Low MPG & Battery display always green.

Discussion in 'Gen 2 Prius Main Forum' started by rodri9o, Dec 27, 2018.

  1. rodri9o

    rodri9o Junior Member

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    Hi all.
    I don't post here much (this may well be my first one!) but I have used this site as a valuable resource in maintaining my 2006 Prius.

    All of the below driving was done at about 28-32 degrees F and the car has about 218,000 miles (Dec 2018). I bought it with 192,000 (Feb of 2018), and All I've done is oil changes, hybrid drive oil change, air and cabin air filters, PCV valve, new plugs, and a few LED bulbs, since the left rear tail light bulb went, so I replaced both with LED.

    Yesterday, while driving, I noticed that the battery display on the dash had all but one bar of charge and green. As I drove 10 min to my destination, the display showed a FULL set of bars, charged. I've seen the green bars -1 fairly often on my drives (80% commuting in HOV lane), but usually always would display as blue.

    An hour later, on commute to work, the battery display had the battery shown as fully green, -1 bar) for the duration my my 40 mile, mostly flat, commute. Also noticed that I was getting around 34-39mpg, where I usually get around 44-47.

    I did the 12v battery check and in accessory more, and with ignition mode battery never drops below 12V.

    I've also, in the last few days, have heard what I think is the hybrid cooling pump go after I shut the car off.

    The car displays no lights on dash other than the usual ones...only have the TPMS light warning, but that's been there since I got the car.

    This has been a great car and i'd love to see 300K on it....any advice to help resolve the above is greatly appreciated. :)
     
  2. bisco

    bisco cookie crumbler

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    12 volt should read at least 12.4 volts, or cca maybe low with a load on it.

    all green is unusual, maybe weak cells not discharging properly and assisting engine for better mpg's. you'd need tech stream to load test the cells.
    bad battery usually charges/discharges quickly.

    are you sure it isn't just colder than normal and reformulated gas affecting your mpg's?

    tires and pressures are often suspect with mpg's, as are rubbing brakes and e brake. air filter clean?

    not sure what the buzzing is after shutting down, coolant or brake accumulator?
     
  3. rodri9o

    rodri9o Junior Member

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    Thanks for the reply. When you say the battery should read 12.4 volts, is that where the car on, or with the ignition on and the engine running?

    I've scheduled an appointment with a Toyota dealer to have them check the Hybrid battery. If cells on the Hybrid battery are shot, would that not throw some kind of code and show a light on the dashboard?

    Thank you for your help
     
  4. bisco

    bisco cookie crumbler

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    car on, not ready.

    yes, you should get a red triangle when the cells go outside a predetermined parameter.
     
  5. PAUL SCHULTZ

    PAUL SCHULTZ Member

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    The pump sound after turning off the vehicle is likely the coolant being pumped into the thermal reservoir. It actually happens everytime the vehicle is shut off but you may not have noticed until now. It is basically a thermos style of reservoir to retain heat in the coolant so that the engine warms up a bit quicker on the next start-up.

    Paul.
     
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  6. edthefox5

    edthefox5 Senior Member

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    I have 2 easy tests for both the 12 volt battery and the hybrid battery:

    12 volt:
    With car off open hood and using a dc voltmeter measure the dc voltage at the front 12 volt battery jump point. Write that down.
    With car still off turn on the headlights put them on high beam and let them run for 5 minutes with car off.
    At the end of 5 minutes with the high beams still on and car off measure the dc voltage at the front jump point. Post those 2 measurements.
    On my 3 years old Optima yellowtop I see no voltage drop in this test. A tired battery will show significant voltage drop.

    Hybrid battery:
    With tires properly inflated to 38 lbs all around find a nice flat stretch of road a few miles long. With ac off and lights offs get up to 55 miles an hour and engage cruise control. Reset the mileage meter button on the MFD screen.With car at 55 miles an hour drive for a few miles on CC. At the end of those few miles what does the mileage read on the mfd? Should be at least 55 mpg's.
     
  7. rodri9o

    rodri9o Junior Member

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    edthefox5: I will do this this weekend and report back. In driving to work today, with what most people consider flat roads, I was running the vehicle signal display and the battery was always at 14v. Sometimes getting to 14.2, with a drop to 13.9 about 3 times in 10 minutes' worth of driving at 40-70, navigating traffic lights and highway. Defroster was on, AC, headlights, both wipers going...
     
    #7 rodri9o, Dec 28, 2018
    Last edited: Dec 28, 2018
  8. rodri9o

    rodri9o Junior Member

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    Ok...so if I don't have the red triangle showing, and the batteries are within that parameter, it is probably not worth taking to Toyota for the hybrid battery test, is it?
     
  9. rodri9o

    rodri9o Junior Member

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    I've noticed the noise that pump makes...and what I think is the brake pressure pump as well. Yesterday was a bit of a cold day and I didn't hear it, but then again I did do a lot of small drives and all those drives were within a close time-span. I just heard it upon getting to work. I may replace it when the weather gets warmer up here in the Northeast. Seems a fairly simple repalcement, and after researching the Toyota service records, it was replaced at IIRC) +/- 60k...likely that recall/TSB
     
  10. bisco

    bisco cookie crumbler

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    i wouldn't take it to the dealer until you have exhausted all the possibilities here.
     
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  11. jerrymildred

    jerrymildred Senior Member

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    This simply means the 12V charging system is properly charging the 12V battery.

    One possible and very simple explanation for both the green bars and the poor fuel economy is the short trips you mentioned. Especially in cold weather. The engine takes longer to warm up in the cold. If the engine is using more power than it needs for propulsion as the computers keep it at an efficient rpm, that extra power goes to the battery so you can use it later. But, if you get to your destination before you get the charge used up, it will accumulate. It's an amazing machine!
     
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  12. rodri9o

    rodri9o Junior Member

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    yeah...I hear ya. I'll cancel that appt. now.
     
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  13. rodri9o

    rodri9o Junior Member

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    I get it. That IS pretty smart. However, I get the poor mileage and green bars on trips that are long AND short.

    Funnily enough...last night I sat int he car on the phone while it was idling...and the bars dropped to blue...and to 5, which seemed normal. Then, on commute this morning, it gradually went to green again (1 bar below max) and stayed there for the last 10 min of my 45 min commute....mileage does seem better.

    I will test as per Bisco's suggestions...but maybe I really did just go through a really really cold day where I didn't warm up the car, but I've never noticed the bars being green for THAT long....

    Will report back with test results.

    Can't thank you all enough for the help. Want to get this sucker to 300K!
     
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  14. bisco

    bisco cookie crumbler

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    best thing you can do is track manual fill up mpg's at the pump, and try to ignore short term mpg's. when you see a disturbing trend, then it's time to take action.
     
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  15. Skibob

    Skibob Senior Member

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    2 things I can think of. Your AC pump runs less in the winter, especially places where the humidity is low in the winter, like New York. Prius tends to run more in the green in the winter because of that, it’s not abnormal.
    Secondly all cars get lower mileage in cold temps, you see more of it in a Prius because the warm weather mileage is so high.
    Also do they change the formulation of gas in your area? Adding more methanol to the winter fuel would reduce mileage.
     
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  16. rodri9o

    rodri9o Junior Member

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    Yeah...I normally use the cars system but once in a while I'll whip the calculator out.
     
  17. rodri9o

    rodri9o Junior Member

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    Skibob:
    They do change the formulation on gasoline here for the winter. I noticed that drop some weeks back as well. Suddedly 48mpg was not possible. 45 was more attainable.
     
  18. edthefox5

    edthefox5 Senior Member

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    As I said 4 times in my post the 12 volt test should be done with the CAR OFF.
     
    #18 edthefox5, Dec 28, 2018
    Last edited: Dec 28, 2018
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  19. bisco

    bisco cookie crumbler

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    and that requires a volt meter
     
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  20. rodri9o

    rodri9o Junior Member

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    I get it. I was explaining what I noticed while driving the car.

    I can't use the voltmeter, with hood open while driving car.
     
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