Low Voltage Alert Threshold

[Rob58]

Many systems provide an annunciator for low and high voltage conditions. Trying to determine if there is an accepted threshold for alerting to a low voltage condition? Is there any generally accepted setpoint for sending off an alert? I'm dealing with at 14V system but also interested in the low voltage value for a 28V system. Appreciate all comments!

 

[455 Bravo Uniform]

Opinion: 12.6 to 12.7 is a healthy battery at rest. If my charging voltage gets below this number, I am running off the battery and need to be warned. POH would supersede here.

 

[MooneyDriver78]

Opinion: 12.6 to 12.7 is a healthy battery at rest. If my charging voltage gets below this number, I am running off the battery and need to be warned. POH would supersede here.

Charging voltage should never get below 13.0, I would set it so that you would get an alert as soon as possible. If below 12.6 it has been on battery for a while.

 

[AV8R_87]

Alert for anything below 13V and above 15V.
Double that for a 28V system.

 

[Bell206]

Trying to determine if there is an accepted threshold for alerting to a low voltage condition? Is there any generally accepted setpoint for sending off an alert?

It usually depends on the purpose of the alert and which part of the system you are looking at.
If addressing a battery (12v/24v) low voltage I've seen triggers at the 11-12v/18-20v range. For example, on the newer 24v Cessnas with a Garmin 1000 I believe the trigger voltage for switchover to the emergency battery is at 20v on the main battery bus. But I don't have a book available to be sure.
But when addressing the system side (14v/28v) it varies as those values can be dynamic due to system charging, load levels, etc. But a common trigger point I've seen is +/- 2v for a 14v system voltage and +/- 4v on a 28v system. For example, on some helicopter 28v systems the over-voltage relay would trip at 32v.
If looking for a specific application I might be able to find a real reference with some details?

 

[kontiki]

It usually depends on the purpose of the alert and which part of the system you are looking at.

I agree. As far over voltage goes I'd maybe look at battery data and charging requirements.