gen1 prius 12v battery won't charge

Discussion in 'Generation 1 Prius Discussion' started by co_otter, Aug 24, 2019.

  1. co_otter

    co_otter New Member

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    Hi all!

    A little background - I bought this 2003 Prius from a friend for $600 knowing it had a bad traction battery and bad 12v battery. I replaced both and the traction battery has been great. For the 12v battery I decided I didn't want to mess with aftermarket "upgrades" and just bought a battery from the local Toyota dealership as a direct replacement (cost me like $200, oof!).

    The car ran fine and started fine for a couple weeks but then we let it sit for about 3 weeks. Now the 12v battery doesn't seem to want to hold a charge.

    The car will start right up with my jump box, no problem, and it'll run normally - no codes, even with the engine shutting off at stop lights and whatnot... but when I shut it off, it won't start back up again.

    Did I get a bad 12v battery from the dealership?
    Is there something else wrong?
    Is the car incapable of charging the battery if it gets fully drained? Do I just need to remove it from the car and charge it with a charger?
    How can I determine what's going on?

    Thanks all!!
     
  2. sam spade 2

    sam spade 2 Senior Member

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    Have you posted this exactly same question somewhere else in the last couple of days ?

    You need a voltmeter to see exactly what is going on.
    Hopefully it is just a bad connection at one end of one of the main 12 V battery cables.
    The "far" end of the negative cable where it connects to the frame or body is a common point of failure.

    But then, even new things fail occasionally and the battery itself might be bad.
    The converter that charges the 12 V could be bad.......but that is not likely since it continues to run after started.

    A voltmeter or a shop visit will be needed to find out what the problem really is.
     
  3. bisco

    bisco cookie crumbler

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    1) possibly

    2) possibly

    3) yes and yes

    4) charge the battery and see if it holds close to 13 volts with no load.

    turn the headlights on, and record the voltage minute by minute fro 10 minutes

    the battery has a full warranty for two years
     
  4. co_otter

    co_otter New Member

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    awesome! Thanks to both of you and thanks for such a quick response!

    1.) I didn't write this question elsewhere - sorry if it's a repeat of someone else's question that I missed!

    2.) I took the battery out of the car this afternoon and hooked it up to my charger in the garage... I'm going to let it trickle/maintain overnight just to make sure and try it again tomorrow... will update.

    I can't find my voltmeter but perhaps I should look harder ;) If not I'll take it to an autozone or something and have them do a load test on it.
     
  5. ronlewis

    ronlewis Member

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    I can't confirm yet how long these WalMart lawn mower batteries work since I've only had them a few weeks and not driven the cars much, but for $22 they don't have to last long, and they have a 6 mos warranty, and WM is great about replacing batteries under warranty - most of the stores don't even test to make sure it's no good - they just tell you to go get a new one from the store. So take yours in at 5 mos and replace it and you get a year for $22.

    I do know that they don't have much storage. I left the trunk open over night and just that little light drained the battery enough that I had to jump it. The guy who recommended them (can't recall if it was here or on the Yahoo Group) says he got his wife one of those small battery jump devices to carry with her in case it ever runs out, and that sounds like a good idea. Heck, you could pick up a couple of extra WM batteries at that price and carry them in the trunk with jumper cables.
     
  6. Brian in Tucson

    Brian in Tucson Active Member

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    You don't need to remove the battery from the trunk to charge it. The chassis connection for the negative wire is under the carpet near the battery. Just unscrew the fastener with a 10mm wrench and connect a charger. After charging overnite at 2 or 3 amps, it should read 14.2v. If it's below 12v, like say 11.8, you have a defective battery, one cell is dead. I ran into this on a jetski with a very new agm motorcycle battery. Not worth trying to return it to Chrome Battery, so I bought a new one. Lots of computerized ignitions require a minimum of 12v to even try to start.

    Download the Harbor Freight app, there will be a coupon for a free multimeter. They're cheap but they do work. And you can get a load tester for about $15 and it works well, too.

    I wouldn't carry a bunch of Walmart batteries unless they are sealed AGM. Wet cell batteries can tip over and leak acid, which is not an approved use. If your battery is NG, take the car back to the dealer with the service receipt and ask them to check it out. You've certainly spent enough to warrant some service from them.

    Note, if you're gonna let it sit for a while, put an automatic trickle charger or a battery tender on it.

    BTW, 3prongpaul at Boulder Hybrids is a good place to take your Denver based hybrid. A good guy!
     
    #6 Brian in Tucson, Aug 25, 2019
    Last edited: Aug 25, 2019
  7. sam spade 2

    sam spade 2 Senior Member

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    And the rest of the story is..............
    You don't have to disconnect ANYTHING to charge the battery.
    Just connect the charger to the battery posts.......or to the jump point and a good ground and come back the next morning.
     
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