We are going through a record broken coldest winter here, my 2018 NAPA premium performance battery still holding okay, labelled (640a) CCA still can be read around 540 (aprox 85%) in garage parking (-10c), to prevent it from dying due to extreme coldness, I had to open hood and plug in charger every night in past whole week. I'm thinking to install a permanent battery charging connection on my bumper, similar to a block heater, no need to open the hood every day to recharge.