By on May 7, 2009

TTAC’s very own David Holzman writes:

How high could a Prius or Insight climb before the battery would run so low as to cease contributing to horsepower? In other words, If I lived at the top of Skyline Drive and worked in Palo Alto (or had a similar commute somewhere else), would the electric boost cut out on the way home? How much elevation could either car cope with? And once the battery has bottomed out, how weak is the car going to feel? I’m guessing not nearly as bad as my then-8-year-old ’62 Falcon, which I could barely push over 30 in second, climbing the mountains in Wyoming, Utah, Nevada, and California. Still, would someone with this sort of commute want to avoid a hybrid?

Sajeev answers:

The short answer is you must always test a vehicle in your daily commute before you buy.

Here’s the long answer: hybrids with a small displacement IC engine don’t much care for hills. Or extreme temperatures: even my Lexus GS450h tester never went north of 25mpg, after denying myself the luxury of air conditioning in the heat and humidity of a Houston summer. Which is somewhat beside the point. But hybrids do hate less-than-ideal driving conditions far more than any other vehicle. Except your ’62 Falcon.

Right. So back to your commute: I can’t find any concrete info on battery life in relation to elevation and climate. I’m no Michael Karesh, but hybrids haven’t been around long enough to get a fair cost-benefit analysis in America’s diverse geographies.

Driving a hybrid in your conditions (using accessories like A/C and the stereo) is not unlike Captain Mike’s less than flattering test of the Prius. While you may not bottom out at Mike’s 17.5 mpg, odds are you will drain the battery on the way home, retiring the battery pack faster because of the daily cycling.  And rest assured, you’ll pay through the nose for that privilege.

A “clean” diesel might work better for this terrain. Whether or not it’s cleaner and more cost effective than a hybrid (or a gasoline vehicle at fire sale pricing) is up for debate. So, Best and Brightest, let’s have at it.

[send your technical questions to [email protected]]

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20 Comments on “Piston Slap: Holzman and the Hybrid Hill Climber...”


  • avatar
    djoelt1

    Datapoint: Trip to Sierras from SF in summer with two adults and bikes and luggage for a 3 day trip. Achieved 48 mpg average from SF to Kirkwood (a ski resort in the Sierra Nevada); although I track my M3, my buddy drove the Prius along the twisting two lane mountain road so fast it scared me and we still got 48 mpg. I think the limiting factor in your ascent to Skyline will be your skill in navigating the curves, not the power of the engine. Learn to drive the Prius and you will beat a Ferrari driven by a rookie. The new Prius I believe has a sport package for improved handling, no less!

    Overall for the trip, which included speeds far in excess of the speed limit, was almost 50 mpg by the time we returned to sea level.

  • avatar
    Redbarchetta

    I can’t speak for the Prius but this might give a clue about the Insight. When on our way to a ski trip driving from Denver to Vail up the mountains in our friends Civic Hybrid it was dog slow once the Battery was drained. My brother was driving and would gain as much speed while charging the battery on the short downhills just so we wouldn’t drop below 45 on the inclines. It was really pretty annoying and probably not idea for his battery pack in the long term. All i know is I couldn’t sleep in the back because the engine noise was too much. My brothers 300D would have been ideal for the trip and gotten us there faster if not for the snow everywhere.

    We were getting passed by semi’s on the inclines.

  • avatar
    buzzliteyear

    Point of order:

    The battery control electronics on hybrids keep the battery charged between about 15% and 85% of full charge no matter what.

    That’s what enables the battery packs to last 10 years/150k+ miles.

    There are ways to trick the electronics into running the batteries down further, but that involves multiple turn on/shutdown cycles in rapid succession.

    Excessive battery pack wear is probably a non-issue in this situation.

  • avatar
    tedward

    Without wanting to engage really in another argument about the Prius I’ll say that my experience with a drained battery led to unpleasant engine noise and annoyance. I wasn’t put-putting around though as a result. I wasn’t keeping track at all, but I’d estimate the battery went totally out of the picture about 2 hours into the day.

    Then again, I wasn’t tackling one big mountainside, I was driving in “foothill” territory with lots of elevation changes on roads where holding momentum is the point. On those roads 55mph is fast, in the Prius it was dangerous fast (that’s the real problem with the car). My milage however, sunk to the point where it was comparable to the Magnum R/T I was driving the day before (around 20mpg). I was driving the piss out of it to be fair, and before the battery went it did return good mpg.

    All of these points may not matter though, if the new one is as good as early reviewers claim. Then again, past Prius review gave good marks too.

    Diesel is better if you like driving.

  • avatar
    C. Alan

    I used to commute from Bakersfield CA, to Tehachapi CA in a 2000 Insight. That is about a 3600 foot climb spread over about 25 miles. In the case of my Insight, I would normally drain my battery about 1/3 the way up the hill, and the end result was alway me downshifting from 5th to 4th to maintain highway speeds.

    Was it terrible? No. My gas milage would drop from the high 50s into the 30s going up the hill. Given the fact that I could nearly coast all the way down the hill, my overall gas milage for that commute was about 60 mpg.

  • avatar
    brettc

    If you’re going to be driving in a lot of hilly highway terrain, that’s where a modern Turbodiesel excels. You might want to test drive a Jetta TDI and a Prius and see which one works better.

  • avatar
    psarhjinian

    The flip side of this is that the trip to work in the morning could/would be largely on battery power as the regenerative braking would come into play on much of the trip in. I think it’d be a wash in terms of economy.

    I’ve driven a Prius and an Escape with flat batteries. It’s not great, but it’s not bad, either. The Escape was marginally worse, but it was fully loaded with people and gear at the time.

  • avatar

    Thanks everyone. This was, btw, a hypothetical question. I’m not planning on buying a hybrid, and I don’t live in California, but I’ve been awfully curious about how bad a problem a hybrid would have in the mountains. And, FYI, that is (or was) my baby blue falcon, shot in ’71 or ’72 (after the cross country trip), which RF peeled off of my website, motorlegends.com.

  • avatar
    Robert Schwartz

    Bottom line: If you live north of 40 North or West of 100 West, Hybrids are not for you. But something else.

  • avatar
    galaxygreymx5

    I’ve had two hybrids and the short answer (in my opinion) is this:

    The Toyota system makes driving with a flat battery seamless (if noisy), the Honda not so much.

    Long Answer:

    I took my ’04 Prius from LA to Vegas in the middle of summer (110+ F) loaded with four people of generous proportion, A/C set at 72 F, cruise set at 85 MPH, and the speed never deviated from the setting, even when the battery was at one bar. Anyone who’s done this trip is aware of the massive hill climb involved. I achieved 48 MPG round trip.

    My Insight (first gen) did not handle a flat battery as gracefully as the Prius. It would try to force-charge at every opportunity, even if you were still demanding more power. Worse, as the car aged, the battery would “recalibrate” with no warning, leaving me with a drastic power loss at inopportune times.

    The Toyota setup seemed to do a very nice job of balancing out my power needs with the goal of economy, and never left me in a position of needing more speed. I could always stay in the fast lane, always pass other cars, although the little engine might be screaming to do it.

    I found the Honda’s IMA system frustrating and too simple for its own good, and it often left me wanting more power or not being able to keep up with fast traffic. Maybe it’s better with a CVT (mine was a 5-speed manual).

  • avatar
    Redbarchetta

    I wonder how the Volt will hold up in this situation. If it’s a 25 mile trip straight up will you be able to so all electric. When the engine kicks in on longer uphills will it be unbearably loud and slow.

    I still think the Volt concept needs a small 1 liter turbo diesel rather than a gas engine.

  • avatar

    buzzliteyear : The battery control electronics on hybrids keep the battery charged between about 15% and 85% of full charge no matter what.

    That’s what enables the battery packs to last 10 years/150k+ miles.

    Excessive battery pack wear is probably a non-issue in this situation.

    That’s a great point.

  • avatar
    T2

    How high could a Prius climb before the battery would run so low as to cease contributing to horsepower

    The best place to answer that is to look over at the john1701a.com website.

    It will depend on battery state of charge as the hill is encountered, total mass – accounting for passengers and luggage, and last but not least the gradient.
    To give you an idea of the battery energy. 1.3Kwhr could raise 2890lb to 600 feet. It’s immaterial since the car will not allow that order of total battery depletion to occur, as someone already pointed out.

    The battery will contribute 28Hp for about two minutes before you are reduced to just the basic engine power. The engine power depends on the roadspeed you are going. Here are some figures I computed that abide by the planetary gear ratio of Toyota’Hybrid Synergy drive on all ’04 to ’09 Prius.

    At 20mph 55Hp is available rising to 76Hp at 51mph. If you will excuse the Back to the Future similarity 51.28mph is quite an important point on the system power curve. It is the first time that the engine is able to reach its max rpm and therefore max power From this point to 100mph the engine remains at 5000rpm as long as the load is high enough to warrant 76Hp being drawn.

    I suspect the real problem is the driver backing off on the accelerator pedal when the engine starts to ‘get busy’. Lack of performance could be due to reticence on the part of the driver and nothing to do with the car at all. The engine may sound loud but the engine is well within its limits, and computer controlled against overspeed.

    The Echo, which I drive, has the same engine as the Prius but without the Atkinson camming. In the Echo the 1NZ-FE engine is rated at 108HP at 6000rpm. From the figures I gave at the beginning the Prius engine 1NZ-FXE is clearly operated safely, well under that rating. So let’er rip and then tell me there’s a ‘lack of power’ problem here.

    Meanwhile is anyone else having difficulty with “Chrysler Bankruptcy Analysis III” ?

  • avatar
    ajla

    If you want a hybrid, and you live in the mountains, does GM ever have a Tahoe hybrid for you.

  • avatar
    ttacgreg

    Redbarchetta . . .
    I would add that the altitude makes it worse
    at 9000 feet elevation, a non forced induction motor has only about 70% of sea level power. And I have to wonder how the cold affects the batteries too.

    I cannot remember the issue, but R&T did a Prius and original Insight hill climb years ago The first try with the 5-sp M Insight, they drove conventionally and it ran out of battery and limped to the top. They tried again, and obeyed the computer (the shift light) and even though the shifts were counterintuitive, the batteries maintained a better charge, and the car maintained its speed to the top.

  • avatar
    don1967

    Anybody with a tortuous commute like that who asks about Hybrid cars is not interested in gas consumption or the environment, so don’t waste your breath proposing “clean” diesels.

    These people are only interested in driving a fashion accessory which mitigates their inefficient lifestyle, which justifies driving a fashion accessory.

    Move closer to work, people, and drive whatever the hell you want.

  • avatar

    @Don1967
    I’m actually not in the market for a hybrid. I like my internal combustion straight, like my bourbon. I asked the question out of pure intellectual curiosity. But my guess is that a lot of non-car people who are not terribly scientifically literate, even if otherwise smart, and who live in mountainous conditions, might make the mistake of buying a hybrid, but would be perfectly happy to buy a clean diesel instead, if only they knew. Or a Fit.

  • avatar
    don1967

    Understood, David. I figured this was a hypothetical question, which is why I left my comments in the third person.

    It actually does make for an interesting technical discussion, but being outclassed by the B&B in this particular area I stick to the “big picture” perspective.

    It’s all good in the end… you can’t get this stuff over at Car & Sponsor.

  • avatar
    j_slez

    I made the decision to get a hybrid for a commute much like you describe – over 1000 feet of elevation change. In the downhill direction, nearly infinite gas mileage. Going up, it sucks, but it’s probably imperceptibly worse than a non-hybrid. On average, I’m pretty happy.

    And yes, going up the battery will get down to the minimum and the engine will do all the work, so then it’s your call on whether the engine has enough power to suit your needs. I’ve found that the Ford/Mazda 2.5L is strong enough for me.

  • avatar
    afuller

    Okay so the mountains I live in aren’t 10k feet high but we’re at a more manageable 6000 feet.

    My commute involves climbing about 1000 feet almost immdiately in the morning with then a nice easy downhill for about 6 miles followed by *fairly level* ground for the next 20 or so. My starting point is about 1000 feet above my finish point so we’ll call it a 2000 foot elevation change with the mountain in the middle.

    In my 2000 Insight I start off in the morning with about half a charge, at the base of the hill I just punch it and have found that I reach zero charge just as I reach the crest. I then basically coast the rest of the way to work and get a full charge by the time I’m there.

    On the way home I find that I can keep momentum up without being a rolling roadblock just fine until I hit the steep part of the hill again where I punch it and again run out of charge right before the peak. I gain about half my charge back before I turn into my driveway.

    Since I’ve got the 5-spd it’s simple to just downshift if necessary. I’ve burned out the charge before even reaching the bottom of the steep part and have been just fine downshifting a couple of times and still been able to maintain road speed (60mph) up the hill.

    Average mpg for the trip to work is 75, home is 80.

    I’ve found that by exercising the battery from full to empty in this matter has ceased all recalibrations.

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