[NSRCA-discussion] FW: Resistance and retirement

Mon Nov 10 16:08:11 AKST 2014

Ooops, I actual meant to send this e-mail to the group!
Mike C

From: precisionaero at hotmail.com
To: vincebrc at gmail.com
Subject: RE: [NSRCA-discussion] Resistance and retirement
Date: Mon, 10 Nov 2014 18:07:30 -0700

The issue I am having is with some packs I use for an EDF. Under the "load" of takeoff, two of the three packs I use noticeably sag.  I took off after the sag the first time and was able to make it around  for a landing, but I don't think I took a breath the whole time.  I topped off the packs and ran them on the ground and could hear the sag then too.  I did not hook up my watt meter in line because the watt meter has Deans connectors and the EDF has 5.5mm bullets.  I did cycle both packs on the chargers and they had about 3 to 4 mOhm resistance on 5 of the 6 cells with one pack having a 6 mOhm resistance and the other 12.5 mOhm resistance on an individual cell.  I guess I am surprised the higher resistance on one particular cell could cause a problem, but I know the EDF systems hit the batteries really hard.  Any thoughts on why I am seeing an issue?  Is it related to the higher resistance?  Is there some device out there that tests individual cells under a discharge load?
Mike C   

Date: Mon, 10 Nov 2014 11:02:18 -0600
To: chuenkan at comcast.net; nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] Resistance and retirement
From: nsrca-discussion at lists.nsrca.org

I use TP.  The IR is usually around 2-3 when new.  I usually use them for practice and contest until around IR gets around 5.  Over 5 I start to feel the power loss and I don't use those anymore.  I don't like to take the smoke risk.  In general, I get around 80-100 cycles.   
Vicente "Vince" Bortone

On Mon, Nov 10, 2014 at 9:18 AM, Phil S. via NSRCA-discussion <nsrca-discussion at lists.nsrca.org> wrote:

Yes, Dan, these things work on the Smooke Principle
-- if you let the white smoke out, they quit working...

Phil Spelt, KCRC Emeritus, Secretary
AMA 1294 Scientific Leader Member
SPA L-18, Board Member
(865)435-1476v, (865)604-0541c

On 11/9/2014 5:47 PM, Dan Curtis via NSRCA-discussion wrote:

  Ah, flag, that is where I was making my mistake.  I
thought it was white smoke.

  Dan

    On Sunday, November 9,
2014 4:42 PM, Ed White via NSRCA-discussion
<nsrca-discussion at lists.nsrca.org> wrote:

  I don't go by IR differences. I eventually reach a
point that in a practice flight I pull up for the last maneuver in the
sequence and the battery puts up a little white flag and says, "not
gonna happen".  Then I retire the pack.

Ed

  On Sat, Nov 8, 2014 at 1:56 PM,
Michael Cohen via NSRCA-discussion <nsrca-discussion at lists.nsrca.org>
wrote:

    Is there any rule of thumb for how much difference
between individual cell resistances is OK before a back should be
retired?

    Regards,
    Mike C

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