[NSRCA-discussion] AAA NimH batterys

[Dean Pappas]

Hi Gang,
Don't equate the typical NimH with horrible cell resistance to the good ones with low resistance. They really are different animals. Look at the "H" series on the SR site, then compare cell resistances. In most cases, you can't even find the numbers, on most cells you buy, because they are so horrible. Don't throw the baby out with the bath-water.
Low resistance NimH cells are, no doubt, available from elsewhere, too. I'd check NoBS batteries first.
Dean

	-----Original Message----- 
	From: nsrca-discussion-bounces at lists.nsrca.org on behalf of Jerry Budd 
	Sent: Sat 1/28/2006 4:02 AM 
	To: NSRCA Mailing List 
	Cc: 
	Subject: Re: [NSRCA-discussion] AAA NimH batterys
	
	

	For the 2002 Nats I switched to a AAA 700 mAh NiMH battery pack to
	make weight.  While practicing at the Kokomo field I discovered that
	the pack was good for about 1-1/2 flights (don't ask me how I know
	that!).
	
	Fortunately, I got control back (well - partially) after the 1-1/2
	downline snap and was able to coax the plane back onto the ground.
	Not fun.
	
	At the post-flight debrief I figured out that the AAA cells simply
	had too high of an internal impedance to deliver enough current to
	keep the voltage above the receiver/servo cut-off level when all the
	servos needed to move at once.  I was using JR 7000 Super Servos for
	aileron which went slow/shut off at 4.6V whereas the other JR servos
	kept on working down to 4.2V.
	
	Jerry
	
	
	>Ed is right.  The smaller the cells the higher the internal resistance.  Run
	>them down to 20% remaining capacity and put a heavy load, like 5 Amps on
	>them and read the voltage.  You will probably not like what you see.
	>
	>Jim O
	>
	>
	>----- Original Message -----
	>From: "Ed Alt" <ed_alt at hotmail.com>
	>To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
	>Sent: Thursday, January 26, 2006 3:06 PM
	>Subject: Re: [NSRCA-discussion] AAA NimH batterys
	>
	>
	>>  Ed:
	>>  You might get disappointing results due to the inherently high internal
	>>  resistance of NiMH.  Going with AAA cella and such a low capacity might
	>mean
	>>  that you don't get as many flights as you expect before a voltage test
	>under
	>>  load dips below an acceptable value.
	>>
	>>  Ed
	>>  ----- Original Message -----
	>>  From: "Ed Miller" <edbon85 at charter.net>
	>>  To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
	>>  Sent: Thursday, January 26, 2006 9:05 AM
	>>  Subject: [NSRCA-discussion] AAA NimH batterys
	>>
	>>
	>>  > Is anyone using AAA NimH batteries for a RX pack ??. I am looking at
	>>  > Batteries America ( EHYOST ) and they seem to have AAA NimH's in 720,
	>800
	>>  > and 900mah ratings. I currently use their 2/3A 5 cell NimH pack at
	>1100mah
	>>  > and a weight of 3.85 ounces complete with the long lead I have on the
	>>  > pack.
	>>  > Going to their AAA 5 cell pack looks like I can save about an ounce or
	>so.
	>>  > Mah isn't an issue, I can get in excess of 7 to 8 flights on the 1100mah
	>>  > pack I use now before charging so going to 900mah shouldn't be a big
	>hit.
	>>  > Don't suggest Lithium anything as lighter, want to continue to use my
	>>  > Alpha
	>>  > 4 charger and am not convinced those new batteries are safe.
	>  > > Ed M.
	
	--
	___________
	Jerry Budd
	Budd Engineering
	(661) 722-5669 Voice/Fax
	(661) 435-0358 Cell Phone
	mailto:jerry at buddengineering.com
	http://www.buddengineering.com
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