dead battery

Discussion in 'Gen 2 Prius Technical Discussion' started by Bob Holliston, Oct 2, 2021.

  1. Bob Holliston

    Bob Holliston Junior Member

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    About once a year my battery goes dead overnight for no reason I can think of. Of course the rear hatch won't open so I have to get to the battery through the back seat which is a pain. Any ideas? Thanks, Bob.
     
  2. sam spade 2

    sam spade 2 Senior Member

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    Do models that old have "Jump points" under the hood ?
    If so, you don't have to "get to the battery".

    And if this has happened enough times that you measure the interval in years, then it is probably time for a new one........and the interval will become less and less.
     
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  3. bisco

    bisco cookie crumbler

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    is it on halloween?
     
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    Open the hood- on the left (driver's) side is the engine compartment fuse block. Inside that (under a red cover) is the (+) jump point. Connect the positive clamp from your booster or charger to that. Connect the negative clamp to something like the attaching stud and nut at the body for the left strut just behind the fuse box. BE VERY SURE YOU HAVE THE CORRECT POLARITY!
    Once you have power supplied to the car, just use the normal (electric) release to open the tailgate as needed. If you do have a charger, just leave it connected underhood for as many hours necessary to fully charge the 12V. Consider having the 12V load tested and replaced if it fails the test.

    Posted via the PriusChat mobile app.
     
  5. Aegean

    Aegean Active Member

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    You can open the trunk from inside when the battery goes dead so I hope you do that and you don’t crawl in the trunk to get to the battery.


    Now I want to share a comment on when to change the 12 battery. There are two options:
    1. You keep the 12v battery until it goes out. The benefit is that you save about $25- $30 for each year you keep it longer. The problem is that you will get stranded. This could be at your house or work but even worse it can be a weekend night in a restaurant or a trip. The second problem is that you will pay almost MSRP price as there is no time to shop around. The third issue is pick up or delivery of the battery which will probably be 2-3 days later especially now with the supply chain issues leaving you without use of the car.
    2. The other option is to change the battery in year 8 or 9 before it fails. Not only you have time to shop around to get a good price but you can also afford shipping times or dealer delays to pick it up. Most importantly you avoid being stranded at the worst time and you keep using your car. Yes if you divide the cost of new 12v battery by 8 years it might cost you an extra $25-$30 dollars for the early decommissioning of a still good battery by a year but you will definitely save at least that off the MSRP of a new battery since you have a few days to shop around and you avoid the risk and inconvenience of being stranded and not using your car for a couple of days.
     
  6. bisco

    bisco cookie crumbler

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    no ideas?
     
  7. rjparker

    rjparker Senior Member

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    #1 Carry a lithium jump box which will also prevent a catastrophic reverse jump. You never know when a light or flakey module will drain a battery, even a new one. Learn how to use it on the front jump point.

    #2 Replace the hatch light with an LED. $1 allows 24 hours of hatch light operation without a dead 12v.

    #3 Replace the 12v battery proactively at 7 years

    #4 Money no object? Buy a lithium 12v battery with Wireless Jump-Starting built-in. You may have to adjust the battery opening slightly.

    #5 Willing to bet $20 on a wifi monitor? Mixed reviews on the Battery Tender Wireless Vehicle Battery Health Monitor. Apparently the setup is cryptic. One might wonder how adding more load to an old battery helps much.
     

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  8. fuzzy1

    fuzzy1 Senior Member

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    Yes, they do. If OP has a used car that came without a hardcopy Owner's Manual, he can find it online here:

    upload_2021-10-8_18-14-26.png

    upload_2021-10-8_18-16-0.png

    upload_2021-10-8_18-16-55.png
     
  9. fuzzy1

    fuzzy1 Senior Member

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    This is also called out in the Owner's Manual:

    upload_2021-10-8_18-25-16.png
     
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