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Gen I Prius help needed

Discussion in 'Generation 1 Prius Discussion' started by rwhyde, Jun 19, 2012.

  1. rwhyde

    rwhyde Junior Member

    Joined:
    May 31, 2011
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    Location:
    Colleyville, TX
    Vehicle:
    2006 Prius
    Model:
    N/A
    I have an '01 Prius with 144K that I bought cheap as a project car a year ago. I've replaced the main battery with Gen II cells and it works well most of the time. My issue is it keeps killing the low voltage battery. I thought I had a bad battery from Toyota, it was less than 4 months old when I bought the car, so obviously they had this issue too. The battery was dead then and I charged it up and it would hold a charge but randomly go flat. I've checked it multiple times for draw and everything goes to sleep just fine when I am looking. I finally replaced the Toyota battery last month with a new Optima, thinking that I just had some sort of battery issue and would solve it once and for all. It worked well in normal driving for over 3 weeks and then bingo my son's wife heads off to work and the dash lights up. on Monday so she gets it around the block and back home. So today he calls and says it is totally flat and nothing lights up. I have seen teh car yet and don;t expect it to have codes left with this dead battery by the time I get back home from a business trip on Friday evening. So, I want to check the list wisdom here and see if anyone else had had a similar issue or can tell me what is controlling the low voltage battery drain. I assume at some point it just isn;t going to sleep properly and I need to replace whatever is controlling the sleep mode. Other ideas??
    Thanks,
    Wayne
     
    #1 rwhyde, Jun 19, 2012
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Check if the door might not close and leave the dome light on.

    Bob Wilson
     
    #2 bwilson4web, Jun 20, 2012
  3. vincent1449p

    vincent1449p Active Member

    Joined:
    May 24, 2004
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    Location:
    Singapore
    Vehicle:
    2012 Prius c
    Hi rwhyde,

    It may not be the Aux Bat draining, have you check whether the DCDC converter is charging it? Changing components without troubleshooting does not always work. You need to get a voltmeter to measure directly at the battery posts for about 14V in READY. If OK, switch off the car and use an ammeter to measure the drain current. Our NHW11 typically has about 35 mA when parked. hope this helps

    Vincent
     
    #3 vincent1449p, Jun 20, 2012
    usnavystgc and bwilson4web like this.
  4. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

    Joined:
    Jul 29, 2011
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    Location:
    Tucson, AZ
    Vehicle:
    2005 Prius
    Model:
    Four
    +1 on vincent's advice. While I was reading your post, the first thought that came to mind was the DC-DC converter not charging the battery. This would indicate a problem in the inverter. Measure it as he says and post the results here. From what you say, it sounds like when you charge/replace the battery, the car works fine for a while (about 3 weeks). That's probably just enough time to completely drain the 12v (since its not being charged). This is similiar to an alternator going bad on a regular car (runs fine until the battery drains), it just takes longer for the battery to drain on a hybrid.
     
    #4 usnavystgc, Jun 20, 2012
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