Some time ago I bought a Victron BMV-712 Smart battery Monitor.
It is possible to see the various measurements
by pressing the ‘+’ or ‘-‘ buttons and scrolling through the display or linking, via bluetooth, the monitor to a smart phone and looking at the figures on screen.
Useful, but you do need to have the phone handy.
Recently I came across a couple of old phones (put in the back of a drawer when I upgraded) and it occurred to me that I could set one of them up as a permanent display. The only possible problem would be how to power the phone, fortunately the Solar Power MPPT controller came with a USB port.