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Cold Weather Cabin

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DarenG20

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Joined
Sep 21, 2019
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Hello everyone! I live in the Upper Peninsula of Michigan where the winter temperatures can drop to -20 degrees F. I’ve been asked to install a battery bank where a generator is used as the charger at a hunting cabin in the woods. The cabin is used mostly in the summer and fall for deer season, but it is still used in the winters every other weekend for rabbit hunting. I have the system planned out, and contacted local suppliers about what they think should be done to preserve the batteries and render them useful through the winters. They suggested lead acid batteries, fully charging them then disconnecting all loads before leaving camp in the winter. This seems like a good suggestion, but what would I do if I wanted to use the batteries for the couple weekends I am there in the winter? I’d assume they’d be pretty cold.

Thanks in advance.
Daren
 
Up here in Nova Scotia at our forestry camps we use lead acid cause they are cheap.

The guys are in for a week normally and the camps are heated while they are there. Same as when they are in there hunting. They take a battery in and take it with them. These camps are all DC lighting. Super basic setups.

However they take them with them when they are done. They freeze!
 
Mtt04, thanks for the reply! That seems like the most logical explanation and I was really hoping it wasn’t the only thing to do. The system will have a bank of four batteries to reduce generator run time and save fuel. If I choose lead acid, that would be kind of a pain to haul in and out with how heavy they can be, especially on a snowmobile in the winter.
 
Lead acid capacity drops significantly in cold temps. And internal resistance increases. So be sure to build a MUCH larger than necessary battery bank if you are using lead acid.
 
Some put them in an insulated pit to take advantage ground temperature. That may not be possible. Some independent vertical panels to resist snow can be used to heat the battery compartment.
 
I'm contemplating a similar conundrum myself. I'm toying with the idea of leaving the batteries in place in the winter, and when they're not in use, using a well insulated water tank as a thermal dump load when the batteries are full, and hoping that the thermal energy from the tank, positioned below the battery bank will be enough to keep them from freezing. It's still just a thought I'm playing with though.
 
I took everyone’s replies into consideration when deciding what to do. I have the setup finished, not very pretty but functional. We haven’t had severe cold yet, so it’ll be interesting to see how well the plywood and foam enclosure (located inside the camp) holds heat . It is also slightly ventilated on the sides in the rare case the batteries off gas. Four 100Ah AGM sealed batteries, and a 1000w inverter/charger combo unit from Renogy to utilize the generator for charging. Romex runs to a manual transfer switch near the breaker panel to isolate the generator and inverter circuits. Alhough the combo unit has a 20A automatic transfer switch, I wanted to be extra safe for a bunch of card playing, late night stumbling, hunters. Solar panels (and/or wind turbine as tree coverage is dense surrounding the cabin) and a charge controller may be added next summer when more funds are available.

Results have been achieving a 23hr (3-4 nights) run time from 13v full to 12.3v 50% on the battery bank from running all LED lights and phone chargers.

Feel free to critique my work, it was my first system install and would love to improve for the next one.
36FE96CD-8AC2-498E-B2A8-6C7F43FE8229.jpeg7B218541-56B3-4404-9F44-3F20D937E556.jpeg7B218541-56B3-4404-9F44-3F20D937E556.jpeg
 
Observation more than a critique... you could have shortened the wires significantly by turning the inverter over. It doesn't have to be mounted label side up.

And a thought for warming... what if you were to make a solar water heater on the roof which, with a small circulator, warmed a tank of water. Once the temp near the batteries drops to some pre-determined level, circulate the warm water to a small radiator, like an automotive heater core, around the batteries.
 
Rider said:
Observation more than a critique... you could have shortened the wires significantly by turning the inverter over. It doesn't have to be mounted label side up.

And a thought for warming... what if you were to make a solar water heater on the roof which, with a small circulator, warmed a tank of water. Once the temp near the batteries drops to some pre-determined level, circulate the warm water to a small radiator, like an automotive heater core, around the batteries.
Click to expand...

I appreciate the response! I agree with the orientation of the inverter shortening wire lengths, although it’d drive me more crazy staring at an upside down label than longer and less tidy wiring...
Believe me, I contemplated it...

As far as warming goes, that is definitely something that can be done, but for now I am hoping the thermal characteristics of the foam will suffice to keep things simple. The charger has a thermal couple input (white wire) that measures the battery temperature and will adjust charging voltage/current accordingly. As far as batteries completely freezing, I am also hoping the ambient temperature in the enclosure stays just above 32 F which would be plenty warm for fully charged batteries after reading the article that “Monty” shared above.
 
DarenG20 said:
I took everyone’s replies into consideration when deciding what to do. I have the setup finished, not very pretty but functional. We haven’t had severe cold yet, so it’ll be interesting to see how well the plywood and foam enclosure (located inside the camp) holds heat . It is also slightly ventilated on the sides in the rare case the batteries off gas. Four 100Ah AGM sealed batteries, and a 1000w inverter/charger combo unit from Renogy to utilize the generator for charging. Romex runs to a manual transfer switch near the breaker panel to isolate the generator and inverter circuits. Alhough the combo unit has a 20A automatic transfer switch, I wanted to be extra safe for a bunch of card playing, late night stumbling, hunters. Solar panels (and/or wind turbine as tree coverage is dense surrounding the cabin) and a charge controller may be added next summer when more funds are available.

Results have been achieving a 23hr (3-4 nights) run time from 13v full to 12.3v 50% on the battery bank from running all LED lights and phone chargers.

Feel free to critique my work, it was my first system install and would love to improve for the next one.
View attachment 1343View attachment 1344View attachment 1344
Click to expand...
Nice and neat, well laid out, I like it. You should install a fuse on the positive lead at the battery, yes, fuse blocks, terminal crimps and fuses for that gauge cable are available typically at electricial supply houses. Also, if you had a way to relocate the batteries to a cellar hole that's 6' deep and has no wind movement, your batteries would remain above freezing and work better but you could even upgrade to the Lithium Ion Phosphate batteries which blow the doors off of lead acid based batteries. Happy Hunting!
 
Very interesting thread... similar situation for me in New Brunswick, Canada. I have 4 12V Lead Acid AGM batteries. I don't have solar panels yet so i was hoping to charge my batteries with my generator. I want to hardwire an inverter to my breaker panel. Would it be possible ( or necessary) to generate a small amount of heat from a DC light bulb within an insulated box as described above? Would that consume too much energy out of the battery bank that it would defeat the purpose because i'd have to spend my time running the generator while i'm there just to charge the battery from heating the box...
 
CoachMcG said:
Would it be possible ( or necessary) to generate a small amount of heat from a DC light bulb within an insulated box as described above? Would that consume too much energy out of the battery bank that it would defeat the purpose because i'd have to spend my time running the generator while i'm there just to charge the battery from heating the box...
Click to expand...

Update on my build:
The system has been working alright, although not living up to my expectations. As the temperatures have dropped and we are in the middle of a snow storm predicting 28” of snowfall, I have noticed the 12v sealed AGM battery capacity has dropped substantially and the amount of time to recharge increased. We have been running the generator way more than we have hoped. Even in this enclosure, the batteries get pretty cold and I think that is the cause.

I have considered buying a heating pad, either 120v AC or 12V DC to warm the batteries while the generator is running and the batteries are charging, and disconnecting the pad when running off batteries alone. That may be a simple solution to the problem, which may help you too.
 
DarenG20 said:
Update on my build:
The system has been working alright, although not living up to my expectations. As the temperatures have dropped and we are in the middle of a snow storm predicting 28” of snowfall, I have noticed the 12v sealed AGM battery capacity has dropped substantially and the amount of time to recharge increased. We have been running the generator way more than we have hoped. Even in this enclosure, the batteries get pretty cold and I think that is the cause.

I have considered buying a heating pad, either 120v AC or 12V DC to warm the batteries while the generator is running and the batteries are charging, and disconnecting the pad when running off batteries alone. That may be a simple solution to the problem, which may help you too.
Click to expand...

Something to consider... my concern is more for when i'm away and the camp is left unheated for a week or two. I can drive to my camp year round so the easy fix would be to bring them home with me and charge from home. Again, if i understand the chart that was posted, i should have nothing to worry about next winter if the solar panels keep the battery bank fully charged. I'll probably keep a temperature log from inside the camp this winter. I kept an eye on it last year but never recorded it. I don't think it dropped any lower than -20° C (-4°F)
 
Thanks for posting the update and results. I am going to be building a similar heating box for this winter. I am also considering a heating pad.
 
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