any merit in running dual battery packs ?

[Keith Black]

That was supposed to be "to show the voltage at the RX...".

----- Original Message ----- 
From: "Keith Black" <tkeithb at comcast.net>
To: <discussion at nsrca.org>
Sent: Monday, January 24, 2005 3:04 PM
Subject: Re: any merit in running dual battery packs ?


> 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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