Anybody tried to jump start using low power source ?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by kensiko, May 1, 2013.

  1. kensiko

    kensiko Member

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    Since there is no starter and the 12V is only needed to power the computer and accessories, I wanted to know if anybody tried to jump start the prius with a 1 A power supply or a few C or D batteries.

    I suppose I could try it, but I would need to disconnect my 12V battery. If this works, I could just keep 8 C or D batteries in my car with a case that would allow them to connect together in series, so the day my 12V batteries dies, I will not be in trouble that much.

    If it works with AA batteries it would be even better.
     
    #1 kensiko, May 1, 2013
  2. jdenenberg

    jdenenberg EE Professor

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    The 12v battery needs to be able to supply about 20 amps for a few seconds to run some pumps. After that, only a small current is needed. I'm afraid that at maybe Alkaline D cells (8/9 of them in series) or better NiMh/NiCad (10/11 C or D in series) or hobbyist LiOn (4 in series) would be required. I just have a portable jump battery (Lead-Acid) with me just in case (only used to jump other cars to date).

    JeffD
     
    #2 jdenenberg, May 1, 2013
  3. kensiko

    kensiko Member

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    I see, 20 Amps is much higher than I thought. I have a portable lead-acid battery but it doesn't keep its energy, I would need to buy another one. It's heavy too.
     
    #3 kensiko, May 1, 2013
  4. hlunde

    hlunde Member

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    The ultimate irony:

    Your Prius has a dead 12v battery, you need 1200 joules to start it (20 amps for 5 seconds), your vehicle has perhaps half a million stored joules in its traction battery, but they are not accessible for this purpose.
     
    #4 hlunde, May 5, 2013
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  5. kensiko

    kensiko Member

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    True, I bet a high quality DC 200V to 12V converter would be much more reliable. They make veys small switching power supply with many amps now, I don't know why they thought that the car would be better with a 12V battery.
     
    #5 kensiko, May 5, 2013
  6. jdenenberg

    jdenenberg EE Professor

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    The issue is safety!

    The Traction battery (HV) is split in half (reduces dangerous voltage level) and disconnected from the rest of the vehicle when you shut your Prius down. That way emergency workers at accident sites and your mechanic can work on your Prius without the risk of electrocution.

    Toyota could have provided some 12v battery monitoring electronics (warn if low SOC), protection from full discharging (disconnect before full discharge) and reverse polarity jump protection (protect the vehicle from sloppy jumping) to eliminate most of the problems that Prius owners have had with their 12v battery, the only down side would be some added expense.

    JeffD
     
    #6 jdenenberg, May 6, 2013
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  7. hlunde

    hlunde Member

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    Am I correct to assume that the HV disconnect is under the hood, so that there is an always-live HV cable running the length of the vehicle?
     
    #7 hlunde, May 6, 2013
  8. jdenenberg

    jdenenberg EE Professor

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    No, The disconnect is done by a set of relays (AKA solenoids) in the HV battery. In the Gen2 Prius, the disconnect hardware is inside the housing near the safety switch on the left (looking at it from the hatch opening).

    JeffD
     
    #8 jdenenberg, May 6, 2013
  9. hlunde

    hlunde Member

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    That's good to know.
     
    #9 hlunde, May 6, 2013
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