12v battery dead/recharge, neg. terminal sparks

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Brian M LaFrance, Aug 5, 2021.

  1. Brian M LaFrance

    Brian M LaFrance New Member

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    Hello, just bought my first Prius last Sunday, a 2008. Test drove fine, etc. The previous owner said it was her mom's who passed away, and was sitting for a while. Well, not 3 days later, we go to drive it, and it is completely dead. After digging, figured it might be 12v battery. I found some vids on how to recharge, and ran a trickle charge through it for a day. The video I watched said to not do this at the front battery terminal, but directly on the battery in rear of car, and to disconnect the neg. terminal first. So I did. When I go to reconnect that terminal now, I get a spark. Wondering how to proceed? Rubber gloves? and will I do damage by reconnecting ? and if I really needed to disconnect that terminal, and if I really need to do this directly on battery? I'm pretty sure I need to replace this battery, but, seems this might be a recurring thing, and it was a bit of a hassle to get to the battery. THanks much.
     
  2. SFO

    SFO Senior Member

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    Before reconnecting the neg cable, check the date code on the 12 battery as it could be the original and will need replacing.

    How many hours per week are you currently driving?

    FYI : your posts are being moderated until you've posted 5 times.
     
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  3. dig4dirt

    dig4dirt MoonGlow

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    As long as you are trying to reconnect the neg cable to the neg post, a spark is ok and normal

    If the battery is older as SFO mentioned, more than likely this will cause problems.
    And if it has been sitting a while, then time to change it anyway. That could mean a year or more huh?

    Yes use gloves if you must, but not necessary.
     
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  4. ChapmanF

    ChapmanF Senior Member

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    If the sparking on reconnection of the battery were going to harm anything, you already would have when you saw it spark.

    There are electrical loads in the car, and some of them even contain power regulators with capacitors; it's not very surprising to see a bit of a spark when restoring the connection.

    A charger can just as easily be connected to the jump points in front. There's nothing between that and the battery itself besides a fat wire and a large fuse. Naturally, it can carry the current of an actual jump from another car battery, and the small current of an appropriately-sized charger is scarcely anything in comparison.

    If you have a very smart charger that would be confused by having car loads present at the same time, then you might want to disconnect the battery, but the easier way in a Gen 2 is just to squeeze and unplug the large cable connection at the battery + terminal. No fussing with a wrench.
     
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  5. Brian M LaFrance

    Brian M LaFrance New Member

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    awesome, thanks much for the replies!
    SFO: we just got the car, so, have driven it about 2-3 hours I'd say. No telling how much it was driven in last year.. not much, I'm guessing: it's a 2008 with about 83k miles.
    So, from reading other threads, seems the least hassle way of getting a new battery (albeit not cheapest) is from the Toyota dealer?
     
  6. edthefox5

    edthefox5 Senior Member

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    There's 2 black cables plugged in to the assy on the top of the 12 volt battery assy. One thick one one smaller one. If you get a little screwdriver and and press there release lock clips they pull right out then the 12 volt battery is disconnected from the car. No sparks.

    I've been charging the 12 volt battery on my bought new 07 for 14 years. Its the front jump point its designed to jump or maintain the battery. Don't have to disconnect anything. Stop watching that video its nonsense.
     
  7. sam spade 2

    sam spade 2 Senior Member

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    AND if the charger you have really IS a "trickle charger", you might need to leave it connected for DAYS to get a full charge.
     
  8. Brian M LaFrance

    Brian M LaFrance New Member

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    Yes, Sam Spade 2, had to leave it for a full day to get a full charge.
    And thanks edthefox5, will never watch that vid again :)
     
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  9. ChapmanF

    ChapmanF Senior Member

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    If there'd be a spark when reconnecting on the − side, there'll be a spark when reconnecting on the + side. The electrons don't care.*

    But those plug-in connections on the + side are easier to make, no fussing with a wrench, and kind of enclosed. More like plugging in a regular plug. So maybe you'll be less likely to notice a small spark.

    The smaller of the two is just a voltage-sensing connection that runs back to an input on the car's DC/DC converter. You can unplug it too for completeness, but unplugging the fat one takes the loads off the battery.



    * "Elk don't know how many feet a horse has!"
     
  10. Brian M LaFrance

    Brian M LaFrance New Member

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    thanks ChapmanF.
    Hooked up the battery this morning, took it for a ride for a while.
    I had to insert the key fob into dashboard to start. and after taking it out, there is a car/key icon flashing on dashboard.
    I'm guessing I need to reset the key somehow?
     
  11. Brian M LaFrance

    Brian M LaFrance New Member

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    Is it as simple as pressing the key reset button while car is on, making sure it is in the out position? thanks
     
  12. Brian M LaFrance

    Brian M LaFrance New Member

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    answered my own question: apparently, it *was* that simple. Reset the key, all is well. thanks much y'all :)
     
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