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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>
<DIV> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=Rcmaster199@aol.com
href="mailto:Rcmaster199@aol.com">Rcmaster199@aol.com</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 10:16
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: any merit in running dual
battery packs ?</DIV>
<DIV><BR></DIV><FONT id=role_document face=Arial color=#000000 size=2>
<DIV>
<DIV>In a message dated 1/24/2005 7:19:07 AM Eastern Standard Time, <A
href="mailto:hitesh@salt.ac.za">hitesh@salt.ac.za</A> writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=095360912-24012005>Hi,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=095360912-24012005></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=095360912-24012005>Now that we all using high powered digital servo's
with incredible holding power etc - is there any merit in running 2 battery
packs, say 1 Ah each as opposed to 1 high capacity pack thereby
eliminating the single point failure ? If I did want to run 2 packs, is a
diode necessary to prevent 1 pack from possibly charging the other if 1 pack
were to go bad ?</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=095360912-24012005></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=095360912-24012005>Cheers,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=095360912-24012005>Hitesh</SPAN></FONT></DIV></FONT></BLOCKQUOTE></DIV>
<DIV></DIV>
<DIV>Hitesh, a 1500 to 2000ma battery is all you need. There's little
advantage to redundancy unless you are planning to fly more than 5-7 flights
(res) on any given day. But then again, I use NiMH on the airborne and only
Sanyo packs, which have proven extremely reliable for several years now.
As such, a redundant power source isn't really necessary in pattern
models and you can avoid some unnecessary weight build up. </DIV>
<DIV> </DIV>
<DIV>What has been done in large models is to add another battery
and switch harness to an unused channel on the receiver, which provides
adequate redundancy. The extra weight on such models isn't as critical as it
is in pattern models. Both switches "on" at take-off please.</DIV>
<DIV> </DIV>
<DIV>Of course, if you just have to have the extra battery and you have enough
weight margin and room, the above is one way to do it. There are other ways,
but this is simple and reliable.</DIV>
<DIV> </DIV>
<DIV>MattK</DIV></BLOCKQUOTE></FONT></BODY></HTML>