Cold Weather Battery Use and Care

Cold can be good and bad for a battery.  It’s good to store batteries in a cool environment as the cold slows down chemical degradation of your battery.  But the cold also robs the battery of working capacity.  Don’t count on a cold battery to deliver the same amount of energy as a warm one.

Standard recharge times assume the cells inside of your battery are at 25C so, a colder battery takes longer to fully recharge, meaning not only will a colder battery deliver less energy but it will also take longer to recharge. 

Finally, there is a risk of irreversible physical damage from a frozen battery as a deeply discharged battery is more susceptible to freezing.

Approximate State of Charge (SOC)	Freeze Point	SG (temp corrected to 25C)
	FLA & AGM	Measurable in FLA only
100%	-57C	1.265
80%	-52C	1.250
75%	-39C	1.225
50%	-27C	1.200
25%	-15C	1.150
~5%	-7C	1.100
0%	0C	1.000

To offset cold weather effects and to ensure a full charge, a higher charge voltage is required.

Never assume your default battery charger settings are adequate!  A good charge controller senses temperature and will automatically compensate the charge settings for the cold.  The best charge controllers include a remote battery temperature sensor that is affixed directly to the battery (or even in the battery) for the most accurate readings.  But they’ll still take longer to recharge than a warm battery so expect less performance from your battery in winter than the rest of the year. 

Be sure to confirm your batteries see a full recharge at least once every week or two.  If an Equalize charge is required, try to get the battery warmed up before charging.