US20020188387 - STRATEGY TO USE AN ON-BOARD NAVIGATION SYSTEM FOR ELECTRIC AND HYBRID ... - Google Patents
• Patent US20050228553 - Hybrid Electric Vehicle Energy Management System - Google Patents
• Patent US7958958 - Inputs for optimizing performance in hybrid vehicles - Google Patents

and GM has a number of patents in the space, e.g.

• Patent US7539562 - Hybrid vehicle powertrain control method and apparatus - Google Patents

And some EU patens from MB (for trucks if I recall) and VW/Porche but I don't think I've seen any from Toyota. Do you have any references to some?

The closest to this being in use is for fleet trucks.. and its more route planning/optmization than load-following or hybrid control work.

 

No, it just seems the obvious next step.

 

I find that if I get on the freeway and switch to HV mode, it will still use my EV charge until depleted. I cannot find any way to "save" the EV range.

 

not quite sure what that means - are you trying to say that the lowest elevation is different on 1 side then it is on the other? Because ultimately - after you make a round trip, from 1 side to the other and back - you have necessarily covered all of the variables, regarding altitude changes.

... There you go - give that man a cigar.
;-)


SGH-I717R ? 2