Warming Batteries

TombslTombsl Registered Users Posts: 13 ✭✭
Over the winter would it be a good idea to leave a low voltage light on in the battery compartment to help keep it warm ?


  • mvasmvas Registered Users Posts: 383 ✭✭✭
    Are you getting the power for the light, from the battery ?
    Is the battery fully charged now ?
    Will the battery be on a FLOAT Voltage charger ?
    Is the battery unattended during the winter ?
  • mike95490mike95490 Solar Expert Posts: 9,274 ✭✭✭✭✭
    Lithium battery or Lead acid battery ?     
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • mvasmvas Registered Users Posts: 383 ✭✭✭
    A fully charged battery should be OK down to -70 F or even lower.
    The battery manufacturer should provide minimum temperature vs SOC specs
    Your outdoor temp is -40 F / C ?
    I assume you have Solar Panels to maintain a 100% State of Charge via Float Charge ...
    So technically, Fully Charged the battery should be OK.

    If you have excess power from the Solar Panels then I would use a "12v Heating Pad & Thermostat" vs a light bulb.
    Insulate (but do not seal) the battery box.
    Use an adjustable bulb-type freezer thermostat to control a raw heating pad, something like this one ...
    Do not buy a heating pad that comes with a controller that has the 30 minute auto-shutoff safety feature.
    Power the Heating Pad from the Solar Panels only, not from the battery.
    Put the bulb/probe of the thermostat inside the battery box, keep the switching unit outside.
    The lead is massive and will hold heat during the night.

    Maybe, you could keep the internal temperature of the battery near 0° C in the box when -40° C outside?
  • TombslTombsl Registered Users Posts: 13 ✭✭
    Thanks so much.  Great ideas!
  • mvasmvas Registered Users Posts: 383 ✭✭✭
    Only, a Fully Charged battery is safe down to -56° C.
    A fully discharged battery will freeze at about 0° C.
    So, keeping the battery at 100% SOC is very important.
    That is my reasoning for not using any power from the battery power for heating.

  • TombslTombsl Registered Users Posts: 13 ✭✭
    Yeah.  I was wondering why you suggested powering the pad from the batteries, but then realized you had already built in the possibility that the pad would deplete the batteries and they would freeze.  So  I guess I'll need another controller to regulate the voltage from the panels to the pad ?  Thanks again!
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