Prius C - Charging rate of the 12V auxiliary battery while idling?

Discussion in 'Prius c Technical Discussion' started by Mr. King Andrew, Jul 10, 2019.

  1. Mr. King Andrew

    Mr. King Andrew New Member

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    Does anyone know the exact output, in amps, from the Prius's charging system (I know it's not an alternator, but whatever functions as that) to the 12v auxiliary battery while the car is at idle?

    Is there some sort of datasheet that shows the charging output to the 12v battery at different engine speeds?

    Does the 12v battery charge at all while the car is "idling" but the engine isn't actually on?
     
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I can't point to any documentation to back it up, but I understand the DC/DC converter to be capable of supplying about 100A, and that it operates any time the car is in READY mode.

    EDIT: adding...

    I don't believe the converter cares about engine RPM at all. It's tapping the high voltage battery to make 12v on demand. The high voltage battery management ECU occasionally requests charging, and the engine starts and runs to accommodate as needed.
     
    #2 Leadfoot J. McCoalroller, Jul 10, 2019
    Last edited: Jul 10, 2019
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  3. Mr. King Andrew

    Mr. King Andrew New Member

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    Interesting. That's really high amperage for a car, which is what I was hoping to hear. Does that mean that, in theory, it should be possible to connect the 12v leads from the Prius (under the hood) directly to a larger 12v battery bank, which itself is connected to a power inverter, and basically use Prius as a ~1000w gasoline generator during a power outage?

    Not that Toyota would actually condone that... but....
     
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Most modern cars have 90-120 amp alternators.

    There are many threads about adding inverters to a Prius for emergency household power, been done many times. There used to be a nice kit that actually tapped the high voltage battery directly for much more AC power, but that manufacturer has quit the market.

    That said, there's still a lot you can do with the 12v bus.

    You aren't likely to be able to milk 1000w out of the 12v side. A Prius has more 12v ECUs and support electronics than the average car, so there's a bit less available to your proposed power system.

    It will be hard to beat the cost of an ordinary 1000w camping grade generator once you factor in a charging isolator, appropriate batteries, the inverter and all the bits you need for safe usage. A Prius-based setup can offer a few advantages over the genny. Fuel capacity & runtime is near the top of the list. The Prius burns cleaner, but a well kept Honda genny might beat it for actual fuel efficiency.

    @Terrell has a lot of experience in this space.
     
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