Hybrid cruising speed

Many times there is NOT a one size fits all Primes explanation of how the car behaves.
The car, most of the time, behaves differently when being driven at different speeds, 110 km/h / 68 mph, 80 km/h / 50 mph and 60 km/h / 35 mph.
Which mode you are driving in and how much EV range is showing can change the behavior too.
Many other variables also effect the threshold of Engine to Motor.
From what you've posted above, without including at least a few more details, it sounds like the car is behaving normal enough. Although the thresholds of ICE to EV and Charge to Discharge can and do vary widely at different speeds and in different driving modes, etc..

 

I've found that if the battery temperature is below freezing, the car will sharply limit the amount of battery power that you can draw. You might be able to cruise at highway speed on battery, but one stomp on the accelerator and the engine will start. The same would apply if you started up a hill or hit a headwind. I don't know if this behaviour would get worse as the temperature fell.

 

Those are essentially one in the same.

 

I know you posted "Hybrid Cruising Speed" but it sounds like you are in EV Auto mode. If so, then the engine kicks on above a certain speed and also when you accelerate briskly.

I read power demand as torque vs. the speed maintained.

 

You're geting really close there, @Henrik Helmers.

It's related to how much power is required to maintain your speed. The car is programmed to try to run at the most efficient throttle setting and RPM. So, if that setting is less than what your speed requires, it puts the extra energy into the traction battery. At some point, it decides that it's done that long enough and shuts off the ICE and uses what it's been stashing in the battery. Eventually, it uses that up and restarts the ICE. Rinse and repeat. That's way more fuel efficient than running the ICE at a low throttle setting and rpm wile driving at a low speed. On flat ground, the limit seems to be about 60 mph. Above that and it won't switch back & forth. Or if you're going uphill or into the wind. The lower the speed, the less power is needed so the more it will put into the battery so that it's running at its most efficient throttle setting.

 

That's why pulse and glide is so good at achieving high MPG. Using gas to get up to speed and then releasing the throttle enough to shut down the ICE and then keeping it in "golf cart mode" until another speed boost is needed can dramatically improve mileage in HV mode.

 

The best results I've achieved in terms of overall energy efficiency is to use EV for flat or downhill segments of a trip (in the bottom half of the HV display) and HV for acceleration or uphill (the upper half of the HV display). Of course, if you can make the whole distance between charges on EV, that's the best.

 

That's exactly what it's doing at speeds under about 100km/hr. On long runs at about 80 kph, it's just keep going back & forth between using EV and using ICE. It get amazing fuel efficiency that way.

That depends on the highway speeds. If I''m going much farther than my battery range I'll use the EV at lower speeds and HV at expressway speeds. I experimented with CHG mode and, at best, it broke even. At expressway speeds, CHG mode loses. A lot of people like to use CHR mode if they don't have any EV range left and want to make some before they get into the city driving. I find that the Prime in city driving spends so much time with the ICE off that it probably burns less fuel in HV modes on city streets than what it takes to produce EV range on the expressway at high speeds.

If I''m going maybe 40-50 miles, I just drive it and let it do its thing.

 

Yup! It sure is. That's why I don't fuss about having EV range. It's nice to have, but If I run out, I run out.

 

Assuming I know upfront what my trip entails, I'll generally use EV (fully charged or mostly) to get to the highway, then switch to HV. Then switch back to EV when I'm off the highway (or going under highway speeds).

I like to keep the traction battery not fully charged when driving, as, from my understanding (which could be wrong), if it's doing the charge/discharge in HV mode at < 60mpg, it would be slightly more stress on the battery. Granted, fully charged is really ~84% or so, which is about where the stress level starts to increase a lot, so by the time EV mode gets me to the highway, it's down a bit, so it probably doesn't matter too much.
(same at the bottom end with the discharging, but the bottom end is still pretty high so it isn't as big of a deal).
Ideally, I like to cruise in HV mode around the 50% mark, but plenty of room for error there.

Yes, I micromanage it a little too much! Gives me something to occupy my mind with.

But CHG mode really is of very little use, unless you really want a full EV mode at the end of the trip, and that's probably a niche use (campground in the middle of the night, perhaps, or sneaking into your house is all I can think of).

HV mode is very efficient! Best to keep EV mode for non-highway use.

 

EV mode on the highway is more efficient than HV as long as your path is close to level or downhill.

 

True as far as it goes, but EV mode on the highway is the least efficient way to use the battery power. You'll get more miles per KWH at lower speeds.

 

Miles per kWh is dependent on power required to propel the vehicle. It's not true that it always requires more power to maintain highway speed than to drive on surface streets. In fact, my driving experience is the opposite. I average about 6 miles/kWh on the highway and closer to 4.5 on streets. Constant traffic lights and stop signs take a toll over highway driving.

 

Some history:

There is a rev limit to M/G 1, M/G 2, and the engine, your car will not let you exceed these.

In the Gen 1 and Gen 2 Prius above 38 MPH the engine had to run to keep M/G 1 from over revving.
112 MPH was the rev limit of M/G 2

In Gen 3 the limit for M/G 1 was raised to 62 MPH. 115 MPH was an artificial top speed, perhaps limited due to tire loading. (The v had different gearing and 43 MPH was the limit for M/G 1 without the engine, and 103 MPH was the limit for M/G 2)

In Gen 4 and the Prime, M/G 1 has an even higher limit. (82 MPH?)

Professor John Kelly goes over each generation

 

As mentioned several times elsewhere on PriusChat, CHG mode was designed for drivers who need to commute into cities in Europe and elsewhere which limit access to zero-emission vehicles during certain times of day. One can drive on the motorway using the ICE and then switch to EV in the city center.



Although sneaking into your house late at night might have been an undocumented Toyota design consideration, too.

 

The alien spaceship noise from the AVAS wakes my daughter up every time I pull into the driveway. Her bedroom window is right above the garage. There's also no quick way to kill the lights at night without being blinded by the dash display since for some inexplicable reason the brightness adjustment doesn't affect the brightness of the display when the headlights are off.