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12 volt battery question

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by CanyonKid, Feb 2, 2015.

  1. Mendel Leisk

    Mendel Leisk Senior Member

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    So for example, if you have a battery reading 12.6 volts, and a 16 milliamperes draw, is it not abnormal for it to be reading around 12.45 on 3-4 days sitting idle?

    It doesn't seem to continue linearly, ie: it seems to stabilize (or I'd like to think so), at that lower number.
     
  2. Easy Rider 2

    Easy Rider 2 Senior Member

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    Yes I think all of that could be considered "normal"......but somewhat marginal after only a few days.
    According to the SOC tables, that equates to a loss of 25% capacity and that is a LOT over just a few days.
    That is assuming a conventional flooded cell battery. If it's AGM, the prognosis is worse.

    The current drain may actually decrease after a few days too.
     
  3. CanyonKid

    CanyonKid Junior Member

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    Many thanks to everyone who answered on my post. Here's the bottom line at this point. I can drive over to elearnaid in 20 minutes and get a Yellow Top for $186 with $10 installation. OR I can get Toyota battery from the dealer, 15 minutes away, for $201 plus $120 installation. Or buy Toyota battery and install myself.

    There is apparently one other option per elearnaid, disconnect battery when I park at airport, but that's a non starter, I'm not gonna hook everything up again leaning over the back seat in the middle of the night trying to put the carpet cover somewhere and the plastic tray, etc, because I know from experience that when the battery is dead, there's no access to ANYTHING, except the front door, that's it. Oh, except you can unlatch the hood since it's manual.

    Elearnaid is "almost certain" that a fresh battery from him will sit for 16 days with no problem. Toyota dealer is also certain...that their battery sitting for 16 days wouldn't be guaranteed to start.

    So, my plan is either get the Yellow Top from elearnaid installed a couple of days before my trip, or park the car at airport and have AAA come start it again, then buy new battery after that. My feeling is toward AAA, because lets say the Yellow Top lasts great for say 14 days, then goes, I have a brand new battery that already discharged once when I had only driven on it for one day.

    Which way would you vote?

    TIA,
    Michael
     
    #43 CanyonKid, Feb 4, 2015
    Last edited: Feb 4, 2015
  4. Easy Rider 2

    Easy Rider 2 Senior Member

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    Either way is fine. Pick one.

    There is virtually no danger of a new battery going dead in 16 days......IF IT IS FULLY CHARGED TO BEGIN WITH.
    That's unless there is some kind of fault with your car of course.

    Have you called around to auto parts stores and other Toyota dealers ?
    That $125 installation fee is outrageous but the batteries do tend to be kind of expensive.
     
  5. CanyonKid

    CanyonKid Junior Member

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    I don't really feel the need to call around, $10 installation from a guy who does it all the time sounds fine to me from elearnaid. His free shipping is rolled into the price of his battery, but he does the $10 install to defray that cost for locals, good deal. And his batteries in stock were made in December, they're at full charge, any battery at the dealer will be from Japan or Indonesia, they gotta be at least 4 months old, coming by boat.

    Regarding quality control on Yellow Tops now made in Mexico, he says less than .5% of his customers have had any kind of problem.
     
  6. Easy Rider 2

    Easy Rider 2 Senior Member

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    OK I hope that works out for you.
    You just seem to be putting a LOT of trust in this guy.
    Hope it's not misplaced.
    It probably isn't; I tend to be overly cautious. That comes from being burnt too many times.
     
  7. CanyonKid

    CanyonKid Junior Member

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    I guess I am, but he's been around a long time, is a Prius owner (that's how he got into the battery thing), and in my brief searches here about elearnaid I didn't come across anything bad about the guy.
     
  8. GregP507

    GregP507 Senior Member

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    There seems to be many factors. Corrosion, moisture, phantom-drain and self-discharge all play a role, I'm sure.
     
  9. CanyonKid

    CanyonKid Junior Member

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    Parked for extended time in scorching Los Angeles heat in an unshaded parking lot too, maybe? Last trip it was over 90 degrees every day I was gone. Don't know if that affects the battery.
     
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    I'd be inclined to get the toyota battery and install myself. But I'd check voltage at the deslership, should be at least 12.6 volt. Then hook it up to a smart charger, let it run to completion. Then clean the posts and cables when doing the swap.

    It's pretty easy: disconnect neg cable first, and reconnect it last. All you really need is a 10 mm wrench. And fine sand paper, and/or a post cleaner tool. A 1/4" drive with 10 mm socket can come in handy.

    When tightening clamps, I don't have a torque wrench in that range, let alone compact enough. What I do is keep my hand maybe halfway along the wrench handle, and don't use much force.
     
    jdcollins5 likes this.
  11. macman408

    macman408 Electron Guidance Counselor

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    That's normal, especially if you measured not too long after turning the car off (i.e. less than 12 hours). There's something called "surface charge" - after the battery has been charged, there's a little residual charge on the plates of the battery that keeps the voltage elevated. If you put a load on the battery for a few minutes (like by turning on the headlights) or let it sit long enough, the charge will be used up powering the load, or dissipate into the battery (by the same chemical reaction that happens when you charge it), respectively.

    So most likely, 12.45V is what your car would read if you got rid of the surface charge before the 3-4 days. And that's a totally normal battery voltage; mine has read ~12.5V since approximately the day I got it, and the battery is still in fine shape (measuring the same 12.5V) 5 years later. And that's including one complete discharge that happened a few months into ownership, which doesn't seem to have had any lasting effects.
     
    Mendel Leisk likes this.