MPG on highway

Discussion in 'Gen 2 Prius Fuel Economy' started by Jum, Feb 19, 2018.

  1. srellim234

    srellim234 Senior Member

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    It's obviously clear you are unfamiliar with all conditions and every Prius on the road.
     
  2. stylinnnn

    stylinnnn New Member

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    For a short distance yes, but never for a long distance.
     
  3. bisco

    bisco cookie crumbler

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    mt everest?
     
  4. JimboPalmer

    JimboPalmer Friend to those who want no friends

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    I drove 300 miles home in 8 inches of snow at 20 F and got 32 MPG, and am not ashamed of it
     
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  5. srellim234

    srellim234 Senior Member

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    Use a Prius for short hops all the time and you're going to average in the 30s. The car never gets time to properly warm up and shut off the gas engine for any decent period of time. I've had many tanks in the 30s that way. Use the car for newspaper delivery. Tow a trailer. Then come back and explain to us how you achieved over 40mpg with it since no one else has under those conditions.
     
  6. Mikesvagen

    Mikesvagen Junior Member

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    Replace the 12v battery there is no good reason for the 11.9V reading even under load. Sometimes being cheap will cost you more money. The 12V battery along with wipers, brakes, bulbs, tires and the like are wearable items that will require replacement at a point. You have an obvious problem why not just address it?
     
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  7. Jum

    Jum New Member

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    Yes, that's what I am going to do now. I wanted to see if the low mileage came from combination of cold, bad weather, steep roads, short trips. Now the temperature finally came above the 60s, and I get around 38/39 MPG so clearly there's something wrong. Part of it is also the blind trust in the garage that sold me the car, telling me that everything's fine.
     
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  8. Mikesvagen

    Mikesvagen Junior Member

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    Sorry if I came off harsh... A resting 12V battery should be at 12.6V. You will hear and see others dispute the number but a battery resting under 12.6V has already started to degrade...Are we talking a junk battery? No, but on the downside of its life cycle. 11.9V is a bad battery and as sensitive as our electrical systems are you will want to eliminate any weak links right from the start.
     
  9. dolj

    dolj Senior Member

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    Not meaning to be argumentative, but ...
    ... or more. A good OEM AGM 12 V battery should be 13.2 V when new and fully charged.
    This is true, but does not make the battery bad or terminal. If this is the open voltage after charging (with a modern automatic 12 V battery charge/maintaner with an AGM setting) to full and left to rest for 2 hours, you may be right if the resting voltage is 12.6 V or less. But without further diagnosis and testing, it isn't really possible to make any declaration about the battery's health.
    This is often stated here and other places, but no one to date has actually supplied any evidence to support the claim. Neither has anybody provided any information from the repair manual where it states 11.9 V as a critical pass/fail voltage.

    What I have seen personally and also read in the repair manual is somewhere in the 10 V or less territory and only some ECUs will have a problem at this voltage. Others will complain at much lower voltage.

    As the OEM 12 V battery is a relatively costly item, it is irresponsible to insist that someone immediately change out their 12 V battery just because a voltage reading of 11.8 or 11.9 V is quoted, especially if this is while under load.

    All 11.9 V (open voltage) says to me is that the battery is flat and needs to be charged up. If the 11.9 V is while under load, all that says to me is that battery is low and needs to be charged up. It is what happens, and what further diagnostics reveal, after charging.

    A questionable 12 V battery and 12 V supply problems are not the same thing and people here (and other places) need to stop linking them automatically. There may be a link, but equally there may not me. Proper diagnostic precess needs to separate these things and diagnose individually, while keeping track of the big picture.

    To add weight to what I am saying, here is just one real life example.

    DTC P1241 (among others) was set. Many here will jump on this as proof that the 12 V battery was bad. However, this is not so as the car was running at the time the code set, so 12 V supply was supplied by the inverter. Or not as in this case, which caused the 12 V supply to come solely from 12 V battery and as it was not being charged, it eventually dropped to the B+ threshold of P1241.

    Further, as the car was 1.5 hours away, I could not get to it and I advised, as the car exhibited no drivability issues, that the driver could continue the journey, but to drive it cautiously. During the remainder of the drive the car was subsequently cycle on/off 3 times and on the third time all the warning lights went off. By the time I was able to read the codes there were three, all current: B1421 (Air Conditioner), C1241 (ABS/VSC//TRAC) and P0A08 (Hybrid Control).

    B1421 was nothing to worry about as the car was read in the evening, so correctly told me there was no direct/bright sunlight.

    The real code here is the P0A08, which also explains the C1241.

    One of the first things to do in the work up for the P0A08 was to clear the codes (I saved the diagnostic before) and then check the 12 V battery and connections. These checked out ok. The battery voltage was around 12.9 V, all connections were clean and tight. No fault was found in checking the remaining steps in the diagnostic tree. The fault remains "inconclusive" as the code has not returned, so far (6 weeks later). I do expect that it will fault again in the future. I do not want to hijack this thread with people trying to diagnose this fault, as I have already done all that can be done, but, as I said above, I just give this as one example of how following a objective logical procedure avoids leaping to conclusion not supported by evidence.

    The real point to make is that a simple voltage reading on a battery does not tell you much. Codes are king, and following the diagnostic tree is a close second. Parroting what you read on PriusChat or elsewhere can have value, as long as you can be sure those saying it have credibility. As you may know from previous discussions, I place high value in the information posted by those that have hands on fixing the Gen 2 Prius. Even better when the info is supported by reliable (read base on the repair manual) data.

    Incidentally, the 12 V battery on the car continues to perform well and always has a high state of charge in the region of 12.9 V (after standing voltage is allowed to bleed off).
     
    #29 dolj, Mar 14, 2018
    Last edited: Mar 14, 2018
  10. Mikesvagen

    Mikesvagen Junior Member

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    The age of the battery is unknown, the vehicle was wrecked and repaired. How long did it sit in auction then repair facility? How many times has the battery been cycled down and charged.
    You are correct the proper diagnostic path has not been followed. Given the known history of this vehicle. I would stand by the 12v battery being bad.

    Charge the battery and check it with a hydrometer, usually if the battery is bad one or more cells will be drastically different than the others. If that is the case, recycle the battery, it is no longer usefull. If it is only slightly different you might try an equalization charge.
     
  11. Jum

    Jum New Member

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    Well, I think I have the answer now. I left the car for 10 days for a trip to europe, this morning the car started right up and was fine for my 60 mile commute (except I got 36 MPG average on this trip), but 3 hours late the car died right off after pressing start, dead battery, impossible to do anything.

    I got an optima battery, the car is now back on the road, I'll see if the mileage improves.

    Now there's something weird, the battery I had had large terminals, the optima has thinner terminals, and I can't fit the negative one even with shims. Would this be the item I need to fit it? Are there equivalent ones on amazon?
    Installation Kit for Optima battery in Prius

    Thanks
     
  12. bisco

    bisco cookie crumbler

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    i think you got the wrong battery, but the adapters may work, i'm not sure.
     
  13. Jum

    Jum New Member

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  14. bisco

    bisco cookie crumbler

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    when optima started making prius batteries back in the day, they only made one post size, and everyone had to buy adapters. after awhile, and enough complaints, they finally came out with the correct post size.
    i would give them a call.
     
  15. JimboPalmer

    JimboPalmer Friend to those who want no friends

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  16. Jum

    Jum New Member

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    I guess that's what happened. The battery was a Toyota, but it was not attached, and the vent plug was not connected.

    The current setup is attached
     

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  17. MelonPrius

    MelonPrius Active Member

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    I am on the original 12v for my '14 Prius, so I'm anticipating having to replace it this summer.

    I'm a bit confused...if I purchase an Optima 12v battery, does that mean I need to purchase additional accessories/cables? Or does this just apply to the gen 1 Prius?
     
  18. JimboPalmer

    JimboPalmer Friend to those who want no friends

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    If you buy the DS46B24R, it is a direct fit for gen 2, 3, and v. If you get a D51R, it will have the larger posts and needs adapters for gen 2, 3, and v.
     
  19. 05PreeUs

    05PreeUs Active Member

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    The "Lie-O-Meters" on these cars are notoriously error-ridden and should never be used to gauge actual fuel efficiency.
     
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