There are a few things to consider when it comes to how long it takes to heat up a battery heated blanket. The size of the blanket, the wattage of the heating element, and the type of battery all play a role in how quickly the blanket will warm up.The average sized battery heated blanket is around 60201dx40201d, and typically has a 360-watt heating element. This means that it will take somewhere between 30 and 45 minutes for the blanket to reach its maximum temperature. Larger blankets or those with more powerful heating elements will heat up faster, while smaller blankets or those with weaker heating elements will take longer.The type of battery also affects how quickly the blanket will heat up. Lead acid batteries tend to be slower than lithium ion batteries, so a blanket with a lead acid battery may take an hour or more to reach its maximum temperature.