off grid batteries

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Eros

Member
Location
United States
I have been quoting several off grid solar solutions to that have hunting cabins in cold climates. is there a economical solution on how to keep the batteries in a controlled and warmer climate which will allow for more efficient charging and longevity ?
thanks
 
I have been quoting several off grid solar solutions to that have hunting cabins in cold climates. is there a economical solution on how to keep the batteries in a controlled and warmer climate which will allow for more efficient charging and longevity ?
thanks

Actually FLA batteries last longer when they are colder. Obviously they will be ruined if they freeze but if its,an occasional use cabin, they will be floating most of the time anyway so they will never freeze. Now the capacity does go down with temperature so that may be a consideration. Some people make an insulated battery box - I'm not sure how much that keeps the temp above ambient (I don't use one so I have no data, maybe try one of the RE forums).
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
With sufficient insulation it might be possible to let the waste heat from the float charging cycle keep the batteries above freezing. On the other hand, during the warmer months when the cabin sees greater use (I'm assuming; dangerous, I know) you could cook the batteries during the normal discharge/charge cycles associated with utility use in the cabin, unless one is very careful to remove the insulation.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
With sufficient insulation it might be possible to let the waste heat from the float charging cycle keep the batteries above freezing. On the other hand, during the warmer months when the cabin sees greater use (I'm assuming; dangerous, I know) you could cook the batteries during the normal discharge/charge cycles associated with utility use in the cabin, unless one is very careful to remove the insulation.
One could install a thermostatically controlled vent fan.
 

mgookin

Senior Member
Location
Fort Myers, FL
There has to be somebody who has dealt with this. I know we have one guy >70deg lat right now but I don't know if he ever did solar. Come to think of it, that's not a good place for solar! (unless you have REALLY big batteries).

I did some searching and came up blank. Aren't there any industry organizations? Or maybe manufacturers who will consult?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The electrolyte in a fully charged lead acid battery will have a freezing point between -60 and -90F, and this is not affected by wind chill.
The key point for keeping the battery happy is to use a temperature compensated charged with a remote temperature probe, since the voltage necessary for full charge increases as the battery gets colder.
If you need to actually use the battery with reasonable capacity, then you would need to heat it from the inside cabin environment.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Are we talking lead-acid batteries here? Lately I've seen lithium installed. It's probably of importance to the topic to confirm what chemistry we're talking about.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Are we talking lead-acid batteries here? Lately I've seen lithium installed. It's probably of importance to the topic to confirm what chemistry we're talking about.
Good point. Lithium (with possible variation based on the exact chemistry) can be used, although with much reduced performance, down to -22F.
Not sure what the minimum safe storage temperature is.
 

iwire

Moderator
Staff member
Location
Massachusetts
Are we talking lead-acid batteries here? Lately I've seen lithium installed. It's probably of importance to the topic to confirm what chemistry we're talking about.

After watching so many lithium batteries burn up on youtube I doubt I would sleep well with a large connected stack of them in the house. :eek:hmy:
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Are you saying there is not a real issue with lithim batteries burning up?

The FAA won't let hover boards on planes due to the fires that are happening.
There is more than just one lithium chemistry used in batteries. Most are very stable.
 
I have lived off grid for 12 years and I do not have automatic heat. I also travel for work for 2,3,4 weeks at a time so my place freezes right up shortly after I leave during the winter - the cat doesn't keep the wood stove going ;). I don't see cold batteries as being an issue for systems where: 1) the batteries are in a space that is heated while occupied, 2) there are no (or insignificant) loads running while the place is not occupied. So in this situation the batteries will not freeze due to their state of charge and although they will have reduced capacity, when the place is occupied and heated the batteries will warm up and they are coming off a full charge anyway. Now if you have some load that will be running while not occupied then there is a chance of an extended period of the array being covered with snow perhaps you could get into trouble, but even that is unlikely as you will most likely have the panels mounted at the ideal winter angle for off grid which is over 60 degrees off horizontal here in central NY, and snow wont stay on them for long.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
In some cases, such as a wide expanse of clean white snow in front of the panels, a straight vertical orientation may actually collect more light in winter and not accumulate snow at all.
 

iwire

Moderator
Staff member
Location
Massachusetts
There is more than just one lithium chemistry used in batteries. Most are very stable.

Are you disputing the fact that many lithium batteries from phones to power tools have been burning up?

It's not just about self ignition it's also about how they respond to damage.

I am not saying I won't use them, all I am saying is I doubt I would put a large stack of them inside a building I sleep in.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Are you disputing the fact that many lithium batteries from phones to power tools have been burning up?
No. I am saying that there are different lithium chemistries that are used for batteries and some are more likely to cause heat incidents than others, and that the ones that have done so get lots of attention, and that many folks think that all lithium batteries are the same.
 
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