Hi there and welcome to the SHOW… 
Ah’s the SEEED Studio’s
The code name “XIAO” here represents its half feature “Tiny”, and the other half will be “Puissant”.
"Elaborate Power Design: Provide ultra-low power consumption as 5 μA in deep sleep mode while supporting lithium battery charge management"
"Seeed Studio XIAO nRF52840 Sense is carrying Bluetooth 5.0 wireless capability and is able to operate with low power consumption."
"strong software compatibilities, which supports Arduino, Micropython, and CircuitPython. Except for the software"
YMMV...
IMHO, They need a DISCLAIMER though! (none of the battery crap works out of the box)
I suggest you look at this post HERE, Msfujino He has the battery reading on the Expansion board mod on Lock. 
SEEED engineering a.k.a. (marketing) on the other hand DOES NOT!!! 
HTH
GL :-p