Adding second 12v battery

Discussion in 'Gen 3 Prius Accessories and Modifications' started by Terrell, May 2, 2019.

  1. Terrell

    Terrell Member

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    I'm working on adding a second 12v battery. The corner in the rear on the driver's side looks like a good place for the second battery. What is the purpose of the screw which comes up there? Is that for a second battery tray? Or what? (Currently, it holds the plastic tray. But that can't be it's original purpose.)

    I was able to get OEM parts at a junkyard for the battery cables, including a vent tube. Nice thing about the OEM positive terminal is it comes with a 140A fuse built in. $20 total for both cables and vent tube.

    I plan to add a Blue Sea Systems SI-ACR Automatic Charging Relay, so the two batteries are in parallel while charging, and while discharging they are disconnected from each other. That way my refrigerator won't run down the Prius 12v battery. Plus I can charge both batteries with a portable solar array in addition to the car's inverter.
     
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  2. Montgomery

    Montgomery Senior Member

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    If you get this done, I would love to see photos of how you did it. Anything to let me run my radio without the car on more than 20 minutes sounds intriguing.
     
  3. Greenteapri

    Greenteapri Active Member

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    Sounds like a fancy refrigerator. I didn't know they made one efficient enough to run off a 12v source.
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    The threaded stud is for clamping a black plastic bucket that is supposed to be there. Its just a semi-triangular cubby hole storage container that is shaped to fit that area. It has a hole in the bottom which fits over that stud. Then a plastic nut is threaded on to retain it. The edge of this bucket has a lip that supports the large plastic storage area under the trunk floor.

    Looks like this photo from ebay.....

    cubby.jpg
     
  5. Terrell

    Terrell Member

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    I'm taking photos. :) I found the local junk yard to be a treasure source for some parts, but am waiting for some more new parts.
     
  6. Terrell

    Terrell Member

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    There are several which run off 12v. The one I have is expensive, but it is a real refrigerator made for the bumps of travel, and is able to freeze as well. It's a Dometic CFX 28. It will fit behind the front passenger seat (if the seat is shoved forward a bit), as well as in the back of my Prius.
     
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  7. Terrell

    Terrell Member

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    I know about the plastic bucket/tray that's there. It's held down by that push-on plastic nut. But I doubt that was the original purpose. The stud/screw that's there is solidly anchored, way more anchor than a plastic bucket needs. Plus it's recessed. The plastic tray doesn't need that either. My guess is that the original Prius design had something else in that corner spot. The Japanese inverter? An extra small battery? Does anyone know?

    Tomorrow I plan to go to the junk yard again to see if I might find a battery holder that fits that stud and the recess.
     
    #7 Terrell, May 2, 2019
    Last edited: May 2, 2019
  8. ASRDogman

    ASRDogman Senior Member

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    I believe the owners manual says the drivers side rear area is a storage space.
    Maybe where the are right hand side drivers steering the put the battery on the left? :)
     
  9. Greenteapri

    Greenteapri Active Member

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    Thanks for the info. How long can you go without needing a charge?
     
  10. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    If you were to pull out the current 12 volt battery, and find a matching threaded stud to the driver's side, that would strengthen your argument. Or maybe..., the right side drive vehicles have the 12 volt battery on the left side??
     
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  11. ChapmanF

    ChapmanF Senior Member

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    I'm pretty sure the body well on the battery side is a lot deeper than on the stud/plastic-bucket side. If there was ever a different official thing that went there, I'd guess it was not as tall as the battery.
     
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  12. Terrell

    Terrell Member

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    Depends on what I set the temperature of the refrigerator/freezer to, and how hot it is outside (inside the car). It holds the set temperature pretty well (within around three degrees F). When driving, I plug it into the car's 12v battery by way of an extra 12v power outlet I wired to the battery (with a 10A fuse on the positive side). When not driving, I run it off my second battery, which is being charged by a 120W portable/foldable solar panel. The second battery went out on me after three days of overcast skies (it's also an old battery with maybe half it's life left). This is a reason I'm installing the second battery in the car, so it can be charged by the car as well as the solar panel.
     
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  13. Terrell

    Terrell Member

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    The battery compartment on the right side has holes for the battery tray (and even holes for a larger battery tray and larger battery), and is lower than the compartment on the left side. The compartment on the left side has no holes to anchor the battery tray. Instead, it has a screw which sticks up, and it seems well anchored for just holding a plastic tray. Plus there is a large hole in the sheet metal with a rubber plug in it. What's that for?

    The USA version of the Prius uses that left side for a small storage tray. But with that screw sticking up, and the hole with the rubber plug (actually, there are two holes with rubber plugs, but not in a position to anchor the regular battery tray), I imagine there's a version of Prius somewhere that utilizes that space for something other than a tray.
     
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  14. Terrell

    Terrell Member

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    You are correct about the deeper battery side. I've heard that the Japanese version could have an inverter. Could it have gone in this space?
     
  15. Terrell

    Terrell Member

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    And... here's what I did:
     
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  16. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    It's not playing. :(
     
  17. Grit

    Grit Senior Member

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    Playback on websites have been disabled by owner. Oh well back to square one.
     
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  18. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Click on this, takes you directly to YouTube, and then it works:

    upload_2019-5-19_7-15-24.png
     
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  19. qettyz

    qettyz Active Member

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    Video should be playable from YouTube, uploader has disabled feature that video can be embedded to another website.
    @Mendel Leisk post a direct link to the video.


    Edit: that works also
     
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  20. CR94

    CR94 Senior Member

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    How much current does that refrigerator demand?

    Incidentally, we might be better off without that tray and its comically overdesigned hold-down stud. They waste much of the space otherwise available.
     
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