I'd set it a bit higher than the highest voltage your battery puts out.
When it dips below that trigger, then you can be assured your alternator
is no longer carrying the electrical load of the aircraft and the
battery is discharging.

Dave

markp wrote:
Hi All,

I'm looking for recommendations for a low battery warning voltage level. I
was going to use 12.8V - is this liable to be triggered by noise/dips in the
bus voltage? My guess is when heaters or motors kick in there could be a
momentary drop due to high current that could trigger my low voltage
indicator. Also it it worth putting a long time constant filter on this?

Thanks!

Mark.