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Added 12V Accessory battery monitor...

Discussion in 'Gen 3 Prius Accessories and Modifications' started by thordehr, Jun 22, 2014.

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  1. GregP507

    GregP507 Senior Member

    Joined:
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    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    Due to the way the Prius is designed, if the user allows the aux battery to go dead, the car becomes "dead in the water," despite having kilowatts of electric power in the hybrid battery. The only solution is to boost the aux battery, which shortens it's life, or ruins it completely.

    I'd like to think I'm thoughtful enough to remember to switch out of acc mode before the battery goes dead, but that's just not the reality. It's bound to happen with me, therefore I'd like an additional reminder for aux battery voltage. I like the idea of a lighter-socket volt-meter, preferably with an alarm which sounds when battery voltage drops too low. I'll be looking for one of those soon.
     
    #21 GregP507, Jul 11, 2014
  2. szgabor

    szgabor Active Member

    Joined:
    Jul 29, 2009
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    Location:
    Oceanside NY
    Vehicle:
    2012 Prius
    Model:
    Two
    Why on earth would be in aux mode in any length of time ??? That is surely not recommended. And make no sense either. Prius is a different car.
     
    #22 szgabor, Jul 11, 2014
  3. GregP507

    GregP507 Senior Member

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    2012 Prius Plug-in
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    Plug-in Base
    #23 GregP507, Jul 11, 2014
  4. GregP507

    GregP507 Senior Member

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    2012 Prius Plug-in
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    Well, here it pure and simple. I fell asleep in my car with the radio on.
     
    #24 GregP507, Jul 11, 2014
  5. Ajwatuc

    Ajwatuc Junior Member

    Joined:
    May 14, 2013
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    Vehicle:
    2010 Prius
    Model:
    II
    Why not take option two apart and modify the plastic plug to hold the screen


    2010 Prius
    1973 cb500
     
    #25 Ajwatuc, Jul 12, 2014
  6. thordehr

    thordehr Member

    Joined:
    Aug 4, 2013
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    Location:
    Los Angeles
    Vehicle:
    2010 Prius
    Model:
    III
    Well, a few weeks ago I noticed voltage was in the 11 range when I had never seen it there before. It recovered and was in the normal high 13 to low 14 V range while in Ready and running mode. I left town for a couple of weeks, jumped in and it got me home no problem. A couple of days later I went to 'start' it and the dash went all christmas tree on me with the voltage down to about 8 volts. Couldn't get it to do anything past that. I pulled the battery and it appears to be the OEM battery from 2010.
    No swelling or obvious damage, so I threw it on a battery tender plus to see if I could get it's voltage up. Took about 24 hours to get it to a float/maitanance charge level. I decided not to reinstall it.

    In the meantime I ordered an Optima Yellow Top through Amazon. I topped off the charge before installing it. Works as expected with no fitment issues. There's even a hole in the top of the case to transfer the plastic vent tube elbow from the OEM battery. (Even though these batteries are sealed and don't typically vent or breathe.) Nice feature for them to add to retain the stock vent tube in it's original routing.

    My mistake was ignoring the voltage being out of range that one time. That was my one warning and a signal to order a new battery. It would have been in hand by the time I needed it. I had read in the forums that 5 years is a pretty common lifespan for the OEM battery and that's why I put in the voltage monitor in the first place since I was getting close. My MPG has always been pretty good if I drive carefully and my longest trip is typically 14 miles, so I don't expect to see the jump in MPG that some have reported with a 12V battery replacement.

    All that said, I now have a 12V battery that is apparently charged but I don't have confidence in that is free to anyone in the LA area before I decide to recycle it.
     
    #26 thordehr, Aug 25, 2015
    bisco likes this.
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