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Auxiliary battery charging

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by hilfordjames, Jan 31, 2023.

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  1. hilfordjames

    hilfordjames New Member

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    If the auxiliary battery is flat due to interior light being left on as an example, can the hybrid battery be used to charge the auxiliary to then start the car?

    I was told today that instead of putting your foot on the break and pushing the start button, you can simply keep all feet off pedals and push the start button and in this mode the relay will open and allow the hybrid battery to charge the auxiliary start battery if you wait long enough.

    In the past I've jumped the auxiliary battery but not having to connect a jumper and using the cars stored electricity would be a better option.

    I was also advised today NOT to jump the auxiliary battery and instead clip the red jumper lead onto the red post within the fuse box under the bonnet and the black negative onto the engine - this way is reduces the risk of a voltage spike going through the electrical system.
     
    #1 hilfordjames, Jan 31, 2023
    Last edited: Jan 31, 2023
  2. rjparker

    rjparker Tu Humilde Sirviente

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    No it won't work. Once you achieve Ready, the hv battery through the inverter will charge the 12v battery at a high rate.

    The jump point under the hood is just more convenient. It is actually closer to expensive electronics. Jumping under the hood is easier from an access perspective especially when the electric hatch operator is not working. Reverse jumps are possible from either place.
     
    #2 rjparker, Feb 1, 2023
    vvillovv and Air_Boss like this.
  3. Air_Boss

    Air_Boss Senior Member

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    You’ll have to use the physical key to open the drivers door to open the hood.
     
    #3 Air_Boss, Feb 2, 2023
  4. Louis19

    Louis19 Active Member

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    If you do what you were told (see quote) you will depleate your 12v battery . To allow charge you must put your foot on the brake and push the start button,hense putting the car in READY allowing the traction battery to charge the 12V battery via the DC to DC converter in the inverter module.

    But if you cannot acheive Ready , well you will need to charge the 12 v battery in an other manner
     
    #4 Louis19, Feb 2, 2023
    Last edited: Feb 2, 2023
  5. vvillovv

    vvillovv Senior Member

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    @hilfordjames there is a kinda easy way to test the theory of [ you "can / can not" charge the 12 volt AUX battery by pressing the On button once and waiting long enough ] .

    Open the car door - open the hood / bonnet or hatch to access the 12 volt AUX battery - take a voltage reading on the AUX battery terminals using a voltmeter - get back in car and press the On button once without pressing on the brake pedal - start taking voltmeter readings on the AUX battery terminals until you get an answer to the theory.
     
    #5 vvillovv, Feb 2, 2023
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