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Do you think I need a new 12v battery?

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Nanosauromo, May 11, 2020.

  1. Nanosauromo

    Nanosauromo New Member

    Joined:
    May 11, 2020
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    Location:
    California
    Vehicle:
    2016 Prius
    Model:
    Two
    2016 Prius, purchased in August of that year. About 51,000 miles on it now. Before the pandemic hit, the longest it had gone without being driven was 10 days.

    Like many people I started working from home recently, and my Prius sat not being driven for 25 days. Then I tried to start it up to go grocery shopping, the display briefly showed some warning about shifting to park (???) then nothing. The display went dark and the car wouldn't start. There was just a very quiet ticking noise that seemed to be coming from under the hood. I jump-started the car with another vehicle and drove around the block. A couple hours later I did my shopping trip. Everything seemed to be fine...

    Until another week of no driving went by and it wouldn't start again. This time I used one of those portable car battery chargers. Drove around for about half an hour right after, which is what I've read your supposed to do. That was four days ago, and in that time I've been starting it once per day, trying to figure out how long it takes the battery to discharge. So far it's started up perfectly every time.

    Additionally, I took my Prius to the dealership for regular maintenance about two months ago (before the current trouble started) and they didn't mention anything being amiss with the battery.

    So what do you think? Is my 3.5-year-old battery bad and in need of a replacement, or did it just need that recharge, and to not be left sitting for three weeks? If I can avoid spending a bunch of money on a new battery, I'd rather not, but I'm willing to do that if it's necessary.

    Any advice from people who know more about car maintainence than me (an car-illiterate moron) would be greatly appreciated.
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,862
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    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    welcome!

    dealers don't check the 12v as part of normal service. if the car starts, they're good with it.

    the only way to truly know the health of the battery is to swing buy an auto parts store for a free load test.

    if they say it is good, you are going to have to have them charge it up, or buy a charger.

    once you have a fully charged battery (yours or a new one if needed) remove the 12v neg cable when not in use, or buy a battery maintainer.
     
  3. bevhoward

    bevhoward Member

    Joined:
    Oct 25, 2019
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    Location:
    Austin, Texas
    Vehicle:
    2020 Prius Prime
    Model:
    XLE
    fwiw, I just went through the same problem with a 6 month old battery on a 2020 prius prime... there seems to be a design problem impacting the 12v system that was not anticipated by toyota.

    Suggest looking at this thread which has had a lot of input on your subject.

    I second bisco's suggestion that you start using a maintenance charger. When a battery is completely depleted, it is damaged. Hydrometer tests on my 6 month old battery show that it is damaged beyond repair.

    Beverly Howard