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Oops, left door open, drained 12V battery too much

Discussion in 'Generation 1 Prius Discussion' started by Optimus, Apr 20, 2009.

  1. Optimus

    Optimus Member

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    Oops, we (ok I) accidentally left a door open on the 2002 Prius and it wasn't discovered for a couple days. The dome light had been turned off, so the 12V wasn't completely dead, but the dash lights were dim and there wasn't enough juice to start the car.

    So, what's the preferred method to charge the battery? In the car? Remove from car?
     
    #1 Optimus, Apr 20, 2009
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I have a 2004 GenII so I can only speak from that perspective.

    I drained my battery in the winter which I felt was even worse due to the cold weather so I went to my friendly Sears store and bought a trickle charger. I hooked it up - still in the car - and let it charge. That was a few years ago and I'm still on the same battery.
     
    #2 TonyPSchaefer, Apr 20, 2009
  3. Optimus

    Optimus Member

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    I forgot I had a trickle charger. I should try that. Now, if I can only find it. I have a regular battery charger that will charge as low as 2A, but I don't want to risk ruining anything. I suppose my best bet is to remove the battery and charge outside the car.
     
    #3 Optimus, Apr 20, 2009
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you can set your regular battery charger to a 2A setting, then that should work well.

    To be ultra safe you can remove the battery physically, but IMO it would be good enough to just disconnect the negative terminal connector first.
     
    #4 Patrick Wong, Apr 20, 2009
  5. Optimus

    Optimus Member

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    Fixed. I removed the battery and ran it at 2 amps on the charger for 2 hours and it worked like a charm. Thanks!
     
    #5 Optimus, Apr 20, 2009
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Glad that this helped. However, 2A x 2 hours = 4AH. Since the capacity of the battery when new is 28AH you haven't provided much charge into the battery. As your battery is 7 years old its capacity is probably more like 15 - 20 AH at best, however the point remains that your battery still needs more charging.

    Hence I suggest that you leave the car READY at least for 3-4 hours or else take a drive of that length in the near future, to make sure the battery is charged up to its full capacity.
     
    #6 Patrick Wong, Apr 21, 2009
  7. Optimus

    Optimus Member

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    The car has already had that much driven on it in the last couple of days, without issue. I don't know if the battery is original to the car or not, so I can't say for sure if it really is 7 years old or not. Either way, I'm likely going to replace it before winter just to be safe. I couldn't find any kind of date code on the battery.
     
    #7 Optimus, Apr 22, 2009
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