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Acceleration problem up long hills

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Smardaz, Jun 18, 2014.

  1. Smardaz

    Smardaz Junior Member

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    2008 Prius:A few weeks ago I was making one of my regular trips over to Eastern Washington. As I was going up Snoqualmie Pass in the eastbound direction I noticed my car was not holding the cruise speed I had set it at. I always set it around 72-73 mph. I noticed it had dropped to 65, I turned off the cruise and tried to accelerate but it would go not faster. I let off the pedal and dropped to 55 and again tried to accelerate but it would not. I got to the top of the pass and pulled off the hwy. I parked and turned off the car and turned it back on and it behaved normally the rest of the trip. It did not happen on the way back however it may be worth noting the it's a much shorter hill to the summit going westbound then it is going east.
    Yesterday I was making the trip again and the same thing happened going up the long eastbound hill. This time I looked at the trip info screen and noticed the battery was completely drained but I didn't know if that was normal on a hill as I've never really paid attention to it before. I looked at the maint screen today and the battery sits at 12.4 with no load and 14.3 or so when the engine is running.
    Anyone have any ideas where to go from here?
     
  2. tanglefoot

    tanglefoot Whee!

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    This is normal operation of the hybrid system once the traction battery reaches minimum charge (~40%, 1 purple bar on the battery meter on the energy flow screen) and the electric drive stops assisting. There's likely nothing wrong with the car.

    On long climbs, it's common for the traction battery to reach minimum charge. The gasoline engine does not have much horsepower or torque on its own, without the help of the electric drive, so the car becomes quite lethargic at this stage until the grade lessens and the traction battery is able to recharge again.

    It sounds like this is the first time you have experienced this. It may be that the state of charge of the traction battery just happened to be lower than normal before the start of the climb, so it reached minimum before cresting the hill.

    There are different thoughts of how to reach the top of climbs without the electric drive cutting out. One is to approach the bottom of the hill with quite a bit of speed and let the speed gradually decrease as you reach the top. If the climb is long and steep enough, there may be no practical way to crest it with charge remaining...just limp over the top on the gasoline engine (I try to keep it below an estimated 4000 rpm to reduce engine wear--I don't like to let it scream) and then recharge on the way down.
     
    #2 tanglefoot, Jun 18, 2014
    Last edited: Jun 18, 2014
  3. Smardaz

    Smardaz Junior Member

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    Thanks for the reassuring statement that there is nothing wrong with the car. It is, however, strange to me that in almost 6 years of driving this car and making this trip an average of 32 times a year, this is the first time it has happened.
     
  4. tanglefoot

    tanglefoot Whee!

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    I edited to "There is LIKELY nothing wrong with the car." after you quoted it. How many miles are on the car? It's possible that the traction pack is losing some capacity. See if it becomes a habit for it to go to minimum on your next trips over this hill. If it only happened this one time, it's probably just a chance thing that the charge level happened to be lower before you started climbing.

    You might monitor the charge level on the energy flow screen more diligently and make note of the level when you get to the hill, how quickly it depletes as you climb, and how the charge level changes in other driving.

    I like the screenname. It reminds me of the credits on Car Talk. I'd probably be Major Payne Diaz.
     
  5. Smardaz

    Smardaz Junior Member

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    LOL, thanks. Actually it happened twice. There is just over 185,000 miles on the car. I've not been easy on it, it's been great so far. This is just a little concerning as we are making a drive to SoCal in July and I want to make sure there are no hiccups.
     
  6. tanglefoot

    tanglefoot Whee!

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    With that odometer reading, it's possible that the traction pack is losing some capacity. It may not be close to failure though--you might be just fine for that road trip.

    Also pay attention to the sound of the traction pack cooling fan. It runs at high speed when the pack is under stress. The vent is located high on the passenger side, rear seat bolster. It helps to have a rear seat passenger listen for it, but when it's really churning, you can hear it from the front seats.

    Here in Colorado, just about every trip over the mountains depletes the traction battery, regardless of route or technique but I think some give it more pedal than others once the electric drive cuts out. I take it pretty slow but there are definitely Pri drivers that fly over the passes. Maybe they get to the top so fast, the traction battery doesn't have the TIME to deplete. :) I don't know which way is best.
     
  7. fuzzy1

    fuzzy1 Senior Member

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    Snoqualmie Pass has both a shallower slope, and much lower elevation (i.e. high barometric pressure and better ICE power), than the Colorado mountain roads. I hope other Washington GenII drivers chime in, but I'm not aware of them having the same problem with limited power and speed on Snoqualmie that some GenII owners report for I-70 in Colorado.
     
  8. edthefox5

    edthefox5 Senior Member

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    What is the car's maintenance? What have you done to the car so far? Last time you changed the Inverter coolant, trans fluid etc?
     
  9. nh7o

    nh7o Off grid since 1980

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    185,000 miles on mountain roads...yes, you can be certain the traction battery has reduced capacity by now. The behavior you see is normal for that level of use.
     
  10. Easy Rider

    Easy Rider Active Member

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    With that odometer reading it is also highy likely that the ICE has lost some of it's capacity too. Using a bit more oil than it used to ? Put new plugs in it lately, air filter, put Techron in the gas ? It might just be getting old but neglecting needed routine maintenance can make matters even worse.
     
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    When was the last time that the engine air filter was changed? I suggest you remove the filter, inspect it (the bottom side is the side that collects dirt) and replace as needed.