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Battery question at low temps.

Discussion in 'Power Systems' started by JCruse, Dec 18, 2017.

  1. JCruse

    JCruse

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    When the outside temps drop to around freezing or below the resting voltage on my car batteries drops quite a bit from it's normal 12.8v or more, landing around 12.62 and staying there until it gets warmer. Now if I recall correctly this is normal (?) but when I went searching for a chart or something I found nothing. So if someone could school me on this I'd be much obliged. Thanks.
     
  2. george_tlc

    george_tlc SILVER Star

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  3. JCruse

    JCruse

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    I don't know about this. It says at 20 degrees subtract 0.144v. That would make my charged battery 12.65v (12.80 - .144 = 12.656) but I'm getting 12.35v after a very cold night or two. Admittedly the battery is connected but only to the HU and amp, everything else is disconnected this time of year.

    It's a sweltering 33 today so I've got it back on the charger.
     
  4. george_tlc

    george_tlc SILVER Star

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    Do not assume that 12.80V is your standing 100% fully charged battery voltage. You need to find out what the manufacturer states the 100% state of charge voltage is for the particular battery model you have at nominal 80F. This is voltage with NO load.

    cheers,
    george.
     
  5. JCruse

    JCruse

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    Lifeline says 13V for this house battery. But that's disconnected.

    I always new that batterys give less juice in the cold (duh) but I didn't know that they just didn't have anything to give. They actually lose the voltage somewhere. I charge it to 13.2 say, and that night it's down to 12.3 if it's in the 20's or teens. Where'd it go? :poop: ?
     
  6. george_tlc

    george_tlc SILVER Star

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    Battery voltage is a chemical reaction. The voltage didn't go 'anywhere', it is what the chemical reaction provides at that temperature...

    cheers,
    george.
     
  7. half k cruiser

    half k cruiser

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    Are you having a starting issue ? More so then what's to be expected given the temperature in your area ?
     
  8. JCruse

    JCruse

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    That's about as good an explanation as any on this subject, thanks.

    So what about sulfation then? Normally a 12.2V battery would be growing crystals at that level of discharge. Given a whole winter to do this I would think a lot of damage gets done this way. But I guess maybe crystals form more slowly in the frigid cold..?

    No Half-K Cruiser, no real issues with starting. Just slower cranking. My main concern is sulfation, and I'd like to know a bit more about how best to deal with this for battery longevity.
     
  9. Hiace4wd

    Hiace4wd

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    You could measure the CCA with one of those meters that a garage usually has, and then measure difference at freezing temperatures and on warmer days (when it cranks better)