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Jump starting from a Prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PA, May 13, 2013.

  1. PA

    PA Member

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    Yes, it works.

    That was the answer to my question this morning, and in case it's your question too, I thought I would post my experience (since I couldn't find another post here on Priuschat on the same topic, although I found scattered info elsewhere).

    Although the 12V battery is in the back, the + battery terminal is under the hood on the right side (pry off the black fuse block cover on the right, and lift the red + cap). Neg. clamp can be attached to a bolt behind wiper fluid reservoir on left, but I ended up attaching the neg. clamp to a bolt on top of the engine since my cables wouldn't reach that far. Pictures are in the manual showing locations of terminals. Other leads went directly onto terminals of dead battery.

    Depress accelerator pedal of Prius to get gas engine to kick on, and keep it on for 5-10 min. to charge dead battery. (5 min. might be enough.)

    Detach jumper cables before attempting to start dead vehicle. Some posts claimed manual states leaving it connected would damage Prius (although the only thing I could find was about jump starting the Prius itself, not the other way around).

    Anyhow, that's what I did, and it worked. I hope this helps someone.
     
  2. edthefox5

    edthefox5 Senior Member

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    To get the black plastic fuse cover off just depress the bottom of the box along the top of the box and gently pull top cover off.
    Right above the fuse box at the top of the shock tower is a nut/bolt used for neg connection.
    Under the red plastic cover is a vertical metal tab to connect your + cable.

    And never ever use your Prius to jump start another car.
     
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  4. RobertK

    RobertK Member

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    If you are going to use a Prius to jump start another vehicle, just leave the Prius OFF. If you make the Prius READY, the car will feed a constant 3 amp charge to the 12 volt battery from the inverter with or without the ICE running. The 3 amp charge is trivial when compared to what the 12 volt battery stores and what a conventional car needs to start. A conventional car alternator can put out in excess of 100 amps, which might help when starting one conventional car with another running car.

    If you rev the Prius gas engine while the car is is PARK the hybrid battery will actually quit charging until you take your foot off of the gas. This has no effect on the 12 volt battery. You can confirm this by looking at the MFD power flow screen.

    Personally, I won't ever jump start another car with my Prius, and I replaced my 12 volt battery at the first sign of a voltage drop just to reduce the possibility of needing a jump start down the road. I gave my son a jump start pack when he went off to college, and he has used it several times to start his friends' cars and his own car once when he left the glovebox door open for a week without driving the car. Jump start packs usually contain circuitry to help prevent improper connections and most of them have air pumps to help keep the tires properly inflated.
     
  5. PaulRivers

    PaulRivers Member

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    fyi, I found that turning on the heat to anything, and the inside fan to anything, often keeps the engine running to. Or try heat to max and fan to full on if the engine turns itself off.
     
  6. uart

    uart Senior Member

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    Hi PA. Technically what you did was to charge the other car's battery from the Prius rather than actually jump starting it. This is the safest option, but it requires that the other car's battery (apart from being discharged) be in reasonable condition.

    Even though 5 to 10 minute is not enough time actually charge the other battery, it can however give it a "surface charge" that is enough to crank it, as long as the battery is basically healthy.

    One important point though. You definitely DON'T need to run the engine in order to achieve this feat. The Prius 12V battery charging systems functions exactly the same way when the car is in ready mode, regardless of whether or not the engine is actually turning. So just leave it in ready and let the engine come on or off as it wishes, it will work exactly the same.
     
  7. Britprius

    Britprius Senior Member

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    It is a misconception that the Prius only charges at 3 to 4 amps.

    Having done some tests with partly discharged batteries with the Prius I have measured over 60 amps charging the battery. The DC to DC converter is capable of 100 amps.

    I know this seems wrong when the OEM battery clearly states on the top label "max charge 4.5 amps" but perhaps this is one of the reasons why the OEM battery does not last long once it has been fully discharged.

    John (Britprius)
     
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  8. uart

    uart Senior Member

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    Very true. You only have to measure the voltage to see that it will very rapidly try to bring it up to about 14 volts, during which time I expect it would deliver a similar charging current to the target battery as any regular alternator equipped car would.
     
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  9. Britprius

    Britprius Senior Member

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    I have measured 14.6 volts from the Prius charging system this with a battery only 20% discharged. I have every reason to believe it could go up to 14.8 volts but will confirm when my tests are complete. So I am sure your expectations are correct.

    John (Britprius)
     
  10. The Electric Me

    The Electric Me Go Speed Go!

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    I believe it is possible.
    But I agree with those that simply say never jump start from a Prius.
    It's one of those things where even if it CAN be done, I believe it shouldn't be done. The risk is just too great.

    It's nice to be the good Samaritan, but you're risking a lot of complicated electronics.

    Absolutely one of the first things I bought after buying my Prius was one of those compressor/jump start units. Great for maintaining tire pressure and also great if somebody asks me for a jump start. I can now do both, without any electrical connection to my Prius at all.