I have an idea...

Discussion in 'Gen 5 Prius Accessories and Modifications' started by Paul Gregory, Sep 21, 2025 at 1:59 AM.

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  1. bisco

    bisco cookie crumbler

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    did you get a jump pack with a dead battery override switch?

    the battery has to close relays as well as boot computers. idk how much current is needed.
     
    #41 bisco, Sep 22, 2025 at 9:08 PM
  2. ChapmanF

    ChapmanF Senior Member

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    It's easy to overlook a lot of the draws on the 12-volt battery in the process of going READY.

    The process starts out the same as IG ON, with power to all the car equipment that gets power in IG ON. That includes a couple dozen computers, the instrument panel, some pumps, and so on, also extra things like the wipers or seat heaters if they were left on when the car was shut off.

    As soon as the HV control ECU has completed its checklist and decided it's ok to close the battery relays, the DC/DC converter comes online and takes over supporting those loads, but they were all on the 12-volt battery for the second or so before that happens.

    The battery relays aren't an especially significant part of that load, just another small part of the total.

    In my generation, the brake accumulator pump can be one of the larger loads active during that time. But I'm not positive gen 5 does the brakes the same way.
     
    #42 ChapmanF, Sep 22, 2025 at 9:22 PM
  3. bisco

    bisco cookie crumbler

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    that must be why my 12 had auto off seat heaters
     
    #43 bisco, Sep 22, 2025 at 9:23 PM
  4. ChapmanF

    ChapmanF Senior Member

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    oh, they changed that? in my '10 the seat heater switches are plain mechanical switches. on is on.
     
    #44 ChapmanF, Sep 22, 2025 at 9:25 PM
  5. Paul Gregory

    Paul Gregory Senior Member

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    I never use seat heaters. They make my butt itch.
     
    #45 Paul Gregory, Sep 22, 2025 at 10:09 PM
  6. Hayslayer

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    How many people need to tell you that YATAH before you believe it?
     
    #46 Hayslayer, Sep 22, 2025 at 10:20 PM
  7. Paul Gregory

    Paul Gregory Senior Member

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    It seems that draining the battery intentionally is not so easy. I left the ACC on, but when I came back an hour later it was turned off and the battery was at 12.6 volts. The booster however, came on when I plugged it in, as indicated by a green light.
     
    #47 Paul Gregory, Sep 22, 2025 at 10:22 PM
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