[NSRCA-discussion] IR meter

Mon Mar 30 03:41:27 AKDT 2009

Hey Ron,

I'd like the information please.

JLK

From: vanputte at cox.net
Date: Mon, 30 Mar 2009 07:07:55 -0400
To: nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] IR meter

About two years ago I reported on the Lipo Doc, which a friend of mine had designed, to measure cell internal resistance.  It uses two volt meters (you can use one, but two is easier).  I built one for myself and sent the plans/schematic to several people.  A couple of my club members built them and I rewired up one that Emory Schroeter had butchered.  I think Earl Haury made one as well.  

It is very inexpensive and all parts can be purchased at Radio Shack.  The problem is that you have to make it yourself and in this ARF-only society, only the avid individual will tackle the job.  I will send the information to anyone who's interested, but be forewarned that it takes about two hours to completely fabricate.

Ron Van Putte

On Mar 30, 2009, at 1:53 AM, krishlan fitzsimmons wrote:

Interesting. Well, maybe someone will come up with a good one at some point for those that don't use a Cellpro. I can't say my Cellpro is accurate, just that it works and gives me something to base my batteries off of. 

Jim, 

Any idea why 2 and 3 cell packs have such a high resistance? Even new mine are over 20. Hard to tell when they are bad. 

Something interesting is that on my AFPD sim, I was just flying the Spark. I haven't flown it much as there are a few things I don't care for compared to others that I have on there. One was that it felt underpowered. An easy change normally, just never did it. But instead of altering the motor, I went and looked into the batteries. The resistance was set at 13.0. I changed it to 2.0 and now the plane it silly fast. Not sure that means anything, just found it interesting. 

Thanks, 

Chris 

--- On Sun, 3/29/09, AtwoodDon at aol.com <AtwoodDon at aol.com> wrote:

From: AtwoodDon at aol.com <AtwoodDon at aol.com>
Subject: Re: [NSRCA-discussion] IR meter
To: nsrca-discussion at lists.nsrca.org
Date: Sunday, March 29, 2009, 9:27 PM

I agree, since I have to charge anyway, I am going to believe the CellPro.  I sold the IRM to someone that was unhappy they were sold out when he went to order......  

D

In a message dated 3/29/2009 8:31:52 P.M. Pacific Daylight Time, joddino at socal.rr.com writes:
Don, 

I would say the FMA is closer to the real value.  I'll look at some inflight data but just as a test of reasonableness I looked at the data I sent you recently where I was pulling about 98 Amps at 39 volts.  My pack has about 3 mOhms per cell according to the FMA times 10 cells is .03 Ohms for the pack.  98 x .03 = 2.94 volts  If the resistance was 7 times higher the drop would be seven times higher or around 21 volts.  Something is wrong with his algorithm. 

Jim

On Mar 27, 2009, at 5:22 PM, atwooddon at aol.com wrote:

I have one, caught the discussion thread just as it started and jumped on the initial orders.  It works as expected. Although the IR numbers are substantially higher than what the FMA charger reports the relationship of the IR numbers between the cells is  proportionately the same.  The IRM shows IR ohms about 7-8 times that of the FMA CellPro 10S.  Which one is right?  I dunno, but when I asked why they were so different, I got a very long explanation that I did not understand.  All I know is the ratios seem to stay the same between them on the same batteries.  

It is well made tho I don't care for the small plugs for balance taps, that is kinda clumsy, but it works as advertised.

Don

In a message dated 3/27/2009 11:55:58 A.M. Pacific Daylight Time, homeremodeling2003 at yahoo.com writes:

Did you guys see this yet? Could be helpful if your charger doesn't do it. 

http://www.rcgroups.com/forums/showthread.php?t=980290

Chris 

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