any merit in running dual battery packs ?

[Tom Simes]

On Mon, 24 Jan 2005 13:25:54 -0600
"Keith Black" <tkeithb at comcast.net> wrote:

> A backup battery can be done as described in Lance's article in the
> December K-Factor or there are other approaches that can be used. The
> method I use is two five cell packs, one primary (pick your battery
> type or size) and one a AAA 750 mha NiMH pack, both going through
> their own switch and regulator into different channels in the RX. The
> regulator on the primary battery is 5.8 volts and the regulator on the
> backup battery is 5.5 volts. This will cause the voltage to be drawn
> from the primary battery and not the backup battery. Voltage will only
> be pulled form the backup battery when the primary battery voltage
> drops below 5.5 volts. The regulators also perform the task of
> preventing reverse charging (like a diode). 

I understand and like elements of both Lance's and Keith's approach, but
one thing that I see missing is some easy to spot indication that the
primary pack has sustained a failure.  I know you could stick a meter on
the backup pack between each flight to see if it has discharged any, but
I was thinking of something that would stand out.

I'm not an EE, but do you think it would be possible to find a LED with
a low enough forward drop to be used for both preventing discharging as
well as an indicator that there is a condition requiring immediate
attention?  I'm thinking that if the LED is inline with the lower
capacity pack, it should only illuminate if current is flowing from that
pack in either Lance's or Keith's design - am I wrong?

-- 
Tom

_____________________________________________________________________

       |  ,  |               Tom Simes
---------(@)---------        AMA 230068
        --|--                NSRCA 3830
          '                  nsrca at shinymetalass.com
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