any merit in running dual battery packs ?

[Bob Pastorello]

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
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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