2007 Prius: Dead 12v battery, back door catch-22

Discussion in 'Gen 2 Prius Main Forum' started by RichPasco, Sep 9, 2012.

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  1. RichPasco

    RichPasco Richard C. Pasco, Ph.D.

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    Help! I have a 2007 Prius which today, for the first time ever, refused to start. I pressed the Start button and all that happened is the "check engine" and "airbag" lights came on (dimly), and the green LED on the "P" (park) button began blinking. I pressed the "Start" button again but nothing I can do will change this. The car is sitting in my garage now, in this condition. I turned the dome light on briefly and it was very dim, so I suspect the 12v battery is dead. Only problem is, to access it requires opening the back hatchback door, which won't open without 12v power. Meanwhile the tiny bit of power that's left is being drained by the system in it's half-on condition (above). If I could get to the battery I could connect an external charger to charge it up enough to start it but I can't. What should do?

    Update: I got in a side door and removed enough panels from the floor of the trunk to release the latch manually and open the door. With a 1.5 amp float charger connected to the battery, it shows 5 volts (out of 12). I'm now wondering whether charging it will suffice or I'll need to buy a new one.
     
    #1 RichPasco, Sep 9, 2012
  2. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    I have a G3, but there is a charge/jump terminal in the engine compartment for my subtype.
    If you look in the owner's manual under "what do I do if I have a battery that's TANGO-UNIFORM..." there will be detailed instructions...or somebody with a G2 will probably confirm my suspicions that you're able to boost/boot the car from under the hood.
    I'm sure that the folks in Aichi anticipated this.
    Be careful when you do it, but you should be able to use another battery or a battery tender to boot your car. Then? go get yourself another one.

    Good Luck!
     
    #2 ETC(SS), Sep 9, 2012
  3. bubbatech

    bubbatech Member

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    The rear door latch is accessible via a door from the inside. Once you open it from there, you will be able to open the hatch. You can then disconnect the 12 volt battery and charge it. You may get some errors when you reconnect, but they should clear after two or three starts. If this is the original 12V battery, it would be 4-5 years old by now and therefore likely requires replacement.
     
    #3 bubbatech, Sep 9, 2012
  4. bubbatech

    bubbatech Member

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    Also...There are jump terminals under the hood.
     
    #4 bubbatech, Sep 9, 2012
  5. RichPasco

    RichPasco Richard C. Pasco, Ph.D.

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    Thanks to all who responded so quickly. I was able to start the car by jumping the 12v battery. When the car was running I measured 13.7 volts across the battery terminals. Now, having turned it off again, I connected a 1.5 A float charger and a digital multimeter, and am watching the voltage on the battery terminals drift slowly downward: 12.15v, 12.10v, 12.05v etc. I think it's clear that the 12v battery will need to be replaced.
     
    #5 RichPasco, Sep 9, 2012
  6. PriusCamper

    PriusCamper Senior Member

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    Well... Actually, you have to fully charge the battery before you decide if it's bad... the 13.7volt measurement is just the battery being charged, not how charged the battery is... Try charging the battery longer, maybe a long drive?
     
    #6 PriusCamper, Sep 9, 2012
  7. RichPasco

    RichPasco Richard C. Pasco, Ph.D.

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    PriusCamper, I know that the 13.7 volt reading is "being charged." That reassures me that the car's built-in charging system is delivering a voltage which should charge the battery.

    What gives me concern is that even when the 12v battery is hooked to the 1.5 amp charger, its voltage drifts downward below 12.1 volts. At that charging current, the voltage should drift upward slightly (toward 12.6 volts).

    We did go for a "long drive" just yesterday (about 25 miles at 50 MPH), only to find the car wouldn't start today, and was at 5 volts. That's why I think it needs to be replaced.
     
    #7 RichPasco, Sep 9, 2012
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    That 1.5A charger will literally take days to charge your battery - if it could be charged. The battery is probably dead anyway. If you want to try charging it, leave the Prius READY overnight (assuming you have sufficient fuel in the tank so the engine can run as needed.)

    The OP would have to drive for hours & hours, and that is not really needed - he just needs the Prius to be READY. There is no difference in charging time whether vehicle speed is 0 mph or 100 mph.
     
    #8 Patrick Wong, Sep 9, 2012
  9. RichPasco

    RichPasco Richard C. Pasco, Ph.D.

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    We're leaving on a trip and are certainly willing to take days to charge the battery while we're gone. But the fact that its voltage goes down rather than up while on the charger suggests that no number of days will charge it.

    OK, so just yesterday the Prius was READY for about an hour, during which time the car apparently worked normally. So why won't it start today? Seems to me the "12v" battery which weighed in at just 5v is the culprit, especially since its charging circuit delivers 13.7 volts (see above).
     
    #9 RichPasco, Sep 9, 2012
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, I personally would replace the 12V battery now, rather than waste more time on it.
     
    #10 Patrick Wong, Sep 9, 2012
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  11. John H

    John H Senior Member

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    I would recommend the Optima Yellow Top model built for the Prius with the T1 posts.
     
    #11 John H, Sep 9, 2012
  12. RichPasco

    RichPasco Richard C. Pasco, Ph.D.

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    Hey John, why is the Optima Yellow Top better than any others? Do they pay you for recommending it? :)

    By the way there is no listing for the 2007 Toyota Prius on the Optima web site
     
    #12 RichPasco, Sep 9, 2012
  13. fuzzy1

    fuzzy1 Senior Member

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    Based on my work with other kinds of batteries, I wouldn't take that as an indication if it had been on 'Ready' or on a charger only a few minutes. After several hours, then would I take that as a definitive answer.
     
    #13 fuzzy1, Sep 9, 2012
  14. MJFrog

    MJFrog Active Member

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    The Optima Yellow Top is a deep cycle battery. This means that it tolerates being fully (deeply) drained much better than other batteries.

    Here's the link you want:
    OPTIMA® Batteries 8171-767 DS46B24R YELLOWTOP® Prius® Auxiliary Battery :: OPTIMA® Batteries

    BTW, in addition to John, there are MANY owners on this site (myself included) that own and are extremely pleased with the Optima Yellow Top. Then there are others who think the whole things just a gimmick to sell expensive batteries.
     
    #14 MJFrog, Sep 9, 2012
  15. John H

    John H Senior Member

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    #15 John H, Sep 9, 2012
  16. RichPasco

    RichPasco Richard C. Pasco, Ph.D.

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    #16 RichPasco, Sep 9, 2012
  17. fuzzy1

    fuzzy1 Senior Member

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    Who else had it, Autozone?
     
    #17 fuzzy1, Sep 9, 2012
  18. edthefox5

    edthefox5 Senior Member

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    Got my Yellowtop at Advance Auto parts online 15% 199.99 plus $50 instore coupon against $100 purchase.
    Pick it up at the store.

    And like most people it was discharged a bit. Put it on the charger till it hits 0 draw before install.
     
    #18 edthefox5, Sep 9, 2012
  19. gone2green

    gone2green grumpier than the grumpiest old man you know ;)

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    I got mine from the elearnaid.com site got in 2 days
     
    #19 gone2green, Sep 10, 2012
  20. R-P

    R-P Active Member

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    Not to discourage anyone, but the yellowtop has been used in the car-audio scene a lot. There is talk of a sharp drop in quality several years ago: the used materials seems to be of lesser quality then, say 10 years ago, yet the sales price stays the same.
    I cannot substantiate this claim, I am only repeating what I have heard and it was not a single claim and it was not a claim without evidence.

    If even remotely true, they are staying afloat on the reputation they build over a decade ago and are throwing it away now...
     
    #20 R-P, Sep 10, 2012
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