any merit in running dual battery packs ?

[Keith Black]

Tom, here's what I use. It plugs directly into the RX to show the voltage at
the RC. Before each flight I flip on one power switch, check the voltage,
turn it off then turn on the other power switch. This shows me the voltage
the RX is seeing from each power source.

http://www.i4cproducts.com/r_c_applicaltions.htm

NOTE: Since this is a regulated voltage (in my setup) the voltage shown is
not indicative of capacity of a 6 volt battery. To check the true voltage to
help see how discharged the battery is you would need to plug in a meter to
the charging line.

Keith

----- Original Message ----- 
From: "Tom Simes" <nsrca at shinymetalass.com>
To: <discussion at nsrca.org>
Sent: Monday, January 24, 2005 1:41 PM
Subject: Re: any merit in running dual battery packs ?


> 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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