Is it worth it to heat agm battery box

just starting
just starting Registered Users Posts: 235 ✭✭✭
in Off Grid Solar & Battery Systems #1
Would it be worth putting a 24 volt computer fan to push heat from my house to an outside box my battery's are in the - 3-7 c range would keeping the battery's around 50 f e worth the amps lost to the cold
200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #2
    At those temperatures you are probably only getting 70% of your battery's nominal capacity, so I could understand why you would want to warn them up a bit. Getting the temperature up to about at least 10-15°C would make a big difference. I'm not sure a computer fan would manage that unless the air ducting and box were heavily insulated. If you can accomplish the required insulation then it's just a question of waiting the required time for the huge thermal mass of the batteries to slowly absorb the heat - possibly a couple of days...

    It could be worth it if you do it right;)
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #3
    The batt box is 2x4 construction with r13 and 2" blue foam board its only 3' from the house So I have some PVC the problem is that my woodburner is about 6'total from the box So I t will get heat at night
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #4
    what are the lowest winter temps you get?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #5
    -25f for a few days in a row weeksto months of -10f
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #6
    I'm on the back side of pikes peak in colorado if you know where that is.
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #7
    well from me that would be the sunny south side... o:)
    My choice would be more insulation and if the power (W) used to run the fan is low enough over a 24 hr period in you opinion, go for it and have the warm air enter at the bottom, warm air rises, and exit out the top , use a smaller pipe for exit, and make a U shape down and up to stop siphoning of the warm air out and cold back in.

    Batteries also warm a little when being charged, more if they are not in top shape.

    You could also dig a pit for them next year and the ground will ameliorate the temps summer and winter...  insulated as well of course.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #8
    West branch how many w PV do you have total
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #9
    1680 W so far and 2 x that to come if needed....
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #10
    I have 1500 panel ready with breakers for another cc and array I have an 894 ah agm bank kind of similar
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #11
    1500 pv and 250 e panel
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #12

    Might be worth it if you don't over do it.

    Lots of insulation around the box, maybe use 12 volt reptile warmer pads on timers and temperature switches to keep the pads off if above a certain temperature and only run them for a few hours aday.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #13
    I was just going to get a 24 volt temperature control and put the sensor on the battery post and stop at 50f
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • animatt
    animatt Solar Expert Posts: 295 ✭✭✭
    #14
    Are you running out of power? Or for what reason  do you want to heat the batteries.   As long as they are above freezing and you are not running out of electricity I see no point in heating them.

    I am in what most would consider a tropical climate.  I would love to keep , my  batteries at such low temps. 
    Battery life is extended  the cooler the battery.

    Matthew
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #15
    I'm afraid of voltage drop because of temperature a few times under load my voltage was at 24.7 at -6c if I can bring up the temp ill get 30 percent of bank power back
    And more opportunity loads during sunlight +
    less time to charge
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #16
    When you look at using a 1/2 amp computer fan for 24 hours so 12 amps and a 894 ah bank 30 percent is a lot of lost power
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #17
    If you are planning to just vent the return air outside you will be adding a large heat loss to your dwelling space. But, especially if using FLA you have some issues to deal with when returning air to the inside.
    A fluid loop with a heat exchanger on each end and simple convection for flow would be more thermodynamically efficient and not risk getting acid vapors back into the house.
    SMA SB 3000, old BP panels.
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #18
    I have a fisher mama bear in a 600 sf dwelling I have more heat than needed. I just plan on venting to the outside maybe some one way valves with ping pong balls to keep flow one way and to stop flow without a fan
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • animatt
    animatt Solar Expert Posts: 295 ✭✭✭
    edited December 2015 #19
    It is lost storage capacity.  If you are not using the capacity makes no difference.  But if you. need the capacity definitely something to investigate.   Would seem really easy to test to see if it is worth it.

    With 30% more capacity  would take longer to charge (assuming you are going to be using that extra juice). And opportunity loads can be somewhat independent of battery size (with in reason)
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #20
    I've been hitting float everyday even on cloudy days most usage was 3.5 kw but want a chest freezer and washer I have a converted chest freezer to fridge and TV cell phones and x box for the kids five cfl and 2 gcb on 12 v for water pumping but have been charging them with 110 charger
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #21
    Thank you about explanation of storage I miss understood.
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #22
    Does that mean I have about 3 kw storage for two days at 50 dod
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #23
    just starting said:
    Does that mean I have about 3 kw storage for two days at 50 dod
    My understanding of the effects of cold on the batteries is that the amount of energy in them is the same, you just cannot get it out as well.
    In which case you might try only warming the batteries if you see that you are going to be challenging your autonomy limit.
    Cold batteries are going to last significantly longer before they degrade than warm ones too.
    SMA SB 3000, old BP panels.
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    #24
    Do any of you know how to get a steady 24 volt 2 amp supply from 24 volt battery bank.During charge the volts go up the 30 sometimes don't want to burn up the fan or thermostat
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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  • Hill_Country
    Hill_Country Solar Expert Posts: 96 ✭✭
    #25
    Just Starting....

    We have a 48 volt DC system, but needed steady 24 volt DC for some of our home-circuits to run two DC fridge/freezers, 3 DC ceiling fans, and some DC LED lights at 24volts.  We ended up using a Solar Converters, Inc. DC-DC Converter that stepped down the voltage from 48v (nominal) DC to 24 v DC.  It keeps a steady 24v DC (actually we have it set to 28 v DC).  In your case, since you're going anywhere from 24 volts to 30 volts DC input (during charging, equalize, etc.) to a steady 24v DC output, you'd need something that takes a variable DC voltage in and outputs a steady DC voltage at an acceptable current (2 amps), which shouldn't be hard to find.  I did a quick search and found this for a variable 24 v DC input and a steady 24v DC output:  www.axiomatic.com/TDAX080200.pdf

    Please note, I am NOT endorsing this product, nor do I have any experience with the product...personally, I would recommend you contact NAWS (the host of this site) and see what they have equipment-wise...they were very helpful for me when I was faced with the DC-DC conversion I was facing.  Hope this helps!
    100% Off-grid with: 8 Solarworld 275 Watt Panels, 8 Concorde SunXtender 405aH 6v AGM Batteries, MS-4448PAE 48v Inverter, MidNite Solar Classic 200 Charge Controller, 10,000 gallon rainwater collection system, etc.
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  • arby
    arby Solar Expert Posts: 108 ✭✭
    #26
    I think when you use the bank, it warms itself up.
     Once upon a time,in extreme cold, people would turn on their car's headlights for a minute or two  before they tried starting the engine in their car.

    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
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  • softdown
    softdown Solar Expert Posts: 3,896 ✭✭✭✭
    #27
    Wonder what happened to this concept? So many of the old do-it-yourself type ideas were quite sound.


    arby said:
    I think when you use the bank, it warms itself up.
     Once upon a time,in extreme cold, people would turn on their car's headlights for a minute or two  before they tried starting the engine in their car.


    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #28
    arby said:
    I think when you use the bank, it warms itself up.
     Once upon a time,in extreme cold, people would turn on their car's headlights for a minute or two  before they tried starting the engine in their car.
    softdown said:
    Wonder what happened to this concept? So many of the old do-it-yourself type ideas were quite sound.

    The battery's ability to heat itself by discharge (or to be heated by charging) is a function of its internal resistance.  AGM batteries have very low internal resistance and therefore do not heat up very much when in use.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #29
    One person here posted (long ago, as I remember) would use a genset (winter cabin) to get the place warmed and lights on. Had a battery heater in an insulated battery box. After 8 hours, cabin and batteries where warm and the batteries kept warm enoigh from daily cycling.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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