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2nd Dead 12v Battery in less than 1 month

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by DriverX5, Jul 24, 2019.

  1. DriverX5

    DriverX5 Junior Member

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    Hello,

    I've scoured the net and can't really find much of an explanation to my troubles. We have a 2007 Prius (no nav, yes JBL). A few weeks back we were mucking around in the car, and left the radio on for some tunes and had the windows up and down a few times, without the car on (but yes accessory mode?). Surely enough the 12v battery was dead within a half hour. When we investigated, we found it to be the original 2007 battery - quite impressive and not surprising that it must have just been hanging on by a thread all these years and we doomed it by ~20 minutes usage without the DC/DC charger kicking in. The voltage was down to like 5v. For kicks, I put it on the battery tender, but actually the model we have charges both 6v and 12v automatically, so the thing just said full charge at 6v thinking it was hooked up to a 6v battery (not that it would have mattered anyways as I am pretty sure anything below 11v is nonviable). We replaced the battery and all was well for a few weeks. I did not check the new battery voltage, nor did I check periodically the voltage after it was installed.

    Fast forward a couple of weeks, and after having left the car undriven for about a week, somehow the new battery has also died. The car was locked, out on the driveway. Totally unresponsive. A check of the new battery revealed it was down to around 6v as well. I'll be darned. No explanation for this one. No one left anything on, nothing was plugged in. Haven't noticed any electrical gremlins. Yet somehow this new battery is also a goner. Unfortunately I never measured the new one, I just assumed it was a good 12.5v+ fresh battery. It's entirely possible it was a dud, but it just seems so improbable. So we hooked up a spare 12v battery and started troubleshooting.

    With the car on, the voltage at the rear terminals increases to around 14V, leading me to believe the DC/DC charger is fine. I used my multimeter as an ammeter between negative on the spare 12v battery and the ground of the car. When we muck around with it, like have a door open or the like, it draws a few amps as I would expect. With me tucked in the rear, all doors closed, and car locked from outside via key, it sits between 1-2A for about a minute or two before finally dying down to 10-20mA. I would assume this is an acceptable value for parasitic draw while the car is closed and locked.

    Anyone know where to go from here before I lose another new battery?

    TLDR: original battery died fair enough, new one died not long after, DC/DC charger puts out ~14V and parasitic draw with car closed and locked around 10-20mA - what killed my new battery and will it kill my replacement new one?

    Thanks!
     
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  2. JC91006

    JC91006 Senior Member

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    sounds like you left something opened or light on to drain the battery again. A battery will drain if you let it sit and do nothing. The stronger the battery, the longer it'll hold the charge. Maybe the "new" battery you got has been on the shelf for years, making it a dud
     
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  3. Mendel Leisk

    Mendel Leisk Senior Member

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    I was going to say check for parasitic draw, but reading through, you have, albeit in a somewhat novel way. I ran wires out under the hatch, closed it, and checked there. But sitting IN the car, yeah that would work.

    If this is happening regularly, it might be the explanation. 10~20 milliamps is a very small draw, but it can eventually do a battery in.
     
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    168 hours/week * 0.02A quiescent current = 3.36Ah/week

    Capacity of new fully charged battery: 40 Ah

    It’s not recommended to take out more than 50% of the rated capacity if you care about long battery service life.
     
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  5. sam spade 2

    sam spade 2 Senior Member

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    Two things:
    The new battery MUST be fully charged before being put into service......in the car or out.
    If this is an AGM battery, one deep discharge like that might not shorten it's useful life much.
    OK....3......
    Your battery charger might have gone bad.
    I don't think I remember EVER seeing one that would automatically sense a 6 versus a 12 volt battery.
     
  6. bisco

    bisco cookie crumbler

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    i just put in a new trustart 12volt purchased from a toyota dealer. two things come to mind:

    1) it was 9 months old

    2) it was only 11 volts

    i charged it up, and it is holding at 12.9 volts after 24 hours of being off.

    6 volts is way low after only sitting for a week. i would start again freshly charged, and monitor it at the jump point under the hood
     
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  7. jzchen

    jzchen Newbie!

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    Schumacher units sense 12 V vs 6 V. If a 12 V has gone so bad, it will charge it as a 6 V, leaving you with a bad situation...
     
  8. sam spade 2

    sam spade 2 Senior Member

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    I've had 3 different Schumacher units and NONE of them claimed to be able to do that.
    They all had switches.
    I am still using one of them.
     
  9. TMR-JWAP

    TMR-JWAP Senior Member

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    Well, here we go again....this is mine...take a look at the lower right corner....and I can back up what was mentioned on post 7, as this one has done it also.

    IMG_3932.JPG IMG_3933.JPG
     
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  10. sam spade 2

    sam spade 2 Senior Member

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    Well I wouldn't trust ANY charger that claims to be able to do that......reliably.
    As the evidence provided here would tend to indicate......it is NOT reliable.

    P.S. that charger looks like it has some age on it.
    Do they still sell them like that ?
    I suspect not, and with good reason.
     
  11. jzchen

    jzchen Newbie!

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    That’s actually a newer version than what I started with, which were rectangular boxes in their earlier form. These were available at local Walmarts @ $20, and worked for the most part. Once in a rare while I would find a dead battery, even while connected to one of these. (I have several chargers connected at the same time). I would change them with a higher model. Most recently I purchased a NOCO Genius G7200.

    EDIT- No, I do not see them at Walmart anymore. This seems to be their 3A EverStart replacement:

    EverStart 3A Smart Battery Charger & Maintainer - Walmart.com

    Replacement Parts Landing Page | Page 2 | Schumacher Electric

    As one can see from the Schumacher site link above, there are still quite a few models that note “Fully Automatic 6V/12V”. I found the NOCO model because my most recent battery purchase was an LiFePO4 12 V battery.
     
    #11 jzchen, Jul 27, 2019
    Last edited: Jul 27, 2019
  12. TMR-JWAP

    TMR-JWAP Senior Member

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  13. sam spade 2

    sam spade 2 Senior Member

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    Newer is not always better.
    That is WAY overkill for a simple automatic battery tender.

    But then so are a lot of the gadgets that are present in recent cars too.

    Sometimes I think it is almost impossible to drive these days and NOT be distracted.
     
  14. DriverX5

    DriverX5 Junior Member

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    Just to add some more info prompted from your great replies so far:

    Yes the battery charger is definitely a 6v/12v automatic sensing. Made by Battery Tender. It was one of the cheapest/only options they had at Pep Boys a while back. Wish I still had my CTEK but I don't. I was only using on the failed batteries in the faint hope I could resurrect them from the dead to help troubleshoot some more, I realistically new I had no chance. Anyways that's besides the point.

    I have some confidence that nothing was left on. The couple of light switches are always on the off position, not even the door position, and everyone walks by this car on their way in so someone would have noticed during the week the "new" battery died. The "new" battery had been on the shelf since Feb, and silly me didn't think to check it's voltage when I took it home. This 2nd "new" battery had a Feb 2019 sticker on it as well, so we will see how it goes. As per your suggestion, I am leaving it on the battery tender for a while to get it's initial charge properly after 5 months of just sitting I suppose.

    I'm not intentionally trying to leave the car alone for weeks at a time, but it seems like it should be able to be left alone with no problem? The original battery lasted 12 years and was left alone for many an extended period - it was only my foolishness listening to the radio with the car off that doomed it in the end. I don't think a week at 0.02A should kill a new battery within a month...

    I guess I can't rule out a parasitic draw that is occurring at some point in time other than when I am measuring it... such as in the middle of the night or something - has anyone heard or know of any system on the Prius that kicks in long after closing and locking the car? I only checked for parasitic draw for about 10 minutes after locking myself inside, although I repeated the test more than once.

    Another note of weirdness that just happened was the old dead dash display. Got through that one by unplugging/plugging the white connector on the battery, and understand this could be due to bad combination meter - but could this possibly related to killing my "new" battery? I wouldn't think the combination meter would be trying to draw any amps while the car is locked and sitting silently in the driveway but who knows.

    Thanks for all the excellent replies and discussion.
     
  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    One example of a system that "kicks in" is the fuel system vapor control system which will test the integrity of the fuel tank ~5 hours after the car is made IG-OFF.

    I would say that there are three possibilities to consider:

    1. The new 12V battery was near depletion upon installation. You can rule this out in the future by fully-charging the battery now.
    2. A relay was stuck closed, allowing greater than normal parasitic current draw. This relay was working properly when you did your measurements. This will not be easy to find.
    3. Despite your best efforts, an interior cabin light was left on or a door/hatch was not fully closed, allowing current draw substantially above the 0.02A level for an extended period.

    The bad combination meter would not likely cause the excessive current draw. It receives power via two fuses: 10A GAUGE and 15A DOME. 15A DOME has power at all times; however I would expect a CM component failure which resulted in excessive current draw would not be an intermittent fault.
     
  16. sam spade 2

    sam spade 2 Senior Member

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    Yes it should be OK up to 30 days .......IF and only if it was fully charged when parked.
    Since you have no way to know that, a tender is the best idea.
    You got really lucky with that 12 year battery life. In most situations, 6 years is good.
    Are you the original owner ? Any chance that you forgot the battery had been changed about 6 years ago ?? ;)

    THEN.....just because it is new does not mean that it is "good".
    You NEED a voltmeter to check the charging voltage and to see what happens to the resting voltage of the battery too.
     
  17. DriverX5

    DriverX5 Junior Member

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    Happened to notice my brake actuator buzzes a lot more frequently than I remember it doing nowadays. So I searched the forum and found this:

    Brake actuator "warranty extension" from Toyota | PriusChat

    In Post #3, he says his brake actuator was triggering quite often, even when the car was off. Do you guys think this might be my problem? I haven't noticing it triggering with the car off, besides when you first open the door after unlocking, but then again I don't sit there and listen to the car while it's off for extended periods. I will try to do next time I wash it, unless anyone has any other ingenious ideas to monitor what goes on with the car while it is off and parked in the driveway?

    Many thanks!
     
  18. bisco

    bisco cookie crumbler

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    i guess it's possible. leave a phone out there and listen...
     
  19. jzchen

    jzchen Newbie!

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    Brake actuator, or brake accumulator maybe? That one activates when one opens the driver door (car off).

    moto g(7) power ?
     
  20. DriverX5

    DriverX5 Junior Member

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    Yeah that one. Seems to be buzzing everytime I push the brake pedal nowadays.