Deciding what level to set battery indicator

[SNEAKxxATTACK]

I am progressing well in my GCP, most things are mounted, and now I have finally decided what batteries will fit. I can get 8 3.7V Li ion cylindrical cells, with the configuration in my head, it ends up 5200mah with 14.8V

Now to my question, how do you decide what voltage to set your battery indicator to?
I have a feeling that you need to test how long the battery lasts with everything working before things start shutting off separately (is that how it works? Things shut off separately from insufficient voltage)

Then you would need to measure the voltage at the time you want remaining, before the moment things start to shutoff separately.

Please help clarify this for me
Thanks

Edit:

Yes, set the low battery indicator light to somewhere around 0.2v higher than the cut-off point where things start to fail, especially if it's the console that goes off first. If like the PSone screen the screen goes off first, then a low battery indicator is of no point as the screen starts to get wavy first, so that's your indication.