Ok what is happening is that the battery voltage on the ePower is drooping or lowering , this is normal . batteries under load will reduce there voltage as the load increases . So really the eP is giving you around 3.2 volts NOT 3.7 volts !
A regulator controls this and keeps the voltage constant , that is why there is a difference .
Thanks Mike. I can tell there is a difference, just didn't know why. Just sharing my experience. Sometimes I am hesitant to post in forums because I don't know all of the technical issues. But I appreciate you explaining it in easy-to-understand language.