12V battery isolator/switch

Discussion in 'Gen 2 Prius Main Forum' started by priumium, Dec 4, 2025 at 12:06 PM.

  1. priumium

    priumium Member

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    I finally tested to install a battery switch for the negative/ground terminal on the annoying trunk battery placement in my gen 2s.

    I wish to recommend this to everyone DIY since it makes me able to cut power over winter or when doing maintenance work without even removing one piece of the trunk pieces.

    Just by opening the right backlight cover I am now able to reach this switch and cut 12V. This might have been posted before, but I failed to find anything like this.

    I bought one version from temu first, this had the best design in my mind. I had to grind the pole down a bit, but this version has adaptable screws that easily fits the small sized poles that the Prius uses and locks them into place real good.

     
    #1 priumium, Dec 4, 2025 at 12:06 PM
    Last edited: Dec 4, 2025 at 12:25 PM
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  2. PriusCamper

    PriusCamper Senior Member

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    That's a great looking design but there's no way I'll buy it from Temu. I wonder who else sells them?
     
  3. priumium

    priumium Member

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    (Why not temu? Tariffs? Sex dolls..?)

    For your information I have failed to find this much smarter design anywhere else. Contact the seller directly and ask, it seems like a very much smarter version with the screws.

    I bought four different designs from AliX and the other ones are all to big for the poles and are also hollow (bad for grinding) and without screws! Easily fixed with a drill, but I have now bought three of these instead.
     
  4. priumium

    priumium Member

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  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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    There are also switches that don't directly connect to the battery posts. Depends on the application, ease of access.
     
  6. pasadena_commut

    pasadena_commut Senior Member

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    Yeah. If I was going to do this I would pick up a battery to ground cable at the junk yard and splice a switch into it.
     
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  7. priumium

    priumium Member

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    Those are marine versions and are good, but the switch is then loose unless you fasten it to something sturdy. That’s a big plus of this design (pun).

    This was flawless in my mind. Reachable from the lower cover.
     
  8. VelvetFoot

    VelvetFoot Active Member

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    Even on an older Prius, don’t you lose some settings when you disconnect the battery?

    also, do you have a link for the posted picture?
     
  9. priumium

    priumium Member

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    Indeed, radio channels, clock and so called learned values are reset. That might be befinitial in some scenarios.

    I am not sure how fast this happens, Toyota states 90 seconds to empty all current.
     
  10. ChapmanF

    ChapmanF Senior Member

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    Hold on a sec. Are you thinking this happens while the car is off?
     
  11. priumium

    priumium Member

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    No, I do not, but running short trips when the battery is in bad shape or has been emptied previously and lost 80 percent capacity to store the charge, the hybrid battery will waste many A on it, especially when below zero.

    When stored the 12V gets destroyed due to many many factors. It’s even in the manual to disconnect it when storing for more than a couple of weeks, as you know. When big subzero, this value can be a few hours..
     
    #11 priumium, Dec 7, 2025 at 5:51 AM
    Last edited: Dec 7, 2025 at 5:58 AM
  12. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Maybe in your translation? Just curious, I don’t recall seeing that in the North American owners manual.
     
  13. VelvetFoot

    VelvetFoot Active Member

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    This dude is in Sweden. It gets cold in Sweden. :)

    edit: Then again, it gets cold in Canada....
     
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