any merit in running dual battery packs ?

[Ron Van Putte]

On Jan 24, 2005, at 5:40 PM, 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...

Yeah, that's what the Air Force pilots tell the Navy pilots on the 
merits of the F-16 vs the F-18.

Ron Van Putte

> Bob Pastorello
> NSRCA 199  AMA 46373
> rcaerobob at cox.net
> www.rcaerobats.net
>  
>  
> ----- Original Message -----
>  From: Tom Simes
> To: 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> 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
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