Prius Prime 12 volt VOLTAGE

Discussion in 'Prime Main Forum (2017-Current)' started by Flagmaster, Aug 6, 2019.

  1. Flagmaster

    Flagmaster Junior Member

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    Can anyone explain to me why in the prius prime, the 12-volt rail that seems to run everything 12volts in the car seems to switch voltages while driving? Iv has seen it go as low as 12.7 and as high as almost 15. Im attempting to run a power interver in the car at approx 1000 watts rms, and the poor thing gets so confused when the "battery voltage input" drops below 13. Lower input voltages cause the inverter to have to work harder to maintain 120 vac out, and that can make it run very hot.

    Its a 3000 peak power, 1500 continues, and Im trying to pull around 600 up to 1000 watts off it.

    Is this voltage change to help preserve the 12volt lead acid battery life?
     
  2. jb in NE

    jb in NE Senior Member

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    There are several threads on this issue. This is normal on the Prime - when you first start up it runs a pretty high voltage (14.7 if I recall) which quickly ramps down to mid 12's. The 12V battery doesn't carry much load - the DC-DC converter is carrying the vehicle loads and only has to put a bit of charge back in the 12V battery to restore it to full charge.
     
    #2 jb in NE, Aug 6, 2019
    Last edited: Aug 6, 2019
  3. Rob43

    Rob43 Senior Member

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    Trust me when I say there have been many many discussions about 12v battery fluctuations and what to do about it.

    Unfortunately, I don't know of any solid answers to your inverter dilemma.

    **************************************************

    If it were me:

    I would buy an Odyssey PC680* and run it as a buffer battery, it would go between the OE 12v battery & your inverter. The great thing about Odyssey batteries is they are military grade and can be mounted in any possible position because they're 100% sealed & can Never leak or vent.

    I would use at least 8 AWG wire as a bare minimum from the OE 12v to the buffer battery. Also, twist the wire going from the battery to the inverter with multiple twists, this cuts down on RF interference.

    www.odysseybattery.com/Specs/ExtremeSeries


    Rob43


    * Or similar.
     
  4. Elektroingenieur

    Elektroingenieur Senior Member

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    It’s by design, for energy efficiency. The operating principles are the same as on fourth-generation Prius cars, which I discussed in post #4 and post #18 of a previous thread.
    You haven’t mentioned the duration or duty cycle, but I think it’s safe to say that Toyota didn’t design the low-voltage electrical system on the Prius or Prius Prime to supply an added load of this magnitude.

    Keep in mind that the maximum output current of the DC-DC converter is 100 A, at 11.0 to 15.0 volts DC, according to New Car Features (more info). Toyota does offer a 1500 W inverter as an option in Japan, but it’s connected to the high-voltage system, usable only when the car is parked, and—most important of all—controlled by the Hybrid Vehicle ECU, as described in my May 2017 posting.

    An added battery, as @Rob43 kindly suggests, wouldn’t help if the problem is long-term energy balance. The battery can temporarily provide additional current, but it can’t do that for long, and it must then be recharged. Over a long enough period of time, your inverter and the other electrical loads can’t take energy out of the system at a greater rate than the DC-DC converter is putting energy into it. That’s limited by its design and controlled by Toyota’s software, not easily modified.
     
  5. Rob43

    Rob43 Senior Member

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    ^ Agreed, this is not a long term solution for hours of daily operation, it is a short term solution for daily use. The buffer battery would help as a short term stabilizer, but then would need to be recharged by the electrical system for the next event.

    You certainly can't take more from the system than the system is supplying,.....and get away with it.


    Rob43
     
  6. ChapmanF

    ChapmanF Senior Member

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