Engine (almost) always running

Discussion in 'Gen 2 Prius Main Forum' started by Ed Ferris, Jun 28, 2019.

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  1. Ed Ferris

    Ed Ferris Junior Member

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    I recently bought a 2007 Prius with very high miles. The main battery seems to be in good shape, in that it goes from 2 to 7 bars and usually is at 6. However, it very rarely runs on the battery only, and then only at walking speeds. Even after I drove it on the highway for an hour, the engine would be on at 20-30 mph on city streets. The fuel economy is also disappointing, around 34 mpg according to the Consumption screen. But no warning lights are on, after I had the cat. converter replaced. I'm not using AC or the fan.
    So, is the car supposed to operate as an EV up to medium speeds?
     
    #1 Ed Ferris, Jun 28, 2019
  2. cthindi

    cthindi Member

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    Car can operate as EV at any speed. Except at speeds greater than 42 or so, engine had to run to protect MG1. It could just run without using any fuel.

    Once the coolant temp is in operating range, engine should get off frequently at speeds like 20-30 mph. Fuel efficiency of 34 is definitely not right, unless all you trips are short like a 2-3 miles.

    I am getting in northeast 47 summer and 40 winter. It has dropped from what used to be 50/45.
     
    #2 cthindi, Jun 28, 2019
  3. bisco

    bisco cookie crumbler

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    congrats and welcome!

    what are you checking codes with?

    how is the 12v health?

    is it the original hv battery?
     
    #3 bisco, Jun 28, 2019
  4. kenoarto

    kenoarto Senior Member

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    Welcome to PriusChat!
    No the car does NOT operate as an EV up to medium speeds.
    There's lot's of info on expected mpg here. Suggest you start by doing a search for "pulse and glide".
     
    #4 kenoarto, Jun 28, 2019
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  5. Ed Ferris

    Ed Ferris Junior Member

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    Thanks for the welcome.
    To answer Bisco's questions:
    I bought a $20 code reader at Walmart. Yes, I know it's ridiculously cheap, but it does show the P-codes.
    I had the 12v battery replaced. The independent mechanic who did it gets his batteries from Interstate, so I got stuck with an expensive Optima yellow-top. It shows 12.3v after sitting overnight, which is acceptable but not good, so I gather.
    Yes, the hybrid battery has a Toyota label on it, so it probably is original. However, this was courier car with fleet maintenance, so there is a chance it is the second genuine Toyota battery in the car.
    I have been looking at the posts on expected mpg. What I still didn't get is whether the car should be driving on the battery only at low speeds. Apparently not. Actually, 34 mpg is fine by me; I just want to avoid imminent problems. But the computer should tell me about them, shouldn't it?
     
    #5 Ed Ferris, Jun 29, 2019
  6. bisco

    bisco cookie crumbler

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    i'm not sure it is even acceptable. it depends on what happens when a load is put on it, and how many volts the computers are receiving.
    that being said, at 12.3, the engine is surely running somewhat more to recharge the hybrid battery which is trying to recharge the 12v.
    is it the cause of your role? idk, but you have to start with the basics. i would buy an appropriate age charger, or take it somewhere to have it recharged.
    a new 12v agm should hold in the high 12's. if not, there is a parasitic drain with the car off, or the battery is kaput
     
    #6 bisco, Jun 29, 2019
  7. bisco

    bisco cookie crumbler

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    some problems are not detected by the computer systems. or not until they fail. plugs, injectors, throttle body, maf sensor, etc. can all be dirty and cause poor mpg without throwing a troublecode.
     
    #7 bisco, Jun 29, 2019
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  8. edthefox5

    edthefox5 Senior Member

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    Forget about ev the car really doesn’t do that well and there’s nothing free.
    It’s not an electric car, If you are able to ev at all the hybrid battery needs to be charged back up and that costs gas. So ev does nothing for you.
    Haven’t heard the term ev on here for a long time as it’s a moot point,

    If your only able to get 34 mpgs the hybrid battery is in early stage of failure.

    It has not thrown a code yet so it’s able to be rejuvenated. Lots of us use a Prolong hybrid battery charger/discharger from hybridautomotive.com if done correctly can get you another 2+ years out of the hybrid battery. I’m on my 18 month with mine running good.

    Use the search forum button up top and search

    Prolong
     
    #8 edthefox5, Jun 29, 2019
  9. kenoarto

    kenoarto Senior Member

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    C'mon !!! 34 mpg is common if used for short trips to local stores. No proven reason to buy a time consuming $700 charger that can destroy a good battery if used too fast.

    Posted via the PriusChat mobile app.
     
    #9 kenoarto, Jun 29, 2019
  10. George W

    George W Senior Member

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    I bought a new 12V battery which turned out to be under charged from the store. Contrary to what some say, my Gen2 did not bring it up to full charge. After being topped off (before being put back in the car), it now holds 13.1 from overnight, onsistently.
     
    #10 George W, Jun 29, 2019
  11. kenoarto

    kenoarto Senior Member

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    $700 Prolong charger is for the big HV battery.

    Posted via the PriusChat mobile app.
     
    #11 kenoarto, Jun 29, 2019
  12. Ed Ferris

    Ed Ferris Junior Member

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    Well, the local specialist advertises a "hybrid battery repair" for $900, and the Prolong kit costs $700, so I think I'll take the one with the warranty, if I have to. After taking the car out for a highway trip, the aux. battery reading was 13.9 volts! Now, that's not possible for a 6-cell lead-acid. I'll check it again tomorrow morning.
    And, yes, the Consumption screen did show 34 mpg for the highway trip. Apparently the trip out was downhill because I got 52-mpg bars, but the return made up for it.
     
    #12 Ed Ferris, Jun 29, 2019
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  13. George W

    George W Senior Member

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    All I am saying, is that having a new 12 volt battery doesn't guarantee that it was given over-the-counter fully charged. My Gen2 ran with this battery in the car for a week, did not increase its resting voltage 1iota. After pulling it and using a smart charger (CTEK MUS 4.3), I brought the resting voltage up to the proper number so that the Prius' trickle charge can maintain it.
     
    #13 George W, Jun 29, 2019
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  14. edthefox5

    edthefox5 Senior Member

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    It will read that if the car is running that’s the charging voltage. But a healthy sitting battery in my Prius measures 12.6 volts.

    Here’s a definitive simple test. With car off measure battery voltage at the front jump point.
    Write that down. Then with car off turn on headlights in high beam and leave them on for 5 minutes.
    With headLights on at the end of 5 minutes measure the voltage.
    Then turn headlights off and with car still off measure battery voltage.

    What are those 3 voltages?
     
    #14 edthefox5, Jun 30, 2019
    Last edited: Jun 30, 2019
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  15. edthefox5

    edthefox5 Senior Member

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    Why are you pulling the battery? Just hook the charger to the front jump points that’s why they are there.
     
    #15 edthefox5, Jun 30, 2019
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  16. kenoarto

    kenoarto Senior Member

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    1) Calculate your mpg after the use of two full gas tanks. 2) 12v battery voltage should be measured cold, in the morning, after a full night's rest, not running. It should measure 14.1 while running. 3) $900 HV battery "repairs" do not last long. Better to spend $1600 on an all new one ... when the time comes.

    Posted via the PriusChat mobile app.
     
    #16 kenoarto, Jun 30, 2019
  17. George W

    George W Senior Member

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    13 ft of copper adds resistance
     
    #17 George W, Jun 30, 2019
  18. kenoarto

    kenoarto Senior Member

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    One hour isn't nearly long enough. Think 6 to 6 hours for a full charge.

    Posted via the PriusChat mobile app.
     
    #18 kenoarto, Jun 30, 2019
  19. Ed Ferris

    Ed Ferris Junior Member

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    As for the 12v battery, I did the high-beam test and got 12.6, 12.2, and 12.5 volts, measured with a VOM at the battery. So I think George W is right and the battery was not fully charged when installed. Can it be charged in the car, using the jump points? I don't want to fry the electronics if the charger gets a transient. Probably a better idea to unbolt the terminals and charge it in the trunk.
    Isn't it insane that there is an electrical device bolted to the battery positive strap?
    Should the hybrid battery be going from six to five or four bars in short (2 mile) city trips at 30-40 mph? I now find it is uphill to the grocery store, from the way the Energy screen shows the charge.
     
    #19 Ed Ferris, Jun 30, 2019
  20. bisco

    bisco cookie crumbler

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    yes, you can use the jump point, that's why its there.

    no, it is not insane.

    yes it is normal for the hybrid battery to go up and down. a lot.
     
    #20 bisco, Jun 30, 2019
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