any merit in running dual battery packs ?

[Bill Glaze]

In those days a twin engine airplane couldn't maintain flight on just 
one engine, in most cases.  So, in his book, (We) Lindbergh stated that 
twin engines "gave twice as much chance of an engine failure."  The only 
thing two engines did, was to insure that you had enough power to make 
it to the crash scene.
Bill Glaze

Bob Pastorello wrote:

> Yeah, Tom, we're kinda back to why Lindberg didn't choose the twin 
> Bellanca...  I think he said "twice as many things to go wrong", or at 
> least that's my clouded recollection of the movie version...
>  
> Bob Pastorello
> NSRCA 199  AMA 46373
> rcaerobob at cox.net <mailto:rcaerobob at cox.net>
> www.rcaerobats.net <http://www.rcaerobats.net>
>  
>  
>
>     ----- Original Message -----
>     From: Tom Simes <mailto:nsrca at shinymetalass.com>
>     To: discussion at nsrca.org <mailto:discussion at nsrca.org>
>     Sent: Monday, January 24, 2005 4:28 PM
>     Subject: Re: any merit in running dual battery packs ?
>
>     On Mon, 24 Jan 2005 14:45:32 -0500
>     "Dean Pappas" <d.pappas at kodeos.com <mailto:d.pappas at kodeos.com>>
>     wrote:
>
>     > LEDs have large voltage drops. Something more interesting would have
>     > to be done. You have to figure out what is most likely to fail. My
>     > high-falutin' analysis, done ages ago, showed that switches and
>     > connectors are the worst culprits. I use one battery withtwin leads,
>     > and cvarry the twin leads all the way to the RX. Of course, I don't
>     > buy the cheapie batteries. Hello SR! Dean
>
>     So I can see that your method likely reduces the probability of
>     failure,
>     but as far as I can see you still have no indication that a
>     failure has
>     occurred in the primary system until a failure occurs in the secondary
>     system as well - although when the notification occurs it's a doozy!
>
>     Checking Digikey it looks like even the high efficiency LEDs are
>     still in the neighborhood of 2 V forward drop and the drop is fairly
>     consistent across their operating current range (darn physics!). 
>
>     It looks like one might be able to use something in the TI
>     TPS61010 thru
>     TPS61016 family to drive the LED (although obviously at the cost of
>     increased input current).  Or what about using a dropping resistor and
>     tapping the current flow downstream of the regulator with the lowest
>     voltage setting?  Should I crawl back in my hole with this?  I'm just
>     thinking that some kind of visual failure indicator would really be
>     a beneficial addition to a two pack design.
>
>     Of course that wouldn't show you that the backup pack had a failure
>     while the primary pack was still operating...  Although you could have
>     an LED on both regulators and as long as the expected one was on...
>     Vague memories of statistics class, MTBF calculations and the
>     effect of
>     adding components to a system are starting to crop up about now...
>
>     Nevermind, straight back to my hole it is - now where did I put that
>     tinfoil hat?
>
>
>     Tom
>
>     _____________________________________________________________________
>
>            |  ,  |               Tom Simes
>     ---------(@)---------        AMA 230068
>             --|--                NSRCA 3830
>               '                  nsrca at shinymetalass.com
>     <mailto:nsrca at shinymetalass.com>
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