FLY RC Magazine - Weekly Wing Tips: PORTABLE BATTERY WARMER

I enjoy flying off snow, and I developed a way to preserve the power in my backup batteries while on the flight line in cold weather. I fill a Ziploc bag with uncooked rice, microwave it for a minute, wrap it around my batteries and put them in a room-temperature insulated cooler. Off to the flight line I go with a supply of charged batteries that will stay at peak power regardless of the cold.