Overvoltage Warning
 

Started the plane today and got an overvoltage warning on my GRT Mini. Voltage was reading 14.4 on the gage, which is a bit higher than normal. Is this an indication of a failing voltage regulator (I have a Nippondenso alternator with built in regulator)? I can probably increase the warning parameters on the GRT, but am I risking damage to any of my avionics or electrical? What?s a ?safe? upper limit?
Terry, CFI
RV9A N323TP

The sky is falling, the sky is falling!
 

14.4 volts is within the normal charging range for GM Chrysler and Nippon Denso alternators. You need to raise the alarm level on your mini. Ford voltage Regulators normal is 13.8 to 15 volts. If you're using an Odyssey battery or some other form of sealed battery you actually would like the charging voltage to be about half a volt higher than what is normally used for flooded acid batteries. I would suggest you raise the alarm level to about 15.5 volts. I know the alarm level on B&C's voltage Regulators is actually 16.0 volts.

Charlie

Thanks Charlie!
 

I?ll reset tomorrow. I?m doing my condition inspection and probably let the battery run down too much while testing things. Never saw the warning before on my EFIS, but it was the end of a long day and brain and body were running on reserve. Appreciate the details in your response.
Terry

B&C's over voltage warning kit has their gizmo preset for 15.2Vdc. The failure I saw was an occasional flicker of the over-volts warning lamp, gradually progressing nearly full time. Buss voltage was 15.4 volts at that point. Replaced the external rectifier/regulator on my 2-wire system and all is good since.

Hum ... Odyssey battery manual state : Monitor the batteries terminal voltage with the charger operating to assure 15.0V is not exceeded at any time....

Source : https://www.odysseybattery.com/docum..._Procedure.pdf

16 volts is the normal upper limit. Most modern avionics can support up to 32 volts, and temporary excursions above that for very short periods of time (<1 sec).

Overvoltage conditions need to be rectified within milliseconds, so it's best, IMO, to have some sort of OV protection system that can shut down the alternator much faster than a human. Your OV alarm is usually a popped alternator field breaker.

Low voltage is a different beast, and is not nearly as time-critical.

I know automotive voltage regulators regulate the voltage based on outside temperature.

The colder it is, the higher the charge voltage can be for a lead-acid battery.

So the regulators will raise the voltage when it's cold.


Airplane regulators probably do the same thing.

Not sure what era you're talking about here but I don't see this on any of my Denso, Hitachi or Bosch equipped alternators circa 1990-2010.

Please clarify
 

I'm a little confused here. What do you mean by B&C over-voltage kit? My previous comments were based on B&Cs LR3C voltage regulator technical manual revision C Circa 2016 09 16.

https://bandc.com/wp-content/uploads...anual_revC.pdf

On page six it states: " the integrated over-voltage protection function is set at a non-adjustable 16.0 volts plus or minus 0.2 volts on the LR 3 C - 14." On the top of this same page it also states that this voltage voltage regulator comes preset to a charging limit of 14.4 volts. However the user can adjust the maximum charging voltage as he or she sees fit.
Perhaps we are referring to two different B&C products??? Since you mentioned rectifier regulator I suspect that you are dealing with either a model SD - 8 or model SD - 20 Dynamo style backup alternator system.

Charlie

Not quite
 

Ed, that's not quite right. Automotive internally regulated alternators can only measure their own temperature. They can lower or raise the charging voltage based on that temperature. The assumption is that the battery is also located under the hood and therefore will be at a similar temperature.
Some modern automotive and marine charging systems have the voltage regulator built into the PCM ( powertrain control module AKA engine computer). These systems can monitor the temperature of the alternator and also of the battery. They are able to adjust the charging voltage to compensate for either of these items starting to overheat. As you also mentioned they can raise the charging voltage when the temperatures are low. This is being discussed on another thread here. I believe the title of the thread is PlanePower versus B & C.

http://www.vansairforce.com/communit...d.php?t=176462

Charlie