Suprising Energy Screen Display

[curtissac]

This weekend I finally took the opportunity to run my Prius up in the mountains. Sac to Reno, and back for a family get-togther.

I noticed an unexpected display on the energy screen of the MFD. I know that the MFD is referred to as eye candy and doesn't necessarily give and accurate depiction of what is happening, but like I said, this is not something I would expect to see...

On eastbound I-80 coming down the hill from Donner to Truckee, it's probably 3 miles at 5-6%. The CC was set at 70 for the entire ride, but of course the speed ran up on this downgrade. But while the speed was running up, the energy display showed the ICE sending power to the wheels. I was expecting to see blue regen arrows from the wheels, but instead I saw orange arrows going from the ICE to the wheels and the elec. motor, and yellow arrows charging the batteries. Cruise control off, foot off the pedal - still looked the ICE was pulling the car down the hill.

If I stepped on the brake I got blue regen arrows as expected. Took my foot off the brake and orange arrows came back.

Going from D to B gave regen arrows. Back to D and the orange arrows came back.

This was happening between about 68 and 78 mph over the course of a couple of minutes. I normally would keep the speed under 70 in this area, but I rode it out to see all this stuff happening.

Any ideas what the MFD was trying to tell me?

Notwithstanding this brief, wierd energy display, the car ran the Sacramento-Reno trip just fine. I don't normally go all the way to Reno, but I do a few trips up to Truckee and Tahoe each year. This was the first time the Prius had been east of Auburn. I normally run the climb to Donner at 65 or less in my other cars, but I decided to prove that the Prius could keep up with the big dogs on this trip. Not disappointed.

The engine was really wound up on the steeper climbs to Blue Canyon and then up to Donner, and the batteries got down to one purple bar at the tops of those, but it kept the speed steady. Got just over 30 mpg up to the summit. Coming down east side through Truckee and into Reno, the numbers went up and the one way trip averaged out to 44.3 mpg.

The trip home today was in heavier traffic and cruise control wasn't practical as all the cars were changing speeds on climbs and decents. The one way mileage back to Sacramento was 59.6 mpg. Note that I never saw the wierd energy display on the way home, and there were several places where I would say the conditions were the same (5%-6% downgrade at 75 mph).

[dreichla]

Although I don't use the CC, that happens to me all the time on a steep grade I take home from work every day.

The bars are full green by the time I get to the bottom of the hill and the engine is racing wildly. I usually pop it into B to keep from having to use the brakes as much. The wild racing bugs me toward the bottom, so I switch to D and the racing stops.

From what I gather, this perfectly normal occurrence is the car's method of protecting the batteries from overcharge by running the ICE.

Someone here will give a more technical answer.

[curtissac]

Thanks. Only difference is that the batteries were not fully charged when this happened to me. They were about half charged according to the display.

I was guessing that it was the ICE running to keep the MG1 speed in check, but I was going less than 80 mph and in other similar situations I would get blue regen arrows. Still just seemed wierd.

[eagle33199]

Is it possible that, going into the downgrade, your batteries were low? the car could have simply been running the ICE to try to get some more charge into the batteries (of course, overcompensating since you were on a downgrade). With no real hills around here, i can't say for sure how it would work, but it seems to me that going up you'd use much of the batteries, then coming back down would recharge them, however it's possible the car is thinking it needs to run the ICE to recharge them since they got "so low".