Is there a way to measure battery voltage while charging, or will will measure the charging voltage?
battery chargers and BMS know the voltage, but I don’t think they can help me to measure the voltage.
Of course you can measure the voltage of your battery while charging. Use a volt meter in parallel or a Watt meter in series.
What sort of charger are you using? My Lipo charger shows the voltage the battery pack is at the moment. With the balance lead connected it also shows the voltage of each cell.
It is true that in theory every measurement influences the result, but I think we can neglect this effect here.
Charger, BEC and voltmeter looks good.
One input: the VESC BEC is also the PPM input (input from the receiver) so you will have to soldier a custom wire or buy an Y-cable and cut it.
Batterie also looks good. The drawing is somewhat unusual, but it should work.
Btw. your charger needs to be able to charge 8s (33,6V end voltage).
Using the Anderson Power Poles makes them very flexible and I can easily take the whole pack apart and charge them individually.
If you are using other connectors you have to buy / make a harness or soldier.
This would be the corresponding diagram (on the back of an envelope )