For monitoring purposes I have one of the following:

https://www.aliexpress.com/store/product/DC-0-33V-3-Wire-0-36-Inch-LED-Digital-Voltmeter-Voltage-Meter-Volt-Panel-5V/2162059_32844639838.html

My yellow one starts measuring a bit above 3.2V, measures/updates its display ≈4 times per second and draws a little above 10mA if I recall correctly.

Available also in power source isolated (!) 4-wire versions:

https://www.aliexpress.com/item/DC-0-33V-4-Wires-0-36-Inch-Digital-Voltmeter-Voltage-Meter-5V-12V-24V-Volt/32843036408.html

Cool little gadgets.

:-)