I've read a number of postings on charging the traction battery when plug-in is not available. I want to make sure I have the facts correct. When you switch from EV to HV the SOC (perhaps a low value) at that time is maintained by the ICE in the same manner as for a non-plug-in Prius. If the SOC is increased by regeneration and you remain in the HV mode the target for the system is the original SOC at the time of the switch so you will tend to lose that extra charge through normal HV operation. However, if you switch to EV when the SOC is the higher value, then back to HV, now the target SOC is that larger value. Using that "stacking" method you can recharge the battery for later EV use without plugging-in. Certainly "saving" regenerated kWh and then using EV when appropriate is great for mileage when you can't plug in. Can you also save some of the ICE generated kWh when the system is at the high end of the target SOC by switching to EV then back to HV to reset the target to that slightly higher SOC? Of course this isn't very efficient due to conversion losses but it could be convenient to have more EV miles available for later use on a long trip.
there's no such thing as a free lunch. if you let the EV battery deplete in HV mode because of the lower target SOC, that means that the engine won't be working as hard and you'll get better MPGs as it depletes the battery. if you "stack" and maintain the higher charge, that means you won't be able to take advantage of those electrons until later. now, whether this is worth it depends on how you'll drive. for example, if you're doing highway driving at 55 mph, and after ending this trip, will leave the car parked for a while and need to run some errands at city speeds, you'll probably want to save the charge like you described. however, if you're doing highway driving at 75 mph, or won't be doing any cold-start city driving later, then you're better off "depleting" the extra regen right away, because running at 75 mph requires high RPMs. depends on where you live my parents in LA live right next to a hump that basically guarantees getting 2-2.5 miles of EV regen when you drive over it. People coming back from the Sierras will obviously have something similar. Taking 101 from the Golden Gate Bridge to Marin will net 1-1.5 miles of EV. etc. not everyone lives in the flatlands of Boston
Sierra Nevada foothill and Coast Range north and south of the Bay Area. We get our best mileage in our present Prius Three on trips in those areas.
Go up hill for 10 miles at 30 mpg, go down hill for 10 miles for essentially no gas, average is 60 mpg. Average speed is 40 mph which is where pulse and glide gets even better mileage. This is not a measurement, just a possible example.
That is like my daily commute from Woodland to Auburn. Going up maxes at 56mpg and coming down maxes at 85mpg. This was on my Three in the summer. I am eager to find out what the PIP can do with similar conditions.
Your could even do this: go up a steep hill for 10 miles getting only 20 mpg, then go down a different less steep route that returns to the same starting point, going 30 miles with no gas, thus getting 80 mpg...or the longer 40 mile route getting 100 mpg! Mike
Yes! I5 over the Grapevine is a good example. Going south its a relatively short drive to the summit and then a long downhill into LA.
Here's an example of mountain driving. It starts at an elevation of 450 ft on the hills in Rocklin, CA, proceeds to South Lake Tahoe via US-50 and returns via I-80. For the long steep climbs mpg is 28 to 30 while for the downhills it ranges from 220 mpg for a short steep run to 130 for the long run from Donner Summit to the valley. Over all the 128 miles averaged 56.4 mpg. Of course that is the display value and we all know what that means
You haven't looked at the numbers. Up hill @30mpg, down hill virtually No Gas as in 100+ mpg. See my actual trip measurements posted above for a real example.
In my experience, the downhill going SOUTH is too shallow, at least at the speeds I'm going. Going north, because it's a steep enough slope, I can actually get something.
That's a long drive for me…400 miles. I'll take every extra mph I can get. I miss my parents living in Granada Hills. I could do that drive in 4h45m reliably.
Here's essentially the same trip in my new PIP. Not included is the approximately 1.7 kWh needed to charge the battery, equivalent to about 0.05 gallons of gas in cost. The numbers don't all make exact sense due to integer-only values for mpg available in the PIP display. In addition to starting off with very good mileage through the somewhat flat city, battery charging on significant downhill areas (eg Pollock Pines to River crossing) helped. Stacking on the long downhill and some short uphills from Donner Pass brought the battery up to almost full charge to use on the flat lands near home. I used HV for all uphill areas even when they were short sections that were otherwise good for EV.
