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Does hypermiling put too much strain on the 12V battery?

Discussion in 'Gen 3 Prius Fuel Economy' started by AZGeek, May 31, 2017.

  1. AZGeek

    AZGeek Semi-informed Member

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    My apologies to the group for not posting in quite some time. I've been happily enjoying my 2012 Model Five. I was always trying to maximize fuel economy on my Gen 2 but was over and done with that when I got my Gen 3.

    I just got done with a hypermiling stint on a tank and did fairly well, filling up at 700.1 total miles with 10.958 gallons (after the third click --- I was expecting to be on fumes and didn't believe the auto shut off on the nozzle). Display read 67.1 mpg and the actual turned out to be 63.9 from the total fill-up (or 65.1 after the first nozzle shut off).

    My battery problem started this morning when the car wouldn't turn on (everything was dead except for a very faint pulsing glow of the check engine light). I figured it was the battery and was going to take another vehicle but the display came to life and then I was able to start the car. I had about 670 miles on the tank by then. So I drove into work and hoped I could get it to start up again later in the day. No luck with that and used a coworker's battery jump (I didn't have his truck running and just jumpered to his battery). Everything came on as usual and the car started just fine.

    But this all has me wondering if all the fuel economy tactics (no hard acceleration, lots of pulsing, electric as much as possible, maximized braking time, etc.) meant that there just wasn't sufficient charging from the alternator to keep the 12V charged. I always keep the running lights and DTR lights lit, so I'm thinking that might has created more demand on the 12V.

    I know I'm crazy (but won't be doing the hypermiling stuff again because it just wasn't that much fun), but is it possible that my little uber economy gig was enough to do the battery in?

    Some details:
    Odo = 41,000 miles
    Original 12V battery
    Most miles in Tucson (and it's been fairly hot here during this tank of miles)
    (other mods listed in the signature line)
     
    #1 AZGeek, May 31, 2017
    Last edited: Jun 1, 2017
  2. JC91006

    JC91006 Senior Member

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    I think you have a dead 12v battery, nothing more.

    You should also not push your luck with the gas. Running out of gas can be hard on the cars battery and other components
     
    #2 JC91006, Jun 1, 2017
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  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Any time you are in Ready, the 12 volt battery is being charged, hypermileing or not.

    As with any car, a 5 year old 12 volt battery is near end of average life.

    The Truestart battery at your local dealer has an 84 month prorated warranty.

    amazon.com/ACDelco-ACDB24R-Advantage-Automotive-Battery/dp/B010GKJ8F6
     
    #3 JimboPalmer, Jun 1, 2017
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  4. fuzzy1

    fuzzy1 Senior Member

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    A Prius doesn't even have an alternator, so that cannot be the problem.

    12V battery charging goes direct from the traction battery, through an inverter, to the 12V bus all the time that the car is 'READY'. ICE On/Off has no impact on charging voltage or rate whatsoever. If you don't believe that, get a voltmeter or OBDII engine monitor (I have a ScanGauge, but there are many other more modern choices) to monitor it for yourself.

    As others have pointed out, it is more likely that your 12V is reaching the end of its life.
     
    #4 fuzzy1, Jun 1, 2017
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  5. bisco

    bisco cookie crumbler

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    plus, arizona is one of the anti battery states.:cool:
     
    #5 bisco, Jun 8, 2017
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Determining your battery's health isn't a black art. Either get yourself something like Solar BA5 tester, or have a battery retailer (or the dealership) test it, with a pro-level tester. For starters, test (at the jump start point is fine) with a multimeter with the car off, report what voltage it's reading.
     
    #6 Mendel Leisk, Jun 8, 2017
  7. bisco

    bisco cookie crumbler

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    my riding mower was making a machine gun sound when i tried to start it, so i called the local garden center guy, and he says it's the battery.
    he stops by with a new battery on the way home from work and installs it. while waiting, i had released the traction control levers and pushed it inside the barn.
    now it only clicks. he says, i thought it was machine gun, i said it was. well now it's the solenoid he says.
    so he takes a jumper cable and jumps the positive terminal to the starter motor. a huge flash, and lucky he wasn't hurt, i think he grounded it by mistake.
    this guy is the owner, not a mechanic. now i'm reading online that the engine won't start if the traction levers are released.
    he came to pick it up today, i'm just hoping he didn't burn my starter motor out.
     
    #7 bisco, Jun 8, 2017
  8. Maarten28

    Maarten28 Active Member

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    The relevance to this topic is...?

    But I think your battery has just gone flat. First it was just good enough to engage the starter motor a bit so the bendix comes out but after that the starting current makes the voltage drop which makes the starter stop, and then it all starts again, later the voltage is so low that only the solenoid clicks.
    Depending on the age of the battery you could be ok with charging it but you might have to replace the battery.
     
    #8 Maarten28, Jun 9, 2017
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  9. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    There is no 12 volt starter motor, no bendix spring, no solenoid in a Prius. The high voltage Motor/Generator 1 starts the engine and it is always engaged. The 12 volt battery powers the computers and the high voltage relays.
     
    #9 JimboPalmer, Jun 9, 2017
  10. fuzzy1

    fuzzy1 Senior Member

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    I believe he was referring to Bisco's riding mower, not OP's Prius.
     
    #10 fuzzy1, Jun 9, 2017
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  11. bisco

    bisco cookie crumbler

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    apologies, i had lawn chat and prius chat up at the same time, and typed into the wrong one.:oops:
     
    #11 bisco, Jun 9, 2017
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  12. NavyLCDR

    NavyLCDR Active Member

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    That's OK. I've gotten my lawn mower and my Prius mixed up before.....
     
    #12 NavyLCDR, Jun 10, 2017
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    #13 Mendel Leisk, Jun 10, 2017
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  14. bisco

    bisco cookie crumbler

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    they got the old man part right.:p
     
    #14 bisco, Jun 10, 2017
  15. NavyLCDR

    NavyLCDR Active Member

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    I heard that was a pretty slow movie.... :ROFLMAO:
     
    #15 NavyLCDR, Jun 12, 2017
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