Acceleration tips? Battery care?

I've tried both for extended trials, and did not see enough of a difference to decide which is more efficient. So, if traffic permits, I try to stay in the eco range, but most times around here, even in the slow lane, you're risking life and limb if you aren't in a big rush to get to that next red light and stop again.

 

Yes you can switch modes in motion.

 

If one is going up a long hill, is it better to push into the power portion of the HSI to maintain speed, or keep it in the upper ECO mode (and lose speed)?

 

Pick your speed and push the pedal as much as needed. One thing that's been noted here in the past: it's more efficient to go up a long steep hill slower than faster. It is by far the biggest workout for the car.

 

If the hill is sufficiently long and steep, you'll have to go into the power portion. The HSI roughly corresponds to how much torque is being applied to the drive wheels, which directly correlates to how steep a hill you can climb. I discovered this when trying to keep it in the ECO range up a steep hill and was at about 15 mph and slowing down.

Also, going really slow up a hill can be less efficient than going faster. The Prius PSD acts like a torque converter in that a certain power level must be input in order to get torque out even at a dead stop. This "slip" is a significant source of loss at low speeds. Imagine taking your foot off the brake at a dead stop and applying the gas to just hold the car stationary or maybe creep forward a little. On a steep hill there will be a *lot* of power input just to move the car very slowly. Climing a hill at 2 mph only requires slightly more power than climbing at 1 mph, and you get to the top in half the time, so wasted energy will be cut in half.

Of course, at some point going faster and faster will begin to get less efficient as the power required to climb the hill becomes very large and that power is produced less and less efficiently by the ICE. My gut feeling is that on a 10% grade, maximum efficiency probably happens somewhere in the 30-40 mph range, just before the ICE starts revving over 3000 RPM.

 

Thanks, Mendel Leisk and tpenny67! I'm thinking of getting an OBD-2 device and Torque so that I can monitor the RPMs.

 

It's nice to have that data. What I seem to have discovered is that, in hybrid mode, if I keep the HSI power bar below the "Power" range and above the center line, that's pretty much the sweet spot for efficient rpm. If I've misinterpreted what I'm seeing, I hope someone will set me straight.

 

("Ahem!") uh, in Ireland, England, and Australia I have purchased the "Learner" signs and installed those in the rear window (a big "L" in Ireland, as I recall) so that the locals don't run me over whilst I am sitting on the wrong side of the car, shifting with the wrong hand, driving on the wrong side of the road , seeing oncoming traffic coming at me from the wrong quarter, and trying to figure out exactly where in the devil I want to go! It worked, however.

 

LOL! That brought back memories. When we were in England driving our cousin's car, he said he was wishing he'd gotten one of those for us. But people were MUCH nicer than here.

 

If you really want to get confused, try driving a right-hand drive vehicle on the right side of the road. At one of my jobs there was a small RHD truck that used to be a post office vehicle.
It is weird driving right next to the curb, especially with the sliding door open!

 

I didn't drive it, but our cousins in England had one right hand and one left hand drive vehicle. They said it never did get quite natural switching back & forth.

 

Close, the HSI is showing where the system is most efficient, not just the efficiency of the ICE. The engine RPM where you cross into the power range varies with speed. At highway speeds it does correspond to about 3000 RPM, but at lower speeds it's more like 2000 RPM. The ICE may still be operating efficiently in the power range, but efficiency is being lost because most of the power is going through the electrical path instead of directly to the wheels.

There's a really in-depth explanation of the HSI here: HSI. I recommend poking around on this site if you want to know how the Prius works in nauseating detail.
And here's a neat interactive animation of the power split device (based on the Gen1 Prius, so the RPM limits are off for other models, but the gear ratios are still accurate): Toyota Prius - Power Split Device

 

Thanks for the HSI link, @tpenny67. I'll mark it for later reading. Looks great. I knew that battery power entered into that power band equation, but I was trying to keep it simple and, to tell the truth, I'm still figuring it out. That link should help.

I've seen lots of neat videos on the power split device. An amazing invention.

 

Every time I watch one of those videos I fall asleep.