Lora-E5 mini board power behavior

Hi, I couldn’t find any detailed (electrical) specs for the board. Currently I am evaluating the Lora E5 for a project and need to know more about the behavior of the board. so I am testing more or less with trial and error.
I was measuring the 5V and 3.3V pins when powering via USB and alternatively via 3.7V rechargeable battery. The wiki specifies possible input Voltage between 3.7V and 5V. When I supply 5V the 5Vpin also measures 5V. When using a battery with less than 5V as input, then the 5V pin drops to roughly 1V. the The 3.3V pin measures 3.3V in both cases.
While this behavior might be obvious due to the lack of voltage regulation on the board, I think it might be helpful to find it documented in the wiki and data sheets…