Winter solar battery charging when you can't add water?

"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 -92F. At a 40% state of charge, electrolyte will freeze if the temperature reaches approximately 16F." I'd take them with me.

Source of information "Trojan Battery Company"
Trojan Battery Company Website