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Intermittent dead battery/relay?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by offgrid, Feb 16, 2010.

  1. offgrid

    offgrid Junior Member

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    Before calling Toyota I would like some feedback from you guys--while just 8 months old I started having problems with my 12 volt battery being dead once a month or so. Got advice here about locking, etc so as not to drain the battery. Despite that, it happened 4 more times, went to Toyota, they replaced what they said was a bad battery for free. Now it is happening again--new battery is a year old and the car has been dead 3 mornings this month.
    When we put the battery charger on it, it makes a clicking sound and lo! the battery comes up immediately into the green, drives fine, starts up again at my destination, etc. Is it possible that it has a bad relay or something? (it is < 2ys old, 12K on it--seems to go dead after sitting for more than one day) Thanks for any insights...
     
    #1 offgrid, Feb 16, 2010
  2. JimN

    JimN Let the games begin!

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    I wouldn't have tolerated this situation as long as you have. The replacement may still be covered under the original warranty, ask the dealer. If not, it had a 1 year unlimited mileage warranty.

    Trickle charge the battery. When you know it is fully charged get the voltage readings. If the battery isn't holding a charge it will need to be replaced. If something is discharging the battery then the dealer will have to diagnose the problem & fix it under warranty. If an aftermarket part or mod is the culprit then this will be on your dime. Good luck.
     
    #2 JimN, Feb 16, 2010
    1 person likes this.
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Since you say that the 12V battery won't accept a charge, yet it fails to start the car, then I would say that the 12V battery needs to be replaced again.

    It's possible that a relay is bad and is staying closed when it should be open. If you have a digital multimeter you could measure battery current when the car is IG-OFF (you'll have to lock the doors and keep the Smart fob well away from the car for an accurate measurement.) If the quiescent current draw is more than ~30 mA then I would suggest looking for an electrical problem.

    Also, it appears that you are not driving the car much with only 12K miles after 2 years - so you may want to use a battery tender or else hook up a battery charger 2x per month to keep the 12V battery in good shape.
     
    #3 Patrick Wong, Feb 16, 2010
    1 person likes this.
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