When Does the 12-Volt Battery Charge?

Discussion in 'Gen 3 Prius Technical Discussion' started by Yaesu, Jan 21, 2017.

  1. Yaesu

    Yaesu Junior Member

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    Since the ICE doesn't run full time, does it charge the 12-volt battery or is it charged by the drive battery? I ask the question because I am running both a ham radio and an electric cooler directly from the battery. The cooler draws about five amps continuously. Will the 12-volt battery stay fully charged when driving the Prius?
     
  2. bisco

    bisco cookie crumbler

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    yes, it charges all the time the car is in ready. the engine charges the hybrid battery, and the hybrid battery charges the 12v through the inverter/converter.
     
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  3. Yaesu

    Yaesu Junior Member

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    Do you know the rate (amperage) at which the 12-volt battery is being charged. My concern is that it is being charged at less than the amperage being drawn by the electric cooler and over a period of time even when the vehicle is being run, the battery will loose its charge.
     
  4. bisco

    bisco cookie crumbler

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    i don't. i would think if you're pulling too much, the fuse would blow?
     
  5. Yaesu

    Yaesu Junior Member

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    What fuse?
     
  6. bisco

    bisco cookie crumbler

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    the one controlling the power outlet. where are you plugging in the cooler?
     
  7. Yaesu

    Yaesu Junior Member

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    I am not using a power outlet. I wired my own cigarette lighter type socket directly to the battery, protected with a 7.5 amp fuse. I am concerned that the constant power requirement of about five amps might be too much for the charging system.
     
  8. bisco

    bisco cookie crumbler

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    i think 1000 watts or so. if you look through the threads where people use an inverter off of the 12v for emergency house power, there should be some good info there.
     
  9. jdenenberg

    jdenenberg EE Professor

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    The charging system can handle 100 amps (minus the existing load from the car accessories). You don't want to blow the 100 amp Fusible link so stay below 80 amps. The auxiliary power outlet can get hot if you pull 4-5 amps. So if that is your connection, take care to limit the current drain. I have run a thermoelectric cooler on lonh trips quite often in my 2004 Prius and the power outlet (AKA cigarette lighter) got warm, but delivered the 4 amps the cooler required.

    JeffD
     
  10. Prodigyplace

    Prodigyplace Senior Member

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  11. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    at 15:10 he begins discussing the 12 volt system, he is done with it by 18:00, he does not give any amperes, sadly.
     
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  12. Yaesu

    Yaesu Junior Member

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    Based on the responses and additional reading, it appears that under typical driving conditions (no high speed fan, rear window defroster, headlights, windshield wipers) it appears that there is sufficient charging power from the drive battery to charge the 12-volt battery to run the cooler. I will install a digital volt meter for a while to monitor the 12-volt battery.
     
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  13. bisco

    bisco cookie crumbler

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    all the best!(y)
     
  14. Yaesu

    Yaesu Junior Member

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    Thanks for your comments and help.
     
  15. bisco

    bisco cookie crumbler

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    pleasure.
     
  16. szgabor

    szgabor Active Member

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    I have an inverter to power some part of the house directly connected to the 12V battery (which is actually at about 13.6 V or so while in READY mode) the car can provide around 1000W constantly safely (with the right wires used) (tested 900w resistive load for several hours + the inverter loss) so 5amp is on the "12V" side is OK.
     
  17. szgabor

    szgabor Active Member

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    The power is NOT coming from the 12V battery while your car on READY (maybe a little buffer for current spikes when cooler starts). The car 12V bus is designed to be powered by the DC/DC converter when the car is in READY mode. There is main fuse for this right at the point of feed from inverter. (search PS for it )
     
  18. Yaesu

    Yaesu Junior Member

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    I am now confused. My power connection to the cooler is on the 12-volt battery. Is that battery being charged sufficiently to replenish the approximate five amps. that the cooler draws.
     
  19. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    My advice, never draw any current from the 12 volt system unless you are in Ready. The battery is very small and will not survive a drain when not ready. When in Ready, the battery is being charged, your power is supplied by the inverter.
     
  20. Yaesu

    Yaesu Junior Member

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    Ok, so I should simply unplug the cooler when parked. I haven't yet, but the total time away has been less than a half hour. I think the voltmeter will help determine the state of charge of the battery.
    Thanks
     
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