Bat warmers are illegal in ASA (dont remember rule off the top of my head), FED 2-4-2-A, and NCAA 3.3.5 The use of any treatment or device that fundamentally changes the specifications of bats (for example, shaving, rolling, artificially warming, or using a bat warmer) is prohibited and renders the equipment altered and unsuitable for play.Are bat warmers legal to use in High School and NCAA in Pennsylvania ?
You are correct about the ball being colder. But a composite bat being cold has just as much to do with potential problems also. A comp bat is made to flex/compress or whatever word you wanna use. When a comp bat is very cold, the ability to flex without strain is lessened. So instead of a possible flex on a hit, the fibers may break.I want to caution you against getting a false sense of security that a bat warmer will allow your DD to use a composite bat in cold weather. The temperature of the softball, which gets harder in cold weather, is what causes problems for composite bats, NOT the temperature of the bat itself.