Hi there,
So have a look at the “Grove Expansion” 
search results of course a Demo I did using it, adding the external Flash chip to the bottom of it Code is included to test it and compiler output versions for the C3 and nRF52840 and 3D printed also some different size cases and holders for it. It is very versatile and easy to use. Displays, One wire Temp probes, switches , bussers, lots of Grove accessories. Allows quick assembly of shakedown prototypes and proof of concepts in both software and Hardware. 
The battery management works well and would be even better if they updated it and added a PMIC ic. and that way true battery management can be off MCU board. It’s seeed achilles heal on a lot of there products that purport to be suitable for battery power or wearables. Only the WIO terminal includes a battery management chip you can query a whole host of parameters and even the Battery voltage , Imagine that! SOC,(state of charge) and hrs used for very accurate battery life and management data.
interrupts for certain parameter levels and conditions, I2C configuration makes it a snap…
That is my take on it
HTH
GL 
PJ