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Thread: charging frozen batteries

  1. #1

    Default charging frozen batteries

    I have read that lead acid batteries should never be charged when they are frozen.

    I have 4 T-605's that are stacked tight against each other and I have one inch of foam insulation around them. They are in a exterior battery bay that is not heated. I have been fine until recently it's been well below freezing for several days and will be several more before it warms up.

    Not knowing how cold they where I tried to charge them with the xantrex inverter. The charger went straight from BULK to FLOAT and skipped the ABSORB stage. I tried several times and got the same result. I shot the battery terminal with a non contact thermometer and it said 27*F. I assume the batteries wouldn't charge properly because they are frozen.

    The batteries where at 12.2V when I tried to charge them. How bad did I hurt the batteries?

    What to do from here? I was thinking about bringing the batteries in until they warm up to 40*F and trying to charge them again.

    How do you keep a exterior ventilated battery bay warm when it's this cold out?

    Did anyone else wake up to frozen pipes this morning I'm heading for Mexico next winter
    2 80w Solarex / 4 40w Arco's on a Zomeworks passive tracker / 4 Trojan T-605's wired for 420ah at 12V / Xantrex c40 / Xanterex RV 2012M / Honda powered Coleman 3500w generator

  2. #2
    Join Date
    Sep 2009
    Location
    Wilmington, Illinois
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    399

    Default Re: charging frozen batteries

    Doesn't sound good. 12.2 volts means around 20-30% charge, if that. Frozen temps kill the electrolyte when voltage is low like this. Providing the plates where not damaged too bad, an electrolyte replacement may be in order. I'm sure you'll get plenty of opinions/suggestions, but in the mean time, get them batteries to someplace warmer than freezing.

    All you can do is bring the batteries into a warmer environment (above freezing) and try to charge them. Good luck and let us know what happens.

  3. #3
    Join Date
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    SF Bay Area (California)
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    Default Re: charging frozen batteries

    Be careful when you bring them in... A frozen battery can have its case cracked and when thawed, the electrolyte will drain out.

    If the batteries were that discharged such that they can freeze at 27F--then they where near dead and my have sulfated/failed from being stored at less than ~75% State of Charge for a long time.

    A 40% State of Charge battery should freeze around -16F. Either your battery is near 0% SOC, or you have some other issue (poor electrical connections, failed cell, failed controller, or something else).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  4. #4
    Join Date
    Sep 2006
    Location
    Willits, CA
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    5,618

    Default Re: charging frozen batteries

    If the batteries are at +27F, and have any charge on them, they are likely not frozen.

    BUT you might have one cell that is weak, and one cell in a bank could be frozen. When was the last time they were charged, and last equalized ?

    http://www.windsun.com/Batteries/Battery_FAQ.htm

    Do you have a remote temperature sensor for your batteries, so the charge controller knows what the battery temp is ?

    If your batteries are in cases, you could try adding warm water to the spillage area, and see if that warms them up enough. Or get a glass thermometer, and actually dip it into a cell. Or just open a cap, and peek into the cell with a flashlight, if you see fluid, all should be fine.


    Quote Originally Posted by westcoastslider View Post
    I have read that lead acid batteries should never be charged when they are frozen.

    I have 4 T-605's that are stacked tight against each other and I have one inch of foam insulation around them. They are in a exterior battery bay that is not heated. I have been fine until recently it's been well below freezing for several days and will be several more before it warms up.

    Not knowing how cold they where I tried to charge them with the xantrex inverter. The charger went straight from BULK to FLOAT and skipped the ABSORB stage. I tried several times and got the same result. I shot the battery terminal with a non contact thermometer and it said 27*F. I assume the batteries wouldn't charge properly because they are frozen.

    The batteries where at 12.2V when I tried to charge them. How bad did I hurt the batteries?

    What to do from here? I was thinking about bringing the batteries in until they warm up to 40*F and trying to charge them again.

    How do you keep a exterior ventilated battery bay warm when it's this cold out?

    Did anyone else wake up to frozen pipes this morning I'm heading for Mexico next winter
    http://tinyurl.com/LMR-Solar
    http://tinyurl.com/LMR-BigLug
    http://tinyurl.com/LMR-NiFe

    Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
    Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

  5. #5

    Default Re: charging frozen batteries

    Batteries would have to be at zero charge - 10 volts or so - to freeze at 27 degrees. So either it got a lot colder than you think, or there is something else wrong with the batteries.
    Northern Arizona Wind & Sun Forum & Website Administrator

  6. #6
    Join Date
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    Default Re: charging frozen batteries

    If they have been on some solar charge, or if they were left fully charged, it is possible that they are fully charged already, hence going from bulk to float without absorb. If you have a battery temperature sensor, it may be telling the charger to ramp down the charge current.

    A battery with anything but pure water in it won't freeze at 27f. 50% charge won't freeze until nearly -20, fully charged won't freeze until well below -50f.

    Check each cell with a hydrometer or volt meter.

    Tony

    Ps, we routinely leave batteries over the winter @ -40 with out trouble.

    Second, don't charge a frozen battery,,, but I don't think yours are frozen.
    Please note, being a moderator does not add any weight to my opinions 300 watts Siemens/BP panels,plus a Sun 90,, making ~400. ~30 amps into Rogue MPT-3024, 450 ah of Trojan T-105, Morningstar ts300 inverter, a Tri-Metric meter.a collection of antique generators, plus 2 Honda eu-1000i's (also a BS2512 IX controller) and assorted other stuff!

  7. #7

    Default Re: charging frozen batteries

    OK sorry for the confusion. I'm really new to all this. A quick visual check showed that none of the cells where actually frozen. I didn't know electrolyte had a lower freezing point than water.

    Doesn't sound good. 12.2 volts means around 20-30% charge, if that.
    The voltage charts I have seen say 12.2v = 60% and 11.6v = 20% No charge or discharge for 6 hours.

    No battery temp sensor on the batteries.

    The batteries are drawn down to 12.4v on a daily basis and recharged by the panels. If I get no sun I'll let it go to 12.0v before starting the generator to recharge. They never sit below 12.0v. Last EQ (which was the first time ever for some two year old batteries) was two weeks ago.

    Why do you think the charger skipped the ABSORB stage? I know I didn't get a good charge on them.

    If I maintain a good charge is it safe to leave them outside? High of 18*f today and back down to 0*f tonight.
    2 80w Solarex / 4 40w Arco's on a Zomeworks passive tracker / 4 Trojan T-605's wired for 420ah at 12V / Xantrex c40 / Xanterex RV 2012M / Honda powered Coleman 3500w generator

  8. #8
    Join Date
    Sep 2006
    Location
    Willits, CA
    Posts
    5,618

    Default Re: charging frozen batteries

    Battery voltage changes as the temps change, and that can be fooling your charge controller. You NEED a remote temp sensor to properly charge your batteries.
    http://tinyurl.com/LMR-Solar
    http://tinyurl.com/LMR-BigLug
    http://tinyurl.com/LMR-NiFe

    Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
    Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

  9. #9

    Default Re: charging frozen batteries

    You can also put a load on them and see if they 'behave'. Sometimes you have to draw a battery down a bit before you can charge it up.

    Trick for automotive charging. Really dead batteries won't draw current from automatic chargers, so hook up the charger and turn the lights on so that the charger starts producing current, then turn them off. It'll drop back to zero, but then will start slowly charging up. This is because of the charger, though; not the batteries.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  10. #10
    Join Date
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    20,790

    Default Re: charging frozen batteries

    Cold batteries need a higher charging voltage (one reason a Remote Battery Temperature Senor can help in cold weather).

    Measuring battery voltage for state of charge is only accurate if the battery has sat for 3 hour or so.

    Have you done a temperature corrected specific gravity measurement of all your cells yet?

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

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