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<DIV><FONT face=Arial size=2>Bob, your point about servo performance is true,
though I don't how significant it is in our application.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Here's an interesting point that I didn't mention
before. With my two packs, one regulated at 5.8 and one at 5.5, after
flying four flights the primary 1650 mah battery will take about 800
mah in charge and the backup 750 mah battery will take about 130 mah. Of the 130
mah I don't know how much is due to the nominal load going to the regulator/RX
and how much is actually going to the servos.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I thought this was quite interesting and proved to
me that the primary battery is providing the majority of the power. Another
thing that this setup does for you is if your backup battery ever requires a
larger than normal charge you know something is going wrong somewhere.
</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Keith Black</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=bob@toprudder.com href="mailto:bob@toprudder.com">Bob Richards</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, January 24, 2005 2:40
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: any merit in running dual
battery packs ?</DIV>
<DIV><BR></DIV>
<DIV>The redundant packs also have the possible benefit of improving
servo performance. With two packs *and the parallel wiring* you will have less
voltage drop and fluctuations when the servos are in a high-load, high-current
mode. It is entirely possible that you can be instantaneously drawing
several amps current during a flight, particularly during any maneuver
where multiple servos will be quickly deflected (like a snap roll). With
two packs you have less internal (battery) and external (wiring)
resistance.</DIV>
<DIV> </DIV>
<DIV>I have also noticed that on some servos if you have a 4 cell pack and you
lose one cell, the servos will stop working. I know this is true for the first
JR super servos. The regular servos continue to operate, although
slowly.</DIV>
<DIV> </DIV>
<DIV>I think there is merit to running two packs.</DIV>
<DIV> </DIV>
<DIV>Bob R.</DIV>
<DIV><BR><BR><B><I>Keith Black <tkeithb@comcast.net></I></B>
wrote:</DIV>
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<DIV>Though it's true that most planes flown use only one battery, and if
maintained correctly a pilot can go years without loosing a plane for power
reasons if he's lucky, there are still several failure points that can turn
a two to three thousand dollar model into firewood. I personally know
of at least four pattern planes that have been lost due to power issues. The
failure points include bad wiring, faulty regulator (if used), switch,
battery going bad, false peaks, battery becoming dislodged and unplugging,
and probably some others that I haven't thought of. </DIV>
<DIV> </DIV>
<DIV>I think having a backup battery is a very good idea if you can afford
the additional weight. I personally prefer the second battery even if it
makes me a few ounces over weight for the majority of my flying which is
practice. A centrally located backup battery can be removed for contests to
make the weight limit. </DIV>
<DIV> </DIV>
<DIV>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). </DIV>
<DIV> </DIV>
<DIV>This approach is slightly heavier than Lance's approach since it
requires two regulators and an additional cell, but for me it worked well
and was easy.</DIV>
<DIV> </DIV>
<DIV>Keith</DIV>
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