Over Voltage Events

[rv6ejguy]

This summer we had a customer with a single CPI experience 3 OV events over the course of a few months.

In one instance, this took out the CPI, AP, glass panels, backup EFIS battery, defrost fans and split the case on the main battery.

This airplane had a crowbar setup on the alternator and OV protection on the VPX Pro as well.

We don't know how high and for how long this event lasted but we think it was over 60V based on what fried.

I'm interested to know what others have experienced. Did your OV kick in and save the day or did you damage any electrical components? If anyone has any data logged showing the voltages reached and duration, that would be useful too.

 

[Avanza]

From literature as much as 120 V can be the result of a load dump.
That is when the battery is beeing charged and is disconected from the
alternator. The event can take as much as 400 ms. The higher the charging
current the more severe the overvoltage.
In most cases the overvoltage protection will save the electrical system.
The use of lithium batteries with low internal resistance and internal BMS
does need considerations.
Read the battery manual and be sure to use an alternator that will work
with the battery.
A battery with low internal resistance connected to a to small alternator
may cause an overload on the alternator.

Good luck

 

[DerekS]

I had one like that

In my case it was sustained and very high. I wasn't the pilot, but was my plane. Analog airplane so no data logs.

Best guess as to what happened in my case: The ground serving both as reference to the regulator and the OV protection was weak, so the voltage at that local ground drifted up, and the alternator was ultimately asked to provide its full amps sustained. Everything that was attached to the good ground got fried.

Secondary effects of lightning can also induce significant voltages, albeit for much shorter durations. I've also lost radios to that.

Derek

 

[Steve Barnes]

OV event about 15 years ago. Took out everything on the panel that was on.

Radio, transponder electric trim, and whatever else was on at the time. FIRE and smoke in the cockpit too from the trim guage .