Mike was having trouble with his computer. He was getting very
discouraged. It would dump the B computer fuel map.

Is a voltage drop causing computer problem?
This is more likely to occur if your batteries are in
the back of the airplane. I would run heavy
wires for the starting and alternator  functions
and a separate smaller wire directly from the battery for the main bus.
The reason is the battery acts as a giant capacitor so starting
and alternator glitches are less noticed on the main buss.

Here is a sketch of his wiring design that Mike drew and that I
have edited a bit.

The other possibility is the computer is not sensing a power down
situation and not cleaning up what it is doing in software. A way of doing
that is add a small 5 volt rechargeable battery that keeps
power on the computer long enough to clean itself up.

This can mostly be done in software if one analog to digital converter
is dedicated to monitoring the raw 12 volt supply. If the voltage
drops below say 9 volts the computer starts cleaning up the software
for shut down. Kind of like old Windows where you had to tell it to
shut down and Windows would clean it self up before actually shutting
down.

The 5 volt regulator feeding the computer usually has a very large
capacitor that can keep 5 volt power on the computer long
enough to clean it self up. This capacitor can serve as
the small five volt battery.

Paul Lamar