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Physics questions: Battery freezing

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Posted by I can't do that Dave on December 2, 2006, 12:44 am
 


Hi people,

I have a friend who lives off the grid (solar + wind) and is concerned
with the battery charge getting low and the fluid freezing.

My view was that if it is cold enough for the electrolyte to freeze, it
will do it fully-charged or damn near flat at about the same temp.

Can someone set me straight with some Physics here please?

Thanks in advance.

Dave


Posted by on December 2, 2006, 8:57 am
 


On 1 Dec 2006 16:44:54 -0800, "I can't do that Dave"


From the Trojan Battery FAQ:

"Can a battery freeze?
The only way that a battery can freeze is if it is left in a state of
partial or complete discharged. As the state of charge in a battery
decreases, the electrolyte becomes more like water and the freezing
temperature increases. The freezing temperature of the electrolyte in
a fully charged battery is -92.0F. At a 40% state of charge,
electrolyte will freeze if the temperature reaches approximately
16.0F. "

Posted by Windsun on December 2, 2006, 2:55 pm
 

Wrong - a fully charged battery is good to at least 40 below zero, usually
more (depending on the specific gravity of the electrolyte in that battery).

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Posted by DJ on December 2, 2006, 6:09 pm
 


I can't do that Dave wrote:

Does the battery on his car freeze? Same thing. IF the battery charge
gets low, ie, around LVD territory, yes, they can freeze.


They won't freeze. I have dozens of clients who keep their battery
banks outside (cottagers and seasonal homes) and only the ones who
accidentally forgot to, for instance, turn off their inverters at the
end of the season, lose batteries.

DJ


Posted by Bruce in Alaska on December 2, 2006, 7:59 pm
 



It isn't Physics, but Chemistry, and a fully charged battery will not
freeze, even down in the -60F range, where as a fully discharged battery
can Freeze and Crack in the +10F range.  This is for flooded PB/Acid
Wetcells. AGM's and GellCells can freeze and die at much higher temps.

Bruce in alaska     one who has much practical experience in this area...
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