Apple Watch Series 4 Battery Life

Hi I have recently purchased the Apple Watch Series 4. The problem I am having is when I dont have my iphone with me the phone charge drops dramatically even with me not using it. It drops between 20 and 30% in around 45 mins. I am guessing this is not normal. It means I am basically not even getting a full day out of it. I bought the cellular version and pay the extra to my phone provider to be able to use it this way however not able too as the battery level drops too low. Can anyone offer any suggestions. Thanks in advance