Newbie with AGM batteries in Cold Temperatures.

[Jdub]

Hi.

I'm new to solar. Here is some background information. Due to Covid I have not been able to travel to set up my system at our cottage. I've done tons of research and have decided on what equipment I can use with my budget at our off grid cottage. We go up every weekend all year round, so we can check on the system once every a week or two weeks max. We are in southern central Canada where winter's get down to -25°C/-13°F for at least 2 months in the winter. We are off grid, use a wood stove for heat and a generator for electricity but would like to off set the cost of fuel with free energy that solar can easily supply most or needs for the weekend. I would like to continue charging my system in the winter weeks while we are unable to provide wood burning heat. The only option would be by solar. The winter months are too cold to facilitate charging and I would like to know if anyone has ever made insulated self temperature regulating heated battery box with 12v/24v low watt heaters/blankets for AGM batteries. Looking for advice. I have 12v temperature monitors that can cut power and some low watt heaters with fans. Not sure if I'll go this route. I also want to keep water/liquid storage from freezing during the week. I was thinking of using a similar system to heat or maybe combining the two. I don't think I should store the batteries inside near the water but it would be convenient. I only need to keep batteries and water/liquids just above freezing. I am also concerned about venting of AGM batteries and probably better to keep them separately in an outside container. I can set up my AGM deepcycle batteries to provide 12v 500AH and am trying to limit my heater to under 100watts, but I have a 150 watt heater/fan as well as temperature monitor that I was going to try in a 2 inch styro insulated container. No practical tests can be done until the freezing winter months and Covid-19 restrictions end. Advice and sharing what you did in a similar situation with low temperature battery charging, keeping water from freezing over 5 days while your away would be greatly appreciated! Thank you, I believe you can view my system setup in my profile?

 

[Craig]

I think if you built an insulated box and lined it with a few layers of something like this https://www.homedepot.com/p/Thermas...-Rigid-Foam-Insulation-Board-613010/100573703.
Then added your heater on a thermostat you would be good to go. The only thing I wonder about is if the venting will let the cold air in. I think you could use very small vent holes so as to let the gasses out and not the hot air. I would build it big enough to store my water in as well. Or if you had a closet build it all in there with layers of insulation.

Just some Ideas no real experience though. This is why i Use cold weather LTO batteries

 

[Jdub]

Awesome. That's pretty much the idea I was going with. When these batteries get tired I can re-think this. Although the water will always need the heat if I can do it. Thanks for your response. I wonder if anyone else has had to do something like this?

 

[Craig]

It has been talked about and way back when someone did an experiment with an Ice Chest but I think it was a half hearted effort.

 

[Silentpower]

Hi, just an opinion on venting of sealed (vrla) batteries (after 7 years of agm experience off grid)
Any venting indicates trouble, and escaped gas represents loss of capacity. The term valve regulated is misleading inasmuch its not regulating any thing other than a last ditch safety feature to prevent the casing bulging enough to split.
The most important thing with agm is absorbtion charge length of time. Gassing will occur in individual cells if the cells are not given time to naturally balance with an absorbtion charge, given that equalising is not suitable for agm. Float current is just enough to prevent self discharge and keep voltage high enough for optimal capacity, but low enough to prevent gassing.
So a healthy system should be safe. Fla, completely different story as gassing is inherent in the design due to the equalisation charge.

 

[15Fozzie]

Renogy Canada sells a specially designed battery heater mat that has a thermostat built in.

 

[DASH]

AGM batteries do pretty well in cold weather (when compared to other batteries). Some sites suggest that they can withstand cold temperatures as low as -75 F. with a fully charged battery. Of course, You wouldn't get much performance at that temperature. Check the specs of Your battery, You may find that it's not necessary to provide auxiliary heat.

 

[Nicholas11]

for example everything suits me and I don't need to change anything

 

[HARG Hunter]

Going through a similar situation. Our off grid cabin is in Northern Wisconsin. We'll only be here every 3-4 weeks however, so the cabin stays unheated for 3-4 weeks at a time.

Are we best served disconnecting and taking the batteries home and bringing them back each time?

We have 200 watts of panels and 200ah of AGM's.

 

[Rbertalotto]

I have AGM batteries in my boat, my RV and my converted electric tractor.......They all stay outside in New England winters all year. All on Optimate or Solar chargers. I've never had an issue with my batteries. The RV batteries are 6 years old and the boat is 5 years old......All using Duracell 12V 110Ah AGM Group 31......As long as they stay charged, no need for heaters.