[Creeker]

I've read a fully charged lead acid battery has a freezing point at around -80F to -90F. Even at only 40% SOC its freezing point is around -15F to -20F.

This is the reason I unplug ours and top charge them several times during the winter. I have zero worries of freezing. However, they will slowly discharge over winter and do need top charged to keep the lead sulfate from hardening and crystalizing on the plates.

This lead sulfate is a normal process during every discharge cycle. It is easily converted back to lead and acid if the battery is recharged soon after use. The longer it stays without being recharged the less it converts back and shortens battery life.

Charge those lead acid batteries a few times through the winter!