12V battery after one month of sitting in the garage

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by AliceLB, Dec 10, 2024.

  1. AliceLB

    AliceLB New Member

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    Hi. I have a 2014 Prius 3. The 12V battery was changed about 4 years ago.

    We'll be out of town for just under 1 month.

    Will the 12V battery likely be fully discharged upon our return? If so, which battery charger do you recommend for jump starting the car?

    We were considering leaving a trickle charger connected while we're away, but I'm concerned about rodents moving in and chewing the wires if the hood is open for an extended period. Though I'd assume the rodents would be just as likely to do so even if the hood is closed.

    Or should we disconnect the 12V battery while we're away?

    Would appreciate your recommendations. Thank you.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Charges don't jump start the car; they charge the battery. We drive around 3000 kms a year (yup), car's garaged, and is pretty much constantly on a charger. I'm using a CTEK 4.3; current iteration of that charger, maybe with some refinements, is CTEK 5. It's been very dependable, but they're getting pricey. Noco's got a good reputation too.

    Yes, makes little difference. I'm using a quick connect harness with our charger (CTEK's come with it), connected at the under-hood fuse box for the positive, and car body for negative. This allows me to connect and then lower the hood gently, closed but not fully latched.

    In lieu of keeping it on a charger this is a good option. Just disconnect and isolate the negative cable from the battery, say stuff the cable end into a heavy glove, out of the way. When you reconnect there will be a few anomolies: radio station presets will be gone, ditto for trip meters. Window auto-up* "may" not work*, the first start-up may be "odd" (I forget how exactly), and that first plus the next few start-ups, the car may do some odd rev-up, think it's reconfiguring something.

    * To reset window auto-up: manually hold the window down button till windows fully down, and continue to press the button a few more seconds. Repeat this for running the window back up. Hopefully it wil relearn with this.
     
    #2 Mendel Leisk, Dec 10, 2024
    Last edited: Dec 10, 2024
  3. bisco

    bisco cookie crumbler

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    my ignorant opinion is that leaving the hood open is more of a deterrent than having it closed because at least it is light in the day, which reduces mouse activity.
    i would put a battery maintainer on it, this is what i have:

    ref=asc_df_B07W46BX31
     
  4. Tombukt2

    Tombukt2 Senior Member

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    The ctek that mendels using It's top notch but reality any of those one to three amp trickle chargers that come with the cord that you connect to your 12 volt in the trunk and then you drill a little hole in the plastic covering panel and stick the cord up through there with its cap on so when you need to leave you can put the SeaTac right in the trunk plug it up to the little silly plug that it came with that's now connected to your battery. Close the hatch with the plug laying on the gasket it will not cause any problems you can even pull cord through the gasket without doing any damage and then plug the ctek into an outlet. And you're good The car can be locked It can be on the trickle charger and everything is good even out in the street kind of if you got a straight shot for your cord although some idiot will come along and unplug it so maybe if people are around they can keep an eye on it and should be stellar when you get back.
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    If you have a multistage battery maintainer (almost any in the last 20 years are ok) I would consider using it for a car sitting for three weeks. If you don't know if your parasitic draw is 30 ma or lower AND you have not done a load test on a greater than 5 year old battery, a charger on a ten day trip might be advisable. Or have a lithium jump starter accessible by the mechanical key that you know works.

    Disconnecting 12v Option:

    It is possible to disconnect the white cable plugged in to the top of the engine fuse box instead of disconnecting the battery negative. No chance of closing the rear hatch with no easy way to open it after creating zero battery power.


    Jump Start Regardless of Precautions:

    To jump start your car (or your friend's in an emergency), you DO NOT want to use jumper cables because of costly damage to your Prius should cables be reversed even for a second at either end.

    A lithium jump box with built in reverse polarity protection can be stored under a seat and will save the day when your 12v battery suddenly and without warning fails. I had one fail after sitting for 10 minutes in a grocery parking lot. No vacation time required when Prius 12v agm batteries get old.

    I keep the Noco GD40 in the car (about $99 on Amazon). Rarely use it other than on other people's cars. It holds a charge for years and can be recharged with an included 12v power plug adapter after use.

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