[NSRCA-discussion] Receiver packs

Sat Feb 14 12:45:55 AKST 2009

I appreciate these discussions as I'm switching over to lipos and this little exchange

has me feeling a little warmer and fuzzier.  And Jerry, there are some good small balancing chargers out there--FMA's Cellpro 4S for one--that are excellent for this application and shut off charging when done.  Now why aren't you watching the KU/K-State game?

Richard

PS Brian at Tanic will wire up a 780 with a Cellpro charging node and Futaba connector for like 27 bucks.

From: ed_alt at hotmail.com
To: nsrca-discussion at lists.nsrca.org
Date: Sat, 14 Feb 2009 16:26:08 -0500
Subject: Re: [NSRCA-discussion] Receiver packs

Jerry:
Using A123 batteries requires extra vigilance, since they have a very flat discharge curve for most of their capacity (after an initial quick drop), right up to the point where you have little usable capacity left.  As a result, you won't be able to gauge remaining capacity with a meter, although you can estimate it once you can experience with typical discharge characteristics.  As long as everything with your servo current drain remains consistent and healthy, you can pick a reasonable quitting point after X flights.  I'm not sure what the appeal of these batteries is for a flight pack application. One drawback is that you run the servos at a fairly high voltage, which might damage some servos.  If you add regulators, that problem is alleviated, but overall you have a heavier solution than with a LiPo set.  Enhanced charging safety is really all that you are buying.  

I think the thing that should be realized is that a set of 2 cell 480 or 730 mAh LiPo's have an extraordinarily easy life when all they are doing is powering a flight pack.  You can get many more cycles out of then than NiCad or NiMH packs and they have much better end of life performance.  I just don't see what the concern is.

Ed

----- Original Message ----- 

From: Jerry Voth 
To: General pattern discussion 
Sent: Saturday, February 14, 2009 4:11 PM
Subject: Re: [NSRCA-discussion] Receiver packs

Richard, 

I was thinking more about using A-123 batteries. They're supposed to be safer. My memory is what scares me about Lipos. 

Also, what would the effect be on an ESC using A-123 batteries in place of Lipos? I've read there are some issues. 

Jerry

----- Original Message ----- 
From: Richard Strickland 
To: General pattern discussion 
Sent: Saturday, February 14, 2009 12:37 PM
Subject: Re: [NSRCA-discussion] Receiver packs

Jerry--just a couple thoughts:  I will probably never use a battery for a receiver/flight pack again that I haven't been in charge of its history.  If you've been paying attention to its characteristics since new, we can generally tell when they start to lose capacity--and for me, there was a point on the ESV when it got there, I got a little nervous about going up 'one more time'.  When it would approach that point after about five flights, then I would figure it was 1. if early in its career--then to cycle and 2. if in to the second or third year(sometimes longer) it was time to retire it.  Nicads for me have been pretty reliable that way and I've been comfortable running one pack.  You can still go to five cells in nicads for additional capacity and power with a regulator and still have that reliability.  I think most of the guys that have gone to lipos can enjoy the increased capacity and power along with an increased discharge rate in a smaller, lighter package.  But I don't get the impression that they trust them like nicads.  Probably the best thing to do is monitor your batteries of any type with a good, loaded ESV to keep an eye out for any unusual battery behavior.  The two battery debate is a little like the single versus twin debate in full scale airplanes--some guys think twins just have double the chances to fail.
All that said, I understand some of the new receivers are a little touchy regarding low voltage situations.  I had an older receiver in an airplane that I bought used with a 'new' battery--turned out the battery was bad--but got a warning(hold) and was able to land--but showed NO volts afterward. 
Chances are with the newer stuff, it may not have made it back on the ground in one piece.  So using a 5 cell nicad or 2 cell lipo with regulator may not be a bad idea and monitor with a good loaded ESV.
FWIW
Richard

From: jjvoth at mtelco.net
To: nsrca-discussion at lists.nsrca.org
Date: Fri, 13 Feb 2009 20:32:46 -0600
Subject: Re: [NSRCA-discussion] Receiver packs

Thanks for the info guys

----- Original Message ----- 
From: Vicente "Vince" Bortone 
To: General pattern discussion 
Sent: Friday, February 13, 2009 8:28 PM
Subject: Re: [NSRCA-discussion] Receiver packs

Hi Jerry,

I have been using two li-po using the tech-aero double regulator http://www.tech-aero.net/plr5-dr2.htm  The capacity I am using now is 930 mah, 2 cells  batteries.  I know that I can fly at least 6-8 times.  After that, I am brain dead.

VB

----- Original Message -----
From: "Richard Strickland" <pamrich47 at hotmail.com>
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Sent: Friday, February 13, 2009 8:01:03 PM GMT -06:00 US/Canada Central
Subject: Re: [NSRCA-discussion] Receiver packs

Jerry, I think the short answer is no.  But there has been much discussion regarding dual packs for back-up.  An example ot single pack usage is using a 2 cell lipo at around 780-800ma for practice and 340-380ma for contests to make weight.  These are used with voltage regulators with variing outputs.
RS

> From: jjvoth at mtelco.net
> To: nsrca-discussion at lists.nsrca.org
> Date: Fri, 13 Feb 2009 17:32:25 -0600
> Subject: Re: [NSRCA-discussion] Receiver packs
> 
> Sorry, I said that wrong. I meant are two packs needed to power the flight 
> pack.
> ----- Original Message ----- 
> From: "Jerry Voth" <jjvoth at mtelco.net>
> To: "NSRCA" <nsrca-discussion at lists.nsrca.org>
> Sent: Friday, February 13, 2009 5:23 PM
> Subject: [NSRCA-discussion] Receiver packs
> 
> 
> > This has probably come up many times but I'd like to know if it's 
> > necessary
> > to use two Li-Fe packs for the radio and servos
> > _______________________________________________
> > NSRCA-discussion mailing list
> > NSRCA-discussion at lists.nsrca.org
> > http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
> >
> 
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