External Alternator installation

Look on page 113...  Or,

Check the current installation manual Ed.3 Rev 0, section 24-00-00, Page 9.

"A capacitor of at least 22,000 μF/25 V is necessary... "

Bill,

Thank you once again.  I saw that and believe it refers to the internal charging system rectifier-regulator.  I am not an electrical engineer and don't know how to size the capacitor, but wouldn't the external alternator which produces a higher amperage maybe need a different size capacitor to do that same job?  It makes sense to me that for a bigger job you might want to use a bigger tool. But then what do I know, I'm just an old retired Air Force guy having fun I might add.     

I was told by Rotax dealer in Canada that the requirement for a capacitor with the external alternator might be a misprint, and, in any event, it is not normally installed.

Ken,

Thanks for that information.  I agree the external alternator with a built-in regulator might not need a capacitor to absorb energy if it were shut off while the engine was still running.  (Rotax's reasoning for why the capacitor is there.)  And that would be an accepted installation in an automobile where independent switching of the device is not available.  But of course, aircraft have to be different so they can charge more for the parts. <joke> 

The Cap is there only for insurance, it is not needed at all... Until it is!!!

If the Alternator could never be disconnected from the battery, it would not be needed.

The presence of an Alternator Switch and a Fuse/Breaker is what makes it necessary.

The actual size is not at all critical, but they needed to specify something and there was no need to create a new part when they already had one that was Close Enough.

Be sure to wire it BEFORE any Switches or Fuses/Breakers.