Emergency backup battery to start Prius

Discussion in 'Gen 3 Prius Accessories and Modifications' started by bobzchemist, May 10, 2017.

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  1. bobzchemist

    bobzchemist Active Member

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    Currently, I'm using the Antigravity Batteries AG-XP-10 plugged into the cigarette outlet as my emergency backup battery. My assumption was that if I did something stupid (an all-too-common occurrence) like leave a door open overnight, I'd be able to attach the XP-10 to the jumper terminals and have enough juice to start the car even though the 12v was dead. I know the cigarette outlet goes dead when the car is off, so if the 12v battery runs down, it can't pull the charge away from the XP-10. (Using the XP-10 has the added benefit of being able to jumpstart someone else's car, which you can't really do with a Prius)

    Having just done some research on batteries, isolators and chargers, I'm now a little curious.

    Would there be a way to use something like the Cooper Bussman battery separator (or some other device) to either switch to a smaller, emergency battery or just shut off power completely once the main 12v battery was depleted too much? I know I can set this option on my laptop, so that it will auto-shutdown when the charge hits 10% - does anyone know if it's possible to implement this on a larger scale?

    Battery Separators

    Alternatively, would it be possible to use a separator or isolator to keep a second, smaller, emergency battery always charged, but isolated/separated from the main 12v battery so that it wouldn't discharge if the main battery ran down? More importantly, is it possible to hook that emergency backup battery up so that I wouldn't have to open the hood and manually attach cables to the jumper points to start the car?
     
    #1 bobzchemist, May 10, 2017
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    There's a bolted positive 12 volt cable running into the under-hood fuse box that you can add a pigtail connectored wire, and with another one attached to a grounded bolt, you can cobble a connector. I've done that for my CTEK charger, they come with a capped connector and pigtail ended wires.

    I've left that just dangling, adjacent to the fuse box. I still have to pop the hood, but it saves having to pull off the fuse box lid, employ the somewhat insecure alligator clips. I though of extending the connector, splicing in some wire, enough to run it out through the front grill. But I'm a little leery, about having readily accessible 12 volt plug out in the open, just in case some joker decides to short it out or whatever.

    There's pics of the fuse box 12 volt positive bolted cable location in fuse box near the beginning of this posting. One with and one without the cover. The cover has tabs down the side the sides that need to be depressed to pull it up, and then rotate it. There's also tabs on the top, that apparently do nothing, lol.

    The RetrofitSource Xenon Installation Guide on 2015 Prius | PriusChat

    @NutzAboutBolts has a short video on getting this cap off, in the maintenance sub-forum, video number 22:

    Nutz About Bolts Prius Maintenance Videos | PriusChat
     
    #2 Mendel Leisk, May 10, 2017
  3. NavyLCDR

    NavyLCDR Active Member

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    #3 NavyLCDR, May 10, 2017
  4. Sam Spade

    Sam Spade Senior Member

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    Your present plan is elegant in it's functional simplicity.
    Why mess with it ???
     
    #4 Sam Spade, May 10, 2017
  5. bobzchemist

    bobzchemist Active Member

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    That's an interesting solution. Using that, I could keep the charger under the hood and just have to press a button to jump-start the Prius.

    It looks like it connects directly to the battery, though - I'd have to come up with a way to connect it under the hood at the fuse box, and then find a way to keep the XP-10 charged from a fuse that's only on when the car is in the Ready state. Plugging it into always-on power takes me back to the problem of keeping it isolated from a steadily discharging 12v battery.
     
    #5 bobzchemist, May 10, 2017
  6. ChapmanF

    ChapmanF Senior Member

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    I have one of those little Antigravity packs myself, and for a time I half-seriously considered sticking it permanently in the back of the car with the battery, charging it from my switched power distribution thingy, with a fat relay isolating the jump output ... and controlling the relay from the dash if I could get one of these pushbuttons but engraved "JUST START ANYWAY".

    [​IMG]

    But as it turns out, (1) that outfit doesn't do custom engraving on their switches, and (2) it's more convenient to have the jump pack in the glove box. After all, I haven't yet needed to use it to start the Prius, but I did take it out and start some stranger's van with it recently, which would have been a lot harder if it had been buried in back and wired in.

    -Chap
     
    #6 ChapmanF, May 10, 2017
  7. NavyLCDR

    NavyLCDR Active Member

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    The permanent connections available in/near the fusebox were shown in the links given in Mendel Leisk's post #2.
     
    #7 NavyLCDR, May 11, 2017
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