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HV discharge at night.

Discussion in 'Gen 2 Prius Technical Discussion' started by aminorjourney, May 31, 2008.

  1. aminorjourney

    aminorjourney Mum to two prius!

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    Hi everyone.

    I'm pretty sure that Velma's HV battery is discharging at night. for the past few days I've got into her in the morning and her battery is on two or three bars - but when I pull up it's a few bars from being full.

    Is it just me, or is the HV battery undergoing self-discharge at night?

    Tonight I plan to drive her and leave her with a pretty full battery, noting down how many bars there are. Then tomorrow we'll see if she's discharged again, or if it's just me being paranoid.

    After a drive earlier I found that her HV battery was warmer on the right side than the left. I wonder if some of the cells are going.

    She's an '04 with 66,700 miles on the clock. Do these symptoms sound familiar or???

    Finally, is there anywhere safe to take HV measurements of the battery? I wish I had CAN view now so that I could actually get a fairly detailed HV voltage and estimated SOC!

    Thanks,

    Nikki.
     
    #1 aminorjourney, May 31, 2008
  2. Bobwho

    Bobwho New Member

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    After programming the Scan Gauge II will give you the battery voltage and read the SOC with a numerical read out.

    IMO any one driving a Prius needs more instrumentation. And you need the ability to reset any codes that may come up. I was once stuck and only the scan gauge allowed me to get my vehicle moving. It may never happen to you but if it does...
     
    #2 Bobwho, May 31, 2008
  3. qbee42

    qbee42 My other car is a boat

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    The question comes down to whether your HV battery is discharging, or whether the battery SOC display is misreading the actual SOC. Determining how much charge remains in a battery isn't as easy as a float gauge in a fuel tank. Now that I think about it, the Prius doesn't do all that well with the float gauge either. There is a bit of hand-waving that goes on with the SOC reading. As such, it often varies a bit overnight. A couple of bars is fairly normal. More than that sounds suspicious.

    Tom
     
    #3 qbee42, May 31, 2008
  4. aminorjourney

    aminorjourney Mum to two prius!

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    Thanks guys. I want to make sure everything is hunky dory before I go anywhere near any phev mods.

    My Ev has a really good soc meter so I'm not quite used to the vaguness of the proud one yet!
     
    #4 aminorjourney, May 31, 2008
  5. qbee42

    qbee42 My other car is a boat

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    Does your EV use lead-acid batteries? SOC is lot easier with lead-acid than with NiMh.

    Tom
     
    #5 qbee42, May 31, 2008
  6. David Beale

    David Beale Senior Member

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    Are you aware that the HV battery is completely disconnected from the car when you turn the car off? There is a relay in the battery "box" that disconnects both battery output lines.

    There have been complaints from other owners of the SOC meter being different (lower) in the morning as well. I suspect it's caused by the battery being cooler. I don't look at that readout much as it's not very accurate.
     
    #6 David Beale, May 31, 2008
  7. aminorjourney

    aminorjourney Mum to two prius!

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    HI Tom and David,

    No, my EV used Lithium Ion. I guess my BMS (which was over £500) was probably rather complex!

    But thanks for your reassurances about the SOC meter. I'm glad that it's common. I can stop worrying about it! ;)

    Yes - I knew about the HV relays.. There are three if I remember correctly, right?

    Nikki.
     
    #7 aminorjourney, May 31, 2008
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes... One switches the negative line. One switches the positive line and places a current-limiting resistor in series, used upon initial start-up. The last relay bypasses the resistor, after the inverter capacitors have been charged up.
     
    #8 Patrick Wong, May 31, 2008
  9. aminorjourney

    aminorjourney Mum to two prius!

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    That's what I thought - The two on the positive side help eliminate the horrible arcing you'd get. I do the same thing when hooking up my 43V, 100AH battery pack in my City El. The only difference is that I put a resistor in series by hand until the controller has had a chance to charge up the capacitors it has to prevent high current sparking...
     
    #9 aminorjourney, May 31, 2008
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