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Discussion Starter · #1 ·
I read one post on this topic, but did not see a complete answer. I'm considering buying a Prius. It will be great for my 80 mile round trip commute for work. But I also frequently drive from the Front Range of Colorado to the mountains for skiing. This involves a 50+ mile sustained climb in I-70 for over an hour. It ends with a very steep climb to a 12,000' pass.

I have heard some reports that this drive may be sufficient to drain the Prius batteries leaving me with only the gas engine for the last climb. Clearly 70 some odd horses will never get me up these hills very fast. I've heard reports of having to slow to 45mph (this is a 60-65 mph Interstate highway section.)

Does anyone have any first hand experience with extensive mountain driving in a Prius? Is what I have described likely to happen based on how the Prius operates?

Thanks for your help!
Rick
 

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didn't we just flog this topic to death recently? I recall discussions of Italy, Colorado, pink, green, blue bars, and the like. Or maybe it was a figment.
 

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Discussion Starter · #5 ·
I apologize if I didn't find the recent "flogging" of the topic. The Yahoo post above was exactly what I needed - thank you! There were even descriptions of the very route I intend to drive regularly. Summary: Looks like the Prius does great on sustained climbs - even though the batteries do get depleted.

Thanks for the help!
 

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S'ok. Sorry I sounded cranky. I guess my point was that you might be able to find an extended discussion (not necessarily under a topic heading that includes "hills" or "mountains," since this forum does wander off topic a bit :::snort:::) using the 'search' feature.

Happy Hilling! :) I live in the Land of Flat, so hills aren't an issue, really.
 

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hills...

I've done the I-70 corridor last sping/early summer. The Prius did great! Kept up with 65 MPH traffic, battery got down to 2 pink bars, but you keep getting it all back on the other sides of the passes. Amazingly smooth in holding speed. No issues at all, except for the slow SUVs and smoking diesels. Instant MPG readings were right around 14 on the upsides, and 99.9 on the downsides. Averaged 47 MPG for the trip from Denver to Telluride and back. Included a snow squall at Loveland pass/Eisenhower Tunnel. Temps were 60, then 28, then 40, then back to 60F. What a great car!
 

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No problem in the Rockies

Traveled from SLC, UT to Medford, OR today across northern Nevada and southern Oregon. I could tell when the battery was loas as the engine would rev much higher than "normal" but had no problem maintaining 70MPH + cruising speed.
BTW the tops speed limiter kicks in at 107MPH (confirmed on GPS)
DBird
 

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Re: No problem in the Rockies

dbird29 said:
Traveled from SLC, UT to Medford, OR today across northern Nevada and southern Oregon. I could tell when the battery was loas as the engine would rev much higher than "normal" but had no problem maintaining 70MPH + cruising speed.
BTW the tops speed limiter kicks in at 107MPH (confirmed on GPS)
DBird
Better be careful, the state police here in Oregon are throwing the book (the whole encyclopedia set, actually) at speeders they catch going over 90. (I just got an $861 ticket [yes, $861. I had to read it three times to make sure it wasn't $361, which I considered outrageous enough] for doing 82 on Portland's highway 26, where EVERYONE does 70, and it's not unusual to see 90. A Camaro was even going faster than me two lanes over, so I threw a fit when the officer didn't pull HIM over. That probably didn't help my cause. Needless to say, I'll be at minimum showing up and trying hard to get the fine reduced, largely because the ticket claims I was in a construction zone, and that highway has been 100% finished for over 2 years now.)
 

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Pulling hills is not an issue. I have done a few hill climbs, but nothing more than 10 miles long. I-90 at Vantage on the Columbia has a pretty steep climb on the eastbound side of the road, and had a longer more gentile climb on the wesbound side. The vehicle just doesn't bog down when you are pulling hills. The engine tachs up and you continue to pull the hill at whatever speed you have the car set at. Most of the time I pull a long hill in the passing lane because the car just keeps pulling the hill almost regardless of incline. I haven't ever driven a car that has this remarkable ability.

On the flip side of this issue is the annoyance of leapfrogging in hilly terain. When you are in the passing lane going up a hill at the speed limit, but are passed going down hill, at the speed limit, by everyone who was stressing going up the previous hill. I hate that because the folks you end up doing that with just seem out of it and like poor drivers.
 

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Top speed just 1 time

Only needed to see top speed 1 time as fuel economy at 100 MPH was only 25MPG.
Of course had to play on the way down, 90 MPH was 30 MPG, 80MPH was 35 MPG, 70MPH was 40 MPG and 60MPH was 48MPG.
Looks like the sweet spot would be 55 MPH but I can't stand to drive that slow.
 

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Losing power climbing the Rockies

I have experienced the a sudden loss of power at least three times while crossing the Rockies (or the continental divide, which I think is the same thing) with my 2001 Prius. After almost continuous climbing for an hour at highway speeds of 75-80 (I think the speed limit was 75), suddenly my cruise control (something I had added myself) let go and my speed dropped to about 55 with the gas peddle all the way down. Clearly, the battery pack was sufficiently deleted that the computer refused to use it any more to augment the gas engine. Perfectly understandable. But I'm glad I don't do that trip several times a week.
 

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I wonder how the 2004/5 would do on that climb, with the higher power and revs available. You might not find its limit.
 

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I can only add a testimony concerning the "classic" (2001) Prius here. Living near the Pyrenean Mountains in France, I have absolutely no problem climbing long and steep mountain passes. In almost five years I did encounter the "no more assist" situation but it was in very special cases (for instance Mont Ventoux, 1600 m up in 23 km long) and because of rather aggressive driving.

I gave recently some talks about hybrid cars and for that purpose I made some measurements thanks to the invaluable MiniScanner made by Graham Davies. I decided to look for a long enough, steep enough road in my neighbourhood and found a 12 km long, 8% steep road to a ski resort. I started driving aggressively from the bottom, even though the battery was rather low because I just had been driving on electricity through the small city in the valley. I did get at the top without loosing battery assist, although I was not far from it : the battery works in the 40%-80% SoC range and I went down to 44%.

What surprised me was that I was charging the battery at the beginning, not discharging it ! :shock: Of course I dit not push the pedal to the floor but simply because I would have been driving too fast at that time... :) Actually the battery was discharged when I was re-accelerating after tight turns, but was also often charged as soon as I was obliged not to use the max power because of the road. You can see below (apparently you need to log in to see it) the time evolution of battery state of charge (in pink) and current (in blue, positive means charging, negative means discharging the battery). There is a void in the curves because I had to stop a few minutes for changing recording parameters. Note that the vertical scale corresponds to the whole usable range of battery state of charge.

The whole talk has been turned into an HTML version here. Unfortunately for most people reading this post, it's in French. I'd like to make an English version later, but it takes time and effort... :wink:

Now, don't forget this was a 2001 Prius, and the present version is supposed to perform better. 8)
 

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Sustained hill climbing

Thanks for the link and the work, Frenchie. Also to mention another of Graham Davies' gifts, a spreadsheet model of the NHW11 (2001-2003 model year) Prius. This is in the files section of the yahoo group "Prius_Technical_Stuff".

I put 8% upslope into the model and looked at the total KW required to maintain different speeds, along with the estimated total energy losses on board. Whenever this total is less than the KW obtainable from gasoline combustion, that speed can be maintained without battery depletion. At least, this is what I am assuming here.

If the NHW11 provides 52 KW maximum, it should climb 8% at about 72 mph. In the US at least, highways of greater than 6% slope are rare.

If I dare extend this to the NHW20 (2004 onward model) with its 57 KW, it should climb at about 77 mph.

DAS
 

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You're perfectly right. Actually, in my case (and in most common ones) I was draining the battery when accelerating hard after sharp turns (which are frequent on such roads). Every negative peak in the chart corresponds to such a situation. You can count how many turns had this road ;).

Otherwise, unless you want to drive at unreasonable speed the thermal engine power is enough, although it's a bit noisy.

Not only the NHW20 engine is more powerful, but its maximum power is available at lower car speeds than in NHW11 because of the increase in MG1 max rpm. I think this feature is even more important in such situations.
 
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