12V Battery Question

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Chodronish, Jan 3, 2018.

  1. Chodronish

    Chodronish Member

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    I think my 12V battery is nearly dead. I know it is generally not good to jump another car with a Prius, but I am wondering if it is okay to jump a Prius with another Prius to drive to replace the battery? Or do I need to try to figure out how to replace the battery myself, which is not super appealing unless it is super easy - I am not very handy. It is parked head first in my garage, btw. :(
     
  2. bisco

    bisco cookie crumbler

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    no problem jumping one prius to another. the donor car should be off. don't mess up the positive and negative.:)
    if you don't care to install a new battery yourself, call around for the best price. or have a local mech put one in.
    my guy just put one in my daughters car for $320. in an emergency. if i had more time, i would have shopped around.
     
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  3. Chodronish

    Chodronish Member

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    Thanks! So don't turn the donor car on, just connect the battery terminals under the hoods? How long should I leave them connected?
     
  4. bisco

    bisco cookie crumbler

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    just connect them and fire away, it's the same as putting the battery in the car. unless there is an internal short in the bad battery, then you would have to remove it from the connections.
     
  5. Chodronish

    Chodronish Member

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    By fire away, do you mean start the second car? Sorry to be so high maintenance. And for how long?
     
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  6. bisco

    bisco cookie crumbler

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    just push the start button like you would normally. after you have connected the jumper cables. no worries, i have two high maintenance children.:p
     
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  7. LEVE

    LEVE Member

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    Have you tried this

    :


    Replace the Aux Battery:

     
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  8. Chodronish

    Chodronish Member

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    I did not try that but wish I had when I had some power at least. I can't do it now, because I don't have enough juice. The car is dead. The map light will come on very dimly, but that's it. Good to know for future use though! Can a 12V get too dead to jump? I was planning to jump it in the morning as described above (when I have more light to see to jump it) and drive it straight to Toyota service dept. in Naperville, IL.
     
  9. bisco

    bisco cookie crumbler

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    it's possible. if it won't jump, you have to remove it from the circuit by disconnecting the negative.
     
  10. Chodronish

    Chodronish Member

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    Going to try jumping it now actually, if I can get the fuse box cover off! Could be a little more specific? @bisco, any advice on getting the fuse box covers off? I had no problem in past Prius, but I am having a hard time with these. Never mind, found a video where a guy showed exactly where to press and no problem.
     
    #10 Chodronish, Jan 3, 2018
    Last edited: Jan 3, 2018
  11. LEVE

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    I'm not of fan of jumping a Prius using the connectors up under the hood. I guess I'm more of a purist. Also, I want to protect the car from my possible mistakes. So, how to do that?

    You can protect the car by isolating the aux battery and charge the battery.

    It's quite easy. All you have to do is to gain access to it and then remove the negative cable. On a Prius Gen 2 (2004 - 2009) it's often easier to remove the negative battery cable where the cable bolts to the body of the car. IIRC, it's a 10mm bolt that is easily removed (at least it is on my Gen1's and Gen 2 , 2005).

    Now your battery is isolated from the car. You can put a charger on the battery knowing that your car is safe. Even if you'd make a mistake and reverse the charger polarity (swap positive for negative and negative for positive... hook it up backward) the problem won't destroy the car's electrics.

    I'd also advise buying a charger, the one I use was $25 at Harbor Freight Tools. But it's an easy way to keep the battery charged if it's left for a while.

    If my car will sit for over a week without starting, I'll pull the negative cable. It's quick and easily restored when I want to use the car. I've had the car sit over a month this way and it starts right up when I reconnect the aux battery.
     
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  12. padroo

    padroo Senior Member

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    Do you have an owners manual, the directions are there to tell you how Toyota recommends jump starting a Prius.

    You might search online and download the owners manual and put it on your computer.
     
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  13. Mendel Leisk

    Mendel Leisk Sand Pounder

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    The order of connection is:

    1. Connect red jumper cable to donor car positive post.
    2. Connect other end of red jumper cable to Prius jump start point (also positive).
    3. Connect black jumper cable to donor car negative post.
    4. Connect other end of black jumper cable to substantial bare metal on Prius body or engine.

    Start Prius.

    Disconnect in opposite order.

    There's a very simple reason for the order the cable connections: what you DON'T want to do, is initially connect red and black cables at either end, and then be wandering around with the two cables at the other end. Touch those together, or touch them both to a single piece of metal, and you've just completed a very short, low-resistance circuit.
     
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  14. Chodronish

    Chodronish Member

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    Yes, batteries are scary business! I am relieved to report that I have successfully jump started the 2007 Prius with the 2008 - in our lovely 4 degree weather (-9 wind chill). I utilized the advice here, the manual, and online videos. I thought I was not supposed to turn the donor car on, but it turned out I had to turn it on for around 5 minutes and depress the gas pedal slightly as suggested in the manual and videos and in regular battery jumping. The 2007 started up fine. I even was able to check the diagnostic screen as described and it showed normal. Hopefully it will start up okay in the morning now. Do you all think it's a given that I need to replace the 12V now? My step-son drove it last, so I am not aware of anything that should have drained the battery. It was fine a few hours before I went to start it (he drove it). Perhaps it's just old and should be replaced? Great learning experience, if not entirely pleasant or cursing free. Okay, an addition here is that I checked it again because I rewatched the diagnostic screen video and saw that I had failed to check the battery in auxiliary mode, so I went back out to do so and it isn't starting. The dash lights do come on, but the car doesn't start, so I am anticipating jumping it again in the morning and driving to Toyota for a new battery.
     
    #14 Chodronish, Jan 3, 2018
    Last edited: Jan 3, 2018
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  15. bisco

    bisco cookie crumbler

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    sounds like the right decision, all the best.(y)
     
  16. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Jumper cables invariably come with the positive and negative cables bonded together for most of the run, just splitting apart for the last foot or two at either end. I'm not sure this is a good practice, can in fact increase the chance of short circuits.

    If you pull them completely apart, and then when hooking up handle ONE cable at a time, while leaving the other cable well out of reach, you're more likely to stay out of trouble.

    Start with with positive (red) cable: connect one end to donor car, other end to dead car. Then get the negative (black) cable, connect one end to donor cable, other end to dead car.
     
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  17. fotomoto

    fotomoto Senior Member

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    Great example for keeping a battery booster/jump pack on hand.

    A hybrid doesn't need to be jumped to "crank start" the ICE, it only needs to supply 12 volts @ low amps to bring the computers online. The large and very capable HV battery cranks the engine after the computers are on-line. Thus, a battery booster/jump pack device has no problem delivering enough power to start a hybrid because of the low amps requirement.

    In addition to the typical jumper cable connecters, some packs also have a power plug port for the convenience of jump starting through an interior "cigarette lighter" plug. No way I'd use that to try and crank start an ICE vehicle but it should be able to bring a hybrid online. Anyone try this?

    There are numerous versions for sale and this unit is just provided as an example of what I'm referring to. I have no experience with it and is not intended as a recommendation:

    STANLEY FATMAX BC8S 8 Amp Battery Charger with 2 Amp Maintainer

    On the flip side the best advice is to never use the Prius to jumpstart a dead conventional ICE vehicle that needs to crank start the large gasoline engine by battery power alone. Sure it can be done but the results are often VERY costly if done wrong. I personally have turned down requests in parking lots but would help in true emergency situations (I'd try my tiny jump pack first before breaking out their jumper cables).
     
    #17 fotomoto, Jan 4, 2018
    Last edited: Jan 4, 2018
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  18. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Yeah jump pack is always preferable. I always carry one, in the hatch tray. The only time I've needed to use it on our car is as a memory saver, lol.
     
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  19. fotomoto

    fotomoto Senior Member

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    BTDT. (y)
     
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  20. bisco

    bisco cookie crumbler

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    hence the term 'insurance'.
     
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