Posted: October/23/2006 at 9:37pm | IP Logged

Andrew, I have made several of my own battery packs... flight / receiver battery packs and transmitter packs.  The best place I have found to buy high capacity batteries is http://www.batteryspace.com  great prices and great shipping.  Aaron and I used to make big Zagi battery packs with their individual AA ni-mh batteries.  They now have very good prices on pre-built transmitter and receiver packs.  It's hard to beat the price even if you build them yourself.  Check out the site and see what you think.  You will be surprised.  I have used the pre-built packs in my big Comp-ARF Extra for 3 years now with very good luck.

There are other places on the internet where you can buy the shrink tubing etc.. to make your own packs... you can solder the batteries together or get batteries with tabs.

I'm sure some other NURCAC members might good input on this subject.

It's nice to have you asking the questions!  We all might learn something if we start to get some feedback on these topics.

Matt

Posted: October/24/2006 at 8:53pm | IP Logged

For most Ni-mh and Ni-cd AA size batteries... they are usually 1.2 volts per cell.  So if you put them in series, 4 cells would be 4.8 volts and 5 cells would be 6 volts etc...  if you put them in parallel then you multiply the battery's capacity and maintain the same voltage.

I just did a google search on the shrink tubing and found this site: http://members.aol.com/davthacker/radicalrcbatteries.htm#bp

Just poke around on the Internet and if you find a good site and order... post a message here and let everyone know.  You could also search on RCUniverse.com

mg

Posted: October/25/2006 at 7:08pm | IP Logged

Andrew, Steve Jacobson pointed out that I had parallel and series backwards in my earlier post... he was right, I updated the post.

The big reason 6 volts is popular over 4.8 volts is the fact that the servos will be faster at the higher voltage.  Usually you see the speed rating for both 4.8 and 6 volts.  Make sure your servos can handle 6 volts if you go this route... most are fine at 6 volts.

The negative for the 6 volt setup is weight as you mentioned and also another factor to think about is the fact that your batteries will actually drain faster running at 6 volts for the same capacity battery pack.  The previous paragraph is the key with the speed... if the servos are working faster due to higher voltage, they are drawing more current at the higher voltage so the same capacity battery at 4.8 volts will drain slower than the same capacity battery running at 6 volts.  Talk to your Dad, he can give you all the EE details about this. ;) Ohms law etc...  someone else might describe this better than I have here.

mg

Posted: October/28/2006 at 9:51am | IP Logged

Almost all electirc planes are now powered with lithium polimer (LIPO) batteries.  The electronic speed control will also supply the receiver with power (at 4.8 or 6 volts depending on how nice of ESC it is).  Because of this, electric plance typically don't have a receiver battery pack except for the very large glow/gas converted planes that have high servo counts.

It would be nice to run the smaller/lighter LIPO packs as a receiver battery but a two cell LIPO battery runs at 7.4 volts and should only be used with a voltage regulator that will drop the voltage.  The voltage regulators add weight and complexity so there is a trade off...