On Feb 6, 12:25*pm, brianDG303 wrote:
On Feb 6, 8:38*am, Dave Nadler wrote:

PS: This configuration is not an ideal diode;
does not prevent crossfeed as an ideal would...

Question, if you want to keep it pretty simple and just have two
batteries, for example a big 12 volt 15AH like a 12150 and a smaller
back-up like a 4AH Li-Ion. *Then this is wired to an A B switch and
you only use the Li-Ion for emergencies. *OK, finally the question.
When you switch from A to B doesn't the computer restart? *I have
heard of a capacitor you can connect somehow to provide enough voltage
to keep everything from dropping off like, but now we aren't keeping
it simple anymore.

Cheers,
Brian

Back in 2007 I was preparing for a Convention speach, and I asked the
current flight recorder manufacturers how their devices handle a power
outage during the dead period when you switch between batteries (both
on nonwithstanding). Look at
http://aviation.derosaweb.net/presen...iring_2007.pdf
page 26 for the details. This has grown a bit long in the tooth as
quite a few new recorders have come on the market. The bottom line,
most will continue to create a single log file even with a power hit.
That being said, you will loose GPS until the system comes back on
line.

As to adding a capacitor. Yes, adding something called a "super cap"
can store enough energy (like a small battery) to handle the time
between Battery A and Battery B. Some devices even have them built in
(Borgelt?).

I have never had an issue with running my batteries in parallel 100%
of the time (with switches of course) but maybe I have just been lucky
over several hundred flights. But I am growing to like the general
thread of this discusion - running battery A until it gets low, then
switch in battery B, then turn off battery A - all without loosing
power to anything. See...even I can learn a new trick!