Help understanding Beetle CM-32U4

I am looking at using the Beetle CM-32U4 for an upcoming project. Can you help me understand the battery function of the controller? It is a 5v system but only supports a 3.7v lithium battery. If I was going to use it as a battery powered device and have it chargable, how does it operate at 3.7v? I will be using the PWM to control a few other devices as well. 

Thanks,