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landyacht318's avatar
landyacht318
Explorer
Feb 14, 2015

Frigid weather floating with non temp compensated charger

I got a friend up in Michigan who put a voltmeter on his 1.5 year old 'maintenance free' Starting battery and found it 11.95v, and claims there is Zero parasitic draw.

He put his automatic charger on it, and said it went into float quickly. I instructed him, online, to bleed off the surface charge and restart the charger, but later remembered that both battery and charger are outside.

Life got in the way several days passed, and tonight he says it has been floating for days, at 13.2v, In Michigan, in this recent cold snap. 2.5 hours after removing charger voltage fell to 12.9v.

I am not sure the average temps there, but I doubt it has gone above freezing in quite a while.

Using USBattery's temperature compensation and a 13.2v float at 80F, float voltage at 10 degrees F, would be 14.37v. The charger apparently does not even have ambient air temp compensation and has been holding 13.2V.

So what is happening to the battery floating at 13.2f at say 10 degrees F. Is it still self discharging? Is it being discharged by the charger?

I've told him he should take the battery and charger somewhere warmer, let it warm up and restart the charger, but I am curious what happens in these extreme cold sub freezing temps when the 'smart' charger still thinks it is 77F outside.

9 Replies

  • landyacht318's avatar
    landyacht318
    Explorer
    Feb 16, 2015
    JRN, I've not been following it closely. I'm in San Diego and not dealing with Senior 'Polar Vortex'

    My Michigan friend apparently has no intention of getting past the 'maintenance free' portion of the flooded casing. Can't say I blame him. I'd not want to be outside working in 0F and 30MPH winds, even long enough to unhook the battery to bring it inside and have a go.

    I've just been trying to make him realize how incredibly stupid his bells and whistle 'smart' charger actually is, especially at 0f, and its attached marketing mumbo jumbo, is worthless.

    He does not want to believe this.
    Green lights are just so soothing.
  • westend's avatar
    westend
    Explorer
    Feb 16, 2015
    Pretty good article on battery charging and temp compensation here, at Solar Pro. They give formulation for temperature/voltage settings.
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Feb 16, 2015
    LY,

    Not sure if you're following my 'Very Low OCV' thread, but I'm dealing with the same issues. Perhaps that thread will help shed some light?
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Feb 15, 2015
    I was charging at 15.6 -16v, and my resting ocv's were a little lower than usual, so I thought maybe the voltage was a little high, even for the cold temps. (I find in the warm weather, too high a voltage results in lower ocv's). So I thought maybe once the batteries were warmed up from charging, the voltage didn't need to be as high. Well the result was the ocv plummeted. So higher voltages are definitely needed.

    This past Thursday, at 12F, ocv was 12.57v. After warming the cabinet under the bank with a microfurnace, and warming the battery cabinet with a hair blower to 44F, ocv rose to 12.63v.

    I have tried to find information about the effect of cold on resting voltages, but cannot find anything. There is, of course, no shortage of info about temp compensating charge voltages and SG readings, and how cold slows self discharge, but nothing about resting ocv. But it does appear warming the bank will help raise resting voltage. And of course it will help with battery acceptance.

    If your buddy's charger is preset too low, he will definitely have to bring the battery in from the cold... especially this weekend.
  • landyacht318's avatar
    landyacht318
    Explorer
    Feb 15, 2015
    A hydrometer was my first suggestion to my friend, but it is a 'maintenance free' battery and he is not so eager to figure out how to access the cells, and was asking my opinion as to the battery condition given just the voltages and charger behavior.

    Having no experience with battery charging at Sub zero temperatures, I thought I'd ask here.
  • mchero's avatar
    mchero
    Explorer
    Feb 15, 2015
    I have a 93 Pace Arrow that has wintered MAY times here in the N.E. w/o any charger. I get both house & chassis batteries juced up & then hit the disconnect switch. NEVER (Knock on wood) had a battery discharge then freeze.

    RM
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Feb 15, 2015
    In breve. Hydrometer. Anything else is as accurate as diagnostics made by a 10-year old girl. OK it's now the end of my last 500 peso cel time purchase. 4 pesos left...
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Feb 15, 2015
    Hey LY,

    I'm about 6 hrs west of Michigan, and yes it's been quite nippley here... well below freezing for the most part. A few snowy days at or just above freezing, followed by another deep freeze. Normal temps are supposed to be around 25F at night, and around freezing for a high, but it's been much colder... as low as 15 below zero F. This weekend we're having another cold one. (Now that I think about it, that may be what's causing my resting ocv to be lower than last winter? The other day I warmed up my bank and Vbatt actually rose, just from being ~ 30F warmer.)

    I'm wondering if he has the portable charger at too high an amp setting, and it's forcing up the voltage too fast, and thus kicking it into float? (It doesn't take much to drive up the voltage on a starter battery at a high amp rate). Just a guess.
  • westend's avatar
    westend
    Explorer
    Feb 15, 2015
    What happens is that the battery is never fully charged (assuming the battery gets some use). If it;s just a Winter float process, the 13.2V is prolonging the life of the battery but not to it's ultimate health. IOW, 13,2X at 10f is better than nothing but not as good as it can be.

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