12v issues 2010 and mpg fail

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by MikeV, Nov 22, 2020.

  1. MikeV

    MikeV New Member

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    I have a 2010 Prius with 160K miles. Since August I noticed a dramatic drop in MPG from Avg 44-46 down to 39-40. In Aug I had oil change and set of new tires. I waited a couple fills to see if it corrected. I reset psi on tires to 35 from 32 and checked oil although I used two Auto chains and never trust what they did or did not do. Example when I had the 4 new tires my hood was up and I questioned the manager why my hood is up when I am getting 4 new tires? In any case after reading several posts from many sources there seems to be a vague consensus that a failing 12v battery could be culprit. I used the card auto DX to look at the 12v when car is off it has been 10.9 to 11.8 if I tested after a drive or something so its def low. When the car is on and I am driving it only gets to about 13.6, though it should get over 14 right? I called Toyota since the battery was replaced in 2016 before I purchased it and its still under 84month prorated warranty but was told they need to DX first and of battery tests ok then I will get charged for the DX and no battery warranty would apply. I drive the car almost every day for at least a 20 or so mile round trip. Sometimes it will sit for about 2 days but never more than that. I would really like to get a little more educated on the 12v battery issue before taking it into Toyota. The Hybrid battery will usually stay just shy of 1 or 2 bars except in August – present it does run down faster if I am using the AC and in a lot of stop-go traffic but on Highway it recovers quickly. Any tips advice?
     
  2. barnabas

    barnabas Junior Member

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    My home watch people ruined my 12V battery by forgetting to reconnect the trickle charger after driving the car. The battery was just short of 5 years old so maybe it was getting weak. This is the third battery in 11 years and 87000 miles. The mileage on my 2010 Prius 3 had been declining for a year. When my 12V battery was replaced the mileage when from about 44MPG back to 57MPG.

    Barnabas
     
  3. Ed Beaty

    Ed Beaty Active Member

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    "My home watch people ruined my 12V battery by forgetting to reconnect the trickle charger after driving the car."

    Maybe, maybe not: Again, there is an important difference between a 'trickle' charger and a battery maintainer. The former does NOT stop charging your battery, and can ruin it. The latter has circuitry in it which will stop the charge when it is full, and just hold the charge at that point, causing no harm to the battery. By using that trickle charger, you may have already compromised your battery before your home watch people even came into the picture.

    Ergo, barnabas: do not call a battery maintainer a trickle charger......
     
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  4. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Just editorial, what is "DX"?

    If you measured voltage with the car off, could be a battery going out, but again: what the heck is "card auto DX"?

    What are your new tires?

    160K is getting into danger territory for clogged EGR and it's consequences. Have you ever cleaned the EGR system and intake manifold? Should clean the throttle body while you're at it.
     
    #4 Mendel Leisk, Nov 30, 2020
    Last edited: Nov 30, 2020
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  5. barnabas

    barnabas Junior Member

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    I hope my terminology does not rattle too many people. I am old school, been retired for 15 years. I use the term trickle charger loosely. I don't claim to be up to date on terminology or theory. I use to specify the chargers and batteries for emergency power systems, large rooms full of batteries, before it was decided it is better not to have too many emergency systems in one place. Many batteries paralleled and in series.
     
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  6. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Avoid acronyms and esoteric terms, speak colloquially, responders will get your drift easier.
     
  7. sam spade 2

    sam spade 2 Senior Member

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    Most auto parts stores, all battery shops and many independent shops will test your battery for FREE.
    Including the time it takes to find the meter and walk it to your car, it should take less than 5 minutes.
    Ask them to repeat the test twice.

    But at the age of your vehicle, there are a lot of factors that could add up to slightly less fuel efficiency.
    Including the new tires......especially since you dropped the pressure.
    As the weather is turning colder is NOT a good time to be doing that.

    I'm kind of surprised that there aren't more replies to this.
    But it HAS been covered before.......MANY TIMES.
     
  8. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    I think he raised pressure, from 32 to 35.
     
  9. Grit

    Grit Senior Member

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    did you mean “homies?” Or did auto correct kicked in?
     
  10. sam spade 2

    sam spade 2 Senior Member

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    Oops. Right.
     
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  11. Grit

    Grit Senior Member

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    someone once replied to me saying a “flush” in their own car terminology is the same as drain and refill when it comes to car fluid servicing. I left the reply alone.
     
  12. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    @NutzAboutBolts uses the term flush, for brake fluid change for instance, and I'm real reluctant to tug on his cape lol.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Pull the mask on the old Lone Ranger, though?
     
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  14. MikeV

    MikeV New Member

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    Sorry, thought everyone was familiar with DX = Diagnose\s. The new tires are Japanese sutimari? and I have been keeping them at 37psi but since the weathers has been bouncing from 70 to 32 in just a week I reset them to 37 as they were down to 32 again
    I will research clogged EGR but is that something a somewhat novice can do on their own. I just spoke to Toyota dealera again today and they have a rigged game. They require testing 12v with their machine and I am at 25% warranty and you need to have them install it as they need the other one on the spot so it will cost around 235. I may just go ahead and do it since most local places are running about 200 for an off brand battery local to me and I dont want one shipped through the mail unless someone convices me otherwise.
    When I check the battery DX from the car the 12v is usually 10.7 to 11.1 volts when car is not started if I drive say 30min or so and stop and check the battery might be about 11.7v but its still low. The big battery is keeping it constant at about 13.6 if I keep DX running while starting the car and driving. Even if turning the head lamps \ radio etc the battery stays at about 13.6 but I notice the big battery indicator starts dropping bars if in stop and go or just idling. If I turn on air\heat the big battery is more impacted. SO I am thinking its spending excess energy keeping the 12v up to speed therefore causing the gas engine to run more to keep the big battery charged which is equating into about a 3-5mpg drop from what I have been accustomed to seeing this time a year
     
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  15. MikeV

    MikeV New Member

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    Yes I agree, I though more replies. The new tires are Japanese I go them from NTB and at a good price. I was using Goodyear, but they are only good for one year no matter the mileage so I have stopped using them. I try to keep the PSI at 37,(do you recommend anything different?? as it has worked well in the past. I temps dropped so they were low for the last 2 weeks and I reset them to 37 2 days ago.
    Toyotal dealer will most likely replace the battery with OEM for 235 ttl since there is still a prorated warranty in play I just am always hesitant with the commercial shops as I have a trust factor of sorts
     
  16. royrose

    royrose Senior Member

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    I have had a replacement battery from O'Reilly for 6 years. AAA tested it for me at an event and said it has plenty of life left. So, non OEM can be good.
     
  17. MikeV

    MikeV New Member

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    I live in central PA. We dont have Oreilleys but i will call the auto zone or auto parts. I checked their site and it didnt appear they carries a 12v. How much was the battery at oreilley? and did they install.
     
  18. royrose

    royrose Senior Member

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    It was about $200. I did the install which was easy. I believe Autozone has a comparable one for the same price but that may have changed.
     
  19. MikeV

    MikeV New Member

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    What is name\part # of battery you got?
     
  20. royrose

    royrose Senior Member

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    I believe it was their house brand Super Start but I just checked their web site and they only list the Optima yellow top t $250.

    Autozone lists this: Screenshot 2020-12-03 182931.png
     
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