D180 shuts off when I crank engine

[jaroberts2pe]

I have yet to start engine, but when I crank engine, the D180 shuts off, then reboots about 5 seconds later.  I do not have the internal optional battery installed.  What's happening and can I fix it?

Battery voltage when I begin cranking shows 12.6V. Why would bus voltage drop to <9V and cause D180 to shut down? When this happens I will not be able to monitor oil prressure on start-up. Must I have back-up battery?

 

[PhantomPholly]

I have yet to start engine, but when I crank engine, the D180 shuts off, then reboots about 5 seconds later.  I do not have the internal optional battery installed.  What's happening and can I fix it?

Easy way to find out. Without turning on the master, press and hold the left button on the Dynon. If the unit does not come on, either you don't have the internal battery or it is dead.

 

[dynonsupport]

Most likely this is because the voltage at the D180 is falling too low during cranking. The starter draws hundreds of amps and causes the battery voltage to drop. Depending on your wiring method, the voltage at the D180 may be even lower than the battery.

The D180 turns off at about 8V if I remember correctly.

As you know, an internal battery will prevent this, but it may just be that your aircraft battery is low. Make sure it's fully charged when trying this test.

 

[SammyQ2]

I am having the exact same thing happen, on my D180. I have a brand new Odessy battery and the engine is turning over, quite merrily, but the D180 goes blank.

I don't have the internal battery.

 

[jaroberts2pe]

Battery voltage when I begin cranking shows 12.6V. Why would bus voltage drop to <9V and cause D180 to shut down? When this happens I will not be able to monitor oil pressure on start-up. Must I have back-up battery to avoid this problem?

 

[dynonsupport]

The bus voltage drops because the starter draws 100+ amps from the battery. Batteries have an internal resistance and follow ohm's law. You can see this even without putting a whole starter load on the battery. Measure the voltage at the battery with no load. Then turn on all your avionics, lights, pitot heat, etc. Now check the voltage. It's lower because of all the current flowing.

Additionally, depending on how you're wired, it may be that the starter and the bus are sharing some current paths, so any resistance in the cables is causing a voltage drop to your bus as well.

The internal battery is not the only way to solve this, but it probably is the simplest. That being said, most customers do not have this issue so it is solvable with wiring or battery changes.

 

[PhantomPholly]

If you use your D180 as primary engine monitoring, the internal battery should really not be considered "optional."

I get the "Low voltage" alert each and every time I start, but because of the battery have full monitoring of the engine throughout.