Mike Wills used the 2 motor cycle battery trick for the RV4.

The situation is you use both batteries for starting
and then, after a short while for charging purposes, you switch
one off for flying.

The other is kept in reserve in case of alternator or battery
failures. This probably puts a glitch on the main power bus when the
back up battery is switch in or out.

I will add a choke and large capacitor on the main bus to smooth
the glitch.

Paul


Just a suggestion,

Look into Aeroelectric Connection ---Robert Nucholls. Google for his
website. He is an aircraft electric Maven, involved with electronic
design for major manufacturers.

He has a constantly updated and updatable book which goes into most of
the concepts and problems of aircraft electrical systems. It includes a
multitude of schematics (circuit diagrams) ranging from the ridiculous
to the sublime, depending on what your desires are. His website also has
a plethora of references as well as blogs, bulletin boards etc.... easy
to get lost in.

A definitely recommended and perhaps required book.

Using an engine that is totally electrically dependent behooves us to be
more sophisticated in our electrical approach---- unless we have some
glider training.

Rich

Does he talk about chokes on the main avionics buss?

Two of these fit Mike's battery box. I am still not sure these
are the one's he used as the batteries where missing when I picked
up the airplane.

There are a bunch of equivalents out there yet to be researched.


Paul Lamar


Just jump on the bandwagon, I too highly recommend Bob Knuckles website and book as must haves. I have been to both the EAA and Bob's electrical seminars, both are good, but Bob's written material is MUCH more in depth. He was a electrical design engineer for the likes of Piper, Cessna, Beech, Ratheon among others (hmmm, maybe he can't hold a job ;-)). Seriously, he is very versed in "owner built and maintained aircraft".

I am using his Z-14 schematic which consist OD dual alternators and dual batteries. Both systems are used for cranking and both systems can run completely independently OR together for a nice belt/suspended system worthy of a rotary install.

Well worth your time and his book is often updated for free.and I still think is only about $40.00 plus a load of additional and supporting information on his sight. He even provides professional consultation, HOWEVER, I have yet to see a question post on his list serve that he didn't happily and authoritivly answer.

Chris Barber

That is certainly the best set up for most airplanes.

I don't have room for dual alternators. Two small batteries are the next best
thing as I have plenty of room for them. The other thing is 2 alternators would
add to the RV4 CG problem while the batteries can trim the CG. One must have an alternator (each one ) large enough and powerful enough to supply the needed current. Fuel pumps, EFI, Ignition and avionics.

Paul Lamar