Off the grid batteries and cold weather

wacnstacwacnstac Registered Users Posts: 5
I am planning an off the grid installation with solar panels, batteries, and an invertor with generator pass through for backup. The issue that I have yet to solve is this.... The installation is more than 1/3 mile from any existing grid power and is only frequented once a month in the winter. I can't think of any way to protect the batteries from the temperatures which are often below zero in the winter. The batteries will be left to charge in the intermitant winter sun which while scarce would be enough to maintain a charge but certainly not enough to heat the battery house.
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Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Off the grid batteries and cold weather

    they would be fine if fully charged and given a float charge to maintain them from solar in the grid's absence. it is when they are in various degrees of discharge that the electrolyte has a higher water content and could then possibly freeze depending on the soc and the temperature. many people put their batteries in an enclosed battery box and you could place a bit of foam insulation around the batteries, but give them room to breath and that goes especially on the top if you elect to place some there. it is best if the insulation has foil facing to strip it off where there is even a remote possibility of a short.
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Off the grid batteries and cold weather

    A fully charged battery will not freeze, at least not in the low temperatures most of us experience. A fully charged battery should be good to something like minus 75 F. Of course at that temperature its effective capacity is reduced.

    If you leave the batteries fully watered and fully charged with a recent EQ charge they should come through the winter alright with the charge controller charging as it can. Our RV batteries (4 6 volt GC2) made it thru several winters with a cheapy controller and a cheapy PV panel supplying the juice. EQ in spring or whenever you can get back up there.

    This coming winter the newly built cabin with it's own PV off grid system will be doing the same thing. This has better equipment Outback FM60 controller) than the RV. The only draw on the batteries will be the few watts that the Outback Fm60 uses while sleeping. It has been suggested to me that I set the absorb and float voltages down to the lower end of the acceptable range to minimize battery water loss. I may also adjust the absorb "end amps" setting so the controller will go into float when the absorb amps falls to 1 to 2% of the battery bank capacity, rather than let the entire absorb time run out first.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • wacnstacwacnstac Registered Users Posts: 5
    Re: Off the grid batteries and cold weather

    Thanks for the info. I guess I won't worry about the AGM that I have currently at this remote location that is connected to a 50W panel with a decent charge controller. Mountain Don, I have almost no idea what you are talking about but someday it will mean something to me once I get into this stuff.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Off the grid batteries and cold weather

    Don't worry about it.

    It drops to -40 here in winter, and at 52 Lat the sun makes very short appearances by Dec 21. Left on their own all winter (Nov through May) my FLAs have always survived. They are inside and surrounded by 3" of foam insulation. Between this and the available charge current they don't freeze.

    If you're really worried about it, get AGM or Gel batteries. Although you can expect to pay a lot more per Amp/hr for that extra measure of freeze protection.
  • wacnstacwacnstac Registered Users Posts: 5
    Re: Off the grid batteries and cold weather

    Thanks guys. An equalize charge is not likely in my future. The only charger that I have that will do that needs to run off a generator and the equalize cycle takes over 24 hours.
  • mike95490mike95490 Solar Expert Posts: 8,500 ✭✭✭✭✭
    Re: Off the grid batteries and cold weather
    wacnstac wrote: »
    Thanks for the info. I guess I won't worry about the AGM that I have currently at this remote location that is connected to a 50W panel with a decent charge controller.

    AGM should NOT be equalized, and certainly not for 24 hours.
    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 ,

  • icarusicarus Solar Expert Posts: 5,398 ✭✭✭✭
    Re: Off the grid batteries and cold weather

    A fully charged battery won't freeze till way below -40f Even at 50% charge they won't freeze until well below 0f. We have a number of sets that sit on Pv and have for more than ten years, with temps to -50f.

    Some where in one of these links is a chart of State of charge VS freezing temps.

    http://www.batteryfaq.org/
    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

    T
  • westbranchwestbranch Solar Expert Posts: 5,176 ✭✭✭✭
    Re: Off the grid batteries and cold weather

    If you tell us the specifics of the battery and panels (make, ratings etc) we can better review your system for you... you can add it to your sig line if you like, saves a lot of repetition sometimes.

    Don't worry about the AGMs they will come through the winter fine... as said before just have them fully charged and at least a 3% amp charge rate relative to battery capacity.

    cheers
    Eric
     
    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
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Off the grid batteries and cold weather

    The freezing point depends on state of charge. The more discharged the less sulfuric acid in solution and more water therefore a higher freezing point.

    At 40% state of charge the specific gravity is 1.148 (21% acid) and electrolyte will freeze at -16 deg F. At 100% state of charge the specific gravity is 1.278 (37% acid) and electrolyte freezing point is -92 degs F.

    This assumes no stratification which is when acid concentration is higher at bottom of battery and lower at top due to long term float charge with no significant discharging or charging to keep mixture uniform.

    AGM's are still lead-acid batteries, although probably not so much vunerable to stratification of electrolyte as flooded cells.
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Off the grid batteries and cold weather

    Seems like a good thread to throw this out...

    Soon I will have winterize my RV. :cry:

    My original plan was to connect to shore power in the garage and let the ProSine 2.0 keep the batteries floated. I have four Deka 8AGC2's connected series/parallel for 12V. The dealer that I bought them from said I should just make sure that they are fully charged, disconnect them and then "put them to bed" for the winter. I don't think he understands the accuracy of the ProSine's charging capabilities, but given the apparent "hardiness" of the AGM and it's sensitivity to overcharging, I think I am coming around to his point of view.

    Opinions?

    Craig
  • BB.BB. Super Moderators, Administrators Posts: 29,832 admin
    Re: Off the grid batteries and cold weather

    Check the voltage on the battery while "floating"... Ideally, should be just a bit above the "resting" voltage of the battery.

    Personally, I put a cheap lamp timer on the charger and set it to charge for 1 hour a day (more or less-your choice). Same as letting it charge for 1 day a month.

    Had very good luck with this on car batteries for vehiciles that sit for long periods of time and have relatively large standby loads (Lojack, GPS, OnStar, computers, etc.).

    Only issue--sometimes the trunk gets left cracked open a bit and the trunk light kills the battery (1 amp charger is not on long enough keep up with the lamp).

    Before doing that--either the batteries boiled dry or went dead in a month or so (again, standby loads in this case--I have other, older cars without the fancy stuff and they sit for long periods just fine).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Off the grid batteries and cold weather

    If I had my RV sitting at home where I could watch things I's charge 'em up, pull the disconnect and take a reading every month and then recharge if and when necessary.

    I guess there's nothing wrong with setting a timer instead.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Off the grid batteries and cold weather

    These are AGM batteries. If they are fully charged when they are put to bed they should not freeze and should lose very little charge. They will be "sleeping" for about five months. I will be able to give them a "bump" over Christmas/New Years, if necessary.
  • westbranchwestbranch Solar Expert Posts: 5,176 ✭✭✭✭
    Re: Off the grid batteries and cold weather

    being a cautious pessimist, I would go the timer route and check them around Christmas just to be sure everything is working the way you want it to...

    Eric
     
    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
  • mike95490mike95490 Solar Expert Posts: 8,500 ✭✭✭✭✭
    Re: Off the grid batteries and cold weather

    I thought one brand of AGM's were able to withstand a freeze, or is that all brands of AGM ?
    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 ,

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Off the grid batteries and cold weather
    mike90045 wrote: »
    I thought one brand of AGM's were able to withstand a freeze, or is that all brands of AGM ?

    You're right: it's practically impossible to freeze an AGM under normal conditions (Baffin Bay not withstanding :p ) and their self-discharge rate is much lower than that of an FLA. Best kind of batteries to have in a cold climate.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Off the grid batteries and cold weather

    any claims or not, i would treat any battery as if they could freeze and crack and take the precautions of keeping it charged and some insulation.
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Off the grid batteries and cold weather

    Insulation is only good if there is a heat source to keep one side of the insulation warmer than the other. Even the best insulated box with no heat input will have the interior eventually be the same or close to the exterior temperature. Insulation can slow down the change, that's all.

    How much charge would it take to warm the acid to where it could make a difference?
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Off the grid batteries and cold weather

    The charger is a Prosine 2.0 3-stage with manual equalize.

    I can't see how it could possibly harm the batteries to be connected to that charger 24/7 unless the charger itself failed and overcharged the batteries.

    Aside from charger failure, would it not be better to have the batteries kept at full charge during a 5 month winter layover than to have them self-discharge at all?

    Put another way: Isn't 0 discharge better then >0?
  • icarusicarus Solar Expert Posts: 5,398 ✭✭✭✭
    Re: Off the grid batteries and cold weather
    Insulation is only good if there is a heat source to keep one side of the insulation warmer than the other. Even the best insulated box with no heat input will have the interior eventually be the same or close to the exterior temperature. Insulation can slow down the change, that's all.

    How much charge would it take to warm the acid to where it could make a difference?

    While that is technically correct, that is anything will eventually take on the ambient temp. batteries will produce a fair bit of heat while charging and discharging. My old set sat in an unheated shed year round. The ambient would average ~-30f over the bulk of the winter. The batteries (4 l16's) were on ~125 watts of panel. With small occasional loads, and charging, the insulated battery box would often times be way above zero F.

    I personally wouldn't worry about solar batteries until -40 for an extended time. Even then putting them in an insulated box wouldn't hurt.

    Tony
  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Off the grid batteries and cold weather
    icarus wrote: »
    batteries will produce a fair bit of heat while charging and discharging.

    My point was that batteries just sitting there over winter will not have a lot of discharging or charging going on, and therefore not making much heat.


    I have a friend who insulated his water pipes believing it would prevent then from freezing. Naturally with no heat in the building for 4 months it did not save the pipes.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Off the grid batteries and cold weather
    Insulation is only good if there is a heat source to keep one side of the insulation warmer than the other. Even the best insulated box with no heat input will have the interior eventually be the same or close to the exterior temperature. Insulation can slow down the change, that's all.

    How much charge would it take to warm the acid to where it could make a difference?

    a small float charge from solar or any other source will create a small amount of heat that under adverse conditions and being left alone long term to be worthy of some insulation.
  • TronTron Registered Users Posts: 20
    Re: Off the grid batteries and cold weather

    Could connect a cheap 1W or so solar trickle charger directly to the battery as insurance in case the charger should fail. I swear by those things for cars that sit for prolonged periods of time.
  • _OS__OS_ Solar Expert Posts: 207 ✭✭✭
    Re: Off the grid batteries and cold weather

    I have been running a system with AGM batteries, two 80W panels and 1200VA inverter for more than two years now without any problems. In the winter the temperature is often below -20 C (-4 F).
  • bobdogbobdog Solar Expert Posts: 191 ✭✭
    Re: Off the grid batteries and cold weather

    We have a cabin that is closed up 4-5 months a year. There are other cabins as well. Everyone has solar of some sort or another. I have yet to hear of anyone's batteries freezing during the winter if they are kept connected to adequate panels/charge controllers.

    Some, if not many, have no battery box let alone insulation around the batteries. I have one year in without either. Temps get well below zero in the winter and mine didn't freeze last winter.

    I am concerned about equalizing during this time though and so turn it off. I'm more afraid of losing fluid (aka water) than of freezing.

    However, this year I plan to build a box AND insulate it. As they say, a ounce of prevention beats a pound of cure....or something like that! :blush:
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Off the grid batteries and cold weather

    bobdog,
    can't you shut down your auto eq when it's unattended? the eq isn't needed, but the float charge is needed to maintain them while unattended.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,869 ✭✭✭✭✭
    Re: Off the grid batteries and cold weather
    bobdog wrote: »

    Some, if not many, have no battery box let alone insulation around the batteries. I have one year in without either. Temps get well below zero in the winter and mine didn't freeze last winter.

    I am concerned about equalizing during this time though and so turn it off. I'm more afraid of losing fluid (aka water) than of freezing.


    When unattended set your bulk absorb to the float setting and obviously do not do an EQ. Top the water before you leave. DC diconnect the inverter/charger

    What I have not heard in this discussion (or I missed it...) is the real need for insulation below 45F or so is for people who are using batteries during the winter. There is a definate drop of capacity and it has to be accounted for in the design process if batteries are getting cold. The capacity comes back when temperatures rise. I try to get clients who are in the design phase to stay away from remote sheds and keep the batteries near the living space so it can be easily conditioned.
    I did not say in the living space as John Wiles did at one time......
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • bryanlbryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: Off the grid batteries and cold weather

    One of the big issues with batteries just sitting is stratification and is its impact on battery life. You want to 'exercise' the battery a bit as well as keep a top charge on it during storage for maximum life.

    A float or trickle charger will keep the battery charged which will help keep a top charge and avoid freezing but it doesn't help with the sulfation problem from stratification and lack of exercise.

    The Battery Minder (tm) features a desulfation technique to add to the trickle charge and it seems to work well for battery storage. This is based on a Home Power magazine article published about ten years ago. (I have heard they make a charge controller with this technique built in now, too)

    For RV's, a converter such as the Progressive Dynamics intellipower with chargewizard works well as it uses a periodic voltage bump to keep batteries healthy. This technique may not be appropriate for AGM's.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Off the grid batteries and cold weather

    Stratification is also more of a problem with "tall" batteries like L16's than "short" ones like T105's.
    In practical application it is not a major concern. Some charge controllers can be programmed to perform an EQ once a month. If the batteries are charged and filled when left and the Voltage/time set points are correct this will see them through the winter. If there's no automatic EQ, it is a good idea to perform one once the batteries are "put back into service" in Spring.

    It is not an issue with AGM's.

    In the end, you can drive yourself mad trying to "tweek" performance to squeeze every last minute of potential usable life out of your batteries. If you're concerned about longevity, my advice is to buy good ones in the first place and make sure your charging parameters are set at the manufacturer's recommendations.

    And remember: some of us have got 10 years usable service out of batteries that should have only lasted 5, and some of us have had batteries fail in 1 year that should have lasted 5. You do the best you can and it's still a crap shoot. :D
  • System2System2 Posts: 6,290 admin
    Re: Off the grid batteries and cold weather

    ok. i am new to many things. one is this whole forum and the other is off grid living. thanks for any help you can give me.

    so i'm working on an offgrid houseboat and my newest hurdle is designing my battery box. i have two concerns, one is venting and the other is freezing. its going to be cold on that boat quite a bit. especially at times when i'm away. if i build an insulated box can i assume that the heat the batteries will generate in the day through charging will keep them from freezing at night? does anyone operature there batteries under below freezing conditions? if so, how?

    then there is the problem of tryign to figure out how to insulate my box while also keep it vented. my understanding is that the batteries will be offgassing hyrdogen?

    does anyone have design suggestions for me?

    oh. i have four crown 225ah batteries. thank you thank you thanks!!
    adam
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