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9V Module in 12V Outlet to Save Presets?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by jdcollins5, Oct 28, 2009.

  1. jdcollins5

    jdcollins5 Senior Member

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    A co-worker was telling me this morning about going to AutoZone to replace a battery. He said first the technician inserted a 9V battery module in his 12V outlet to save his presets. He removed the battery and replaced with a new one. All radio presets were saved.

    Has anyone else heard of this and specifically has anyone done this on their Prius? Sounds like a great idea, especially with all of the presets on the Nav units.
     
    #1 jdcollins5, Oct 28, 2009
  2. jdcollins5

    jdcollins5 Senior Member

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    After creating this post I thought about reading other posts that stated that the 12V outlet is not connected to the 12V battery when the system is off. Others had discussed using this as a way to charge the battery when leaving it for extended periods of time.
    Is this correct?

    Sorry. Has anyone heard of using the 9V module on non-Prius vehicles?
     
    #2 jdcollins5, Oct 28, 2009
  3. rrolff

    rrolff Prius Surgeon

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    Both 12V outlets are switched - and off when the car is off. Plugging anything into them when the car is off does nothing. That said, most of today's radios keep the data in FLASH, so the settings are saved.

    If you want to do something out of the ordinary, you could sire one of the outlets directly to the battery...
     
    #3 rrolff, Oct 28, 2009
  4. qbee42

    qbee42 My other car is a boat

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    If you want to save presets during a battery swap, connect another 12V source to the jump points under the hood. This will float the bus during the swap.

    Alternately, you can switch the Prius on and swap the battery while the car is powered up. The DC to DC converter will keep the 12V bus powered during the replacement. This method makes me a bit more nervous because of the risk to powered up components. Either way, be vary careful to avoid shorts and polarity reversals.

    Tom
     
    #4 qbee42, Oct 28, 2009
  5. jdcollins5

    jdcollins5 Senior Member

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    rrolff

    Thanks,

    Dwight
     
    #5 jdcollins5, Oct 28, 2009
  6. hobbit

    hobbit Senior Member

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    I have explored this somewhat, using a direct keepalive on the 12V
    ... but I did use 12 volts. I suspect that most of the memory
    keepalives internally use 5V, and if you feed enough voltage to get
    above the minimum running threshold of the little regulators inside
    the ECUs then 9V might be enough to keep the memory alive.
    .
    But not through the power outlets, for the reasons stated.
    .
    _H*
     
    #6 hobbit, Oct 29, 2009
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    What about using the vehicle jumper plug in the front. Of course there is the potential for a little fight:
    12 VDC, 600 A. auxillary battery vs. 9 VDC 450 mAH
    ​
    [​IMG]

    I'd probably want to use a pair of 6 V lantern batteries and possibly a diode to prevent reverse current flow.

    Bob Wilson
     
    #7 bwilson4web, Oct 29, 2009
  8. jdcollins5

    jdcollins5 Senior Member

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    If you used the 9V battery, I think you definitely want to use the diode when you first plug it in with the 12V battery still in service to block the higher voltage. Once the battery is removed then the 9V current could flow to the ECU to keep the presets. Connecting it to the front jumper bar seems like the best idea since the 12V outlets are not connected when off.

    My co-worker was going to go by AutoZone and get some info on this 9V module that they used. Evidently this module must contain the blocking diode if he plugged it in to the 12V outlet prior to removing the battery. Of course you could easily make your own like the one you show in your picture. I need to look in to this.
     
    #8 jdcollins5, Oct 29, 2009
  9. F8L

    F8L Protecting Habitat & AG Lands

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    This idea worked well on most conventional cars but for the above reasons it does not work on the Prius unless you have the 12v outlet mod that Coastal Electronics sell swhich allows the use of the 12v outlet even when the car is off.
     
    #9 F8L, Oct 29, 2009
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