question:
If I get this 1s-6s voltmeter display, can it be wired in parallel with the charger? or does the charging circuit have to be disconnected/switched-off to use this display?
example: incorporating OP's idea, can this 1s-6s voltmeter (link $2.88) be soldered/connected permanently to this microUSB charger (link $3.40) or something like this Universal Charger (link $2) while charging?
I suppose if it is soldered-on, it will always show ~4.2V during charging, and actual battery voltage only when you disconnect the power? this way, one could avoid adding a 3-position on/off swich (link $1) to the voltmeter display. Similar to the setup of Ledoman (link), except his setup is only a display, not a charger. Cottonpicker on CPF's ForSale item has a switch, though I don't know if it is to toggle between Voltmeter Display VS Charging.
related ebay pictures:
