Hill Performance 2008 Prius

I'm not sure why that's happening to ya but, I'll try to give you some info. First off, how far away is this hill? Does the ICE have time to heat up b4 u get there? If not, I would say that is part of the reason. If the ICE is not warmed up to 110 F, the system tries to use nearly all battery for propulsion. If that's not the case, I can't offer another explanation to you but, you can always just anticipate the hill and floor the accelerator prior to starting up the hill. I have not had any issues similiar to this. I do agree with the dealer in that there is nothing wrong w/ the car. I would however, tell you to check the oil to see if its too full (some dealers will overfill the oil on this car resulting in lower power).

As far as the green bars go, green bars should and will be a rare occurence. The system is designed to keep the charge around 60% (5-6 blue bars). The only way you will get a green bar is to go 41-43 mph for a long distance (for some reason this always gives me a green bar charge) or go down a long hill using regen for a majority of the descent.

I don't know where you live but, I hope your disappointment will wane once you start to realize the money you save at the pump. In all honesty, the Prius does not like 75mph and going that speed consistently will almost always result in a low charge (it takes ICE and electric power to maintain 75mph). I would suggest 65-68 mph but if that's too slow, I would say 72 max. This is just my advice but I find the car is much happier at <70 mph than 73+. It can go 75+ all day long but it is happier below 73. These are just my observations. Standing by for divergent opinions.

 

Yeah, that's really weird. I wish I had a better answer 4 ya but, unfortunately, I don't.

 

A) Yes the ICE will be warm. You should be in stage 4 by then. Do you have any opportunities to let the engine stop fully before getting on the highway? Like waiting to turn onto an on-ramp or anything? You should feel the engine completely stop at least once before you get on the highway and after it has been running for a minute. This will ensure you are in stage 4 and making use of the full gas engine.

B) So you have tiny hills. What is the elevation change?

C) The car will behave differently all the time because the power available is dependant on so many factors. In a big V8 there is so much wasted power just there all the time, that the extra draw from running the AC on high or by constantly re-adjusting the pedal is barely noticed. In the Prius you have enough power, but you can't be silly about it. I routinely drive up and down I-70 through Colorado where the grades are 7% or more. Speed limit is 55mph to 65mph but the actual road speed is closer to 80mph - 85mph throughout the whole thing with the exceptions of the tunnels. Up thousands of feet, and down thousands of feet, up thousands of feet, and down thousands of feet. My 2006 Prius does just fine cruising up the grade at 80mph. Push the pedal to the power level you want and stay there. Don't use cruise control as it will speed up and slow down a bunch over the hill. This is all potentially wasted power and could be effecting what you see. If you start with a green battery (abnormal in the first place) the extra waste may bring you down to 2 bars or so but you still have all the power. If you start with 5 bars which is more normal the same waste will peg you at 2 bars and 1 bar and limit your available power.

 

If it stops just once, then no problem there. Good to know!

A short hill at 80mph could very well drain the battery if a lot of speed modulation is being done. Next time jam the pedal to the position you want and keep it there. If you go too fast for your liking slow down not by pulling full off or braking, but by releasing the accelerator a tiny bit. If you go too slowly, mash the pedal for the engine revs then back off slowly to where the engine keeps high rpm but less electric if you really want to maximize fuel consumption (note, not efficiency) and increase performance.

You will find with the Prius that every little thing is more noticeable. Partly because of all the instant feedback it gives you and partly because you just pay more attention. If you drive the same route every day things like wind direction and speed, moisture on the roads, traffic congestion, tire PSI, temperature, and more all effect mileage. A 100mpg trip one day might be 40mpg the next. 3 weeks, or 15 days commute (assumption based on a 5 day work week and a single commute a day) is too small of a sample set to make any generalizations. And everything is connected. If it is colder outside, your tire pressure is lower, your fuel economy will be lower, the engine and battery work harder to move the car. And then you probably want heat, so you take heat from the engine to warm the cabin, which means the engine has to run more just to make heat. Or if the temperature is high, and you run the AC you drain the battery quickly or might drive with the windows down, or the battery just might be too hot to function and protect itself by limiting output power, or or or or, just so many variables.

Even the length of time you spent stopped at a stop light with parasitic drain on the battery will be different.

With highway driving it is really easy to fully deplete the battery and harder to fill it back up. Note that as mentioned previous, a happy battery is a blue battery. A too charged battery is a green battery. A too depleted battery is a 1-bar (argument over pink versus purple exist, so 1-bar is common terminology). Note that when all bars are full and green, the battery is actually at 80% full. When only 1 pink/purple bar exists, the battery is actually at 40% full. This maximizes the life.

And really the cycling of the battery is normal and what acts as a power buffer netting better mileage overall. So don't be afraid of SOC (State of Charge) swings, it is normal.

I would be willing to bet over your 3 weeks, something changed. Traffic patter, temperature, or even the state of charge before you left the house or got on the highway or something. All that has an effect.

 

Here's something for you to try. Switch to "Energy" screen and monitor SOC. Keep the car at 65-68 for about 2-3 miles prior to the subject hill. This should allow your battery to obtain 5-6 (hopefully 6) blue bars prior to starting up the hill. Just prior to reaching the hill, set your cruise to 75 (stay on "Energy" screen). See if the car will carry you up the hill @ 75. Report the following back to us.
1) What was your SOC prior to going up the hill (how many bars)?
2) What was your SOC when you reached the top of the hill?
3) Did the car maintain speed?
4) If it didn't, at what SOC did you begin to lose speed?

My guess is that for the first 3 weeks you started up the hill with a full (6bar) SOC. On the 4th week (and thereafter) you started up the hill w/ 4 bars or less and the hybrid system (HSD) acted to protect the battery pack (one or two bars of SOC). This does not indicate a problem but it does indicate the HSD is acting appropriately.

 

Well as stated b4, numerous factors could have influenced that.

 

45 minutes at 5 mph will drain the hybrid battery, so that time you would be mostly ice power which might result in it being unable to hold the speed. but the battery should recharge in subsequent driving. is it usually arounf the middle, 5-6 bars? you may also want to have the 12v tested, if it's weak, it puts a constant drain on the hybrid battery. colder weather also taxes the hybrid battery a bit more. all the best!

 

My Prius power at the wheels, over time, is not linear Ive noticed.

Some days depending on ambient temperature, temperature of the ICE, what I have in the car (passengers, etc), it accelerates differently than the day before. I expect this but it did alarm me one day when it seemed particularly gutless.

Im still getting 47.5mpg so Im not complaining

To the OP, a few questions that could possibly affect performance:
- You mentioned its gotten colder where you live (but I dont know where because you didnt fill it out in your profile!!). Have you checked your tire pressures? This can create drag.

- How many miles on your 2008?
-ii What condition is your 12v battery in? If its low/bad, your traction battery will be busy charging it all the time.

- Have you checked your oil level and air filter lately on your ICE? This can affect the performance of the ICE.

- Could it possibly be the switch between summer and winter blend fuels?
-ii Suggest you run a bottle of Techron through the tank, if you havent already

- Any additional weight in the car that wasnt in there before?

Just a few suggestions to check first before panicking. I bought my car in September when it was still warm. I got used to it changing behaviors as the weather shifted towards colder. I installed a block heater in October that I keep on a timer now that significantly aids in warm up too.