HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 26, 2011, 10:57 AM
Since 1952
Harry D's Avatar
Canada, AB, Edmonton
Joined Oct 2004
1,371 Posts
Here are a few IR readings on some GensAce packs I did a couple of weeks ago, using Wayne's meter :

3S1300 - Cells: 7.96 7.52 7.68 Total = 23.16 FOM =1.20
3S1500 - Cells: 6.80 6.64 6.84 Total = 20.28 FOM = 1.18
3S5500 - Cells: 1.88 1.92 1.84 Total = 5.64 FOM = 1.16

Temperature was 20C.

I bought these packs about two months ago. The 5500 mAh pack was "as received". The others have had a dozen or so cycles (by normal flying).

The low IR values are confirmed by CBA discharge tests and flying experiences. Truly remarkable packs.

These are their so-called 25C packs. (I forgot to mention that, as I never pay any attention to any manufacturer's stated C values because IME those numbers are completely meaningless.)
Harry D is offline Find More Posts by Harry D
Last edited by Harry D; Jul 26, 2011 at 01:39 PM. Reason: Added info
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 26, 2011, 04:14 PM
Registered User
Rugby, UK
Joined Feb 2007
898 Posts
Quote:
Originally Posted by Harry D View Post
Here are a few IR readings on some GensAce packs I did a couple of weeks ago, using Wayne's meter :

3S1300 - Cells: 7.96 7.52 7.68 Total = 23.16 FOM =1.20
3S1500 - Cells: 6.80 6.64 6.84 Total = 20.28 FOM = 1.18
3S5500 - Cells: 1.88 1.92 1.84 Total = 5.64 FOM = 1.16

Temperature was 20C.

I bought these packs about two months ago. The 5500 mAh pack was "as received". The others have had a dozen or so cycles (by normal flying).

The low IR values are confirmed by CBA discharge tests and flying experiences. Truly remarkable packs.

These are their so-called 25C packs. (I forgot to mention that, as I never pay any attention to any manufacturer's stated C values because IME those numbers are completely meaningless.)
Well done Harry; it looks as if Gens Ace packs are good,and, just as important, consistently good as the FOM results show. An average of 1.18 for FOM is very good, particularly at 20Deg.Cent.
Some of the Nanotechs are good and some are not, but as with so many lipos it really is a lottery which puts me off.
Interesting that the FOM is consistent, irrespective of pack capacity which also supports Mark's original proposal in using it as a measure of lipo performance.
I don't have the brass face, but it would be interesting to ask someone in a hobby shop trying to sell you lipos if they would mind you testing them with the meter before buying as it literally only takes a few seconds. I guess the love and travel advice would probably be flying!

Wayne
Wayne Giles is online now Find More Posts by Wayne Giles
Reply With Quote
Old Jul 31, 2011, 02:53 PM
Registered User
The Netherlands, LI, Venray
Joined Dec 2008
1,405 Posts
Quote:
Originally Posted by Harry D View Post
Here are a few IR readings on some GensAce packs I did a couple of weeks ago, using Wayne's meter :

3S1300 - Cells: 7.96 7.52 7.68 Total = 23.16 FOM =1.20
3S1500 - Cells: 6.80 6.64 6.84 Total = 20.28 FOM = 1.18
3S5500 - Cells: 1.88 1.92 1.84 Total = 5.64 FOM = 1.16

Temperature was 20C.

I bought these packs about two months ago. The 5500 mAh pack was "as received". The others have had a dozen or so cycles (by normal flying).

The low IR values are confirmed by CBA discharge tests and flying experiences. Truly remarkable packs.

These are their so-called 25C packs. (I forgot to mention that, as I never pay any attention to any manufacturer's stated C values because IME those numbers are completely meaningless.)
Total is sum of IR of the cells, so not the measured pack IR with the ESR/IR meter

question what means FOM ?
jaccies is offline Find More Posts by jaccies
Reply With Quote
Old Jul 31, 2011, 02:58 PM
BrainFart RC-Pilot
TreeDiver's Avatar
Echt, Netherlands
Joined Aug 2003
3,159 Posts
Indeed, I also did wonder...what does FOM mean.

Today I did messure the 30C Rhino 1000mAh of 2 years old.
After charge they had 10mOhm/10mOhm/11/mOhm per cell.
Nice value IMO for a 1000mAh pack!
TreeDiver is online now Find More Posts by TreeDiver
Reply With Quote
Old Jul 31, 2011, 03:17 PM
Since 1952
Harry D's Avatar
Canada, AB, Edmonton
Joined Oct 2004
1,371 Posts
"FOM" means the "Figure of Merit" proposed by Wayne Giles (originator of the IR meter) which he developed based on a suggestion by Mark Forsyth. http://www.rcgroups.com/forums/showthread.php?t=1392662

The total of the individual cell IR values is more accurate than the measured pack IR. Wayne's meter determines cell IR using a true Kelvin measurement, so the resistance of the tabs, wiring, connectors etc is cancelled.

All of these factors are discussed in the thread referenced above, and earlier in this thread.
Harry D is offline Find More Posts by Harry D
Reply With Quote
Old Aug 08, 2011, 07:46 AM
Registered User
United Kingdom, Scotland, Mauchline
Joined May 2011
29 Posts
Hi Wayne, do you have any available meter? Are the prices still holding initial post? Thanks
jcmiguel is offline Find More Posts by jcmiguel
Reply With Quote
Old Aug 08, 2011, 09:48 AM
Registered User
Rugby, UK
Joined Feb 2007
898 Posts
Quote:
Originally Posted by jcmiguel View Post
Hi Wayne, do you have any available meter? Are the prices still holding initial post? Thanks
Not at present , unfortunately.
At present I am looking at a slight redesign to try to make the unit cheaper to produce as the present unit hardly breaks even financially. I don't therefore have any left but David Gray at ProgressiveRC has a stock.

See: http://www.progressiverc.com/esr-meter.html

Wayne
Wayne Giles is online now Find More Posts by Wayne Giles
Reply With Quote
Old Aug 11, 2011, 07:12 AM
Registered User
United Kingdom, Scotland, Mauchline
Joined May 2011
29 Posts
Thanks. Unfortunately, derivery from progressivecr will be a killer as I am in UK. I will wait then.
jcmiguel is offline Find More Posts by jcmiguel
Reply With Quote
Old Aug 11, 2011, 08:03 AM
Registered User
N2UMK's Avatar
Clifton, VA
Joined Mar 2003
87 Posts
HI. I have a couple xmitter 3 cell lipo packs that have internal resistance of 4.1, 3.8, 280.1; cell 1 , 2, 3 respectively. Yes, 280 milliohms for cell #3. They are new. Have only been charged 2 or 3 times on an FMA lab 8. They are a "blue lipo" and a "zippy".
This seems to be "normal" although I only the 2 packs. Is this high of internal resistance an issue or nothing to worry about?
Any comments? Why are they not more equal?
Thanks.
Pat
N2UMK is offline Find More Posts by N2UMK
Reply With Quote
Old Aug 11, 2011, 08:07 AM
BrainFart RC-Pilot
TreeDiver's Avatar
Echt, Netherlands
Joined Aug 2003
3,159 Posts
Quote:
Originally Posted by N2UMK View Post
HI. I have a couple xmitter 3 cell lipo packs that have internal resistance of 4.1, 3.8, 280.1; cell 1 , 2, 3 respectively. Yes, 280 milliohms for cell #3. They are new. Have only been charged 2 or 3 times on an FMA lab 8. They are a "blue lipo" and a "zippy".
This seems to be "normal" although I only the 2 packs. Is this high of internal resistance an issue or nothing to worry about?
Any comments? Why are they not more equal?
Thanks.
Pat
280? for cell 3?

That looks more like an error reading....or a 'very bad' cel
TreeDiver is online now Find More Posts by TreeDiver
Reply With Quote
Old Aug 11, 2011, 08:20 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
6,877 Posts
Or a bad connection on one balance wire.

Is the pack IR roughly a bit more than the sum of the 3 cells?

Quote:
Originally Posted by TreeDiver View Post
280? for cell 3?

That looks more like an error reading....or a 'very bad' cel
jj604 is online now Find More Posts by jj604
Reply With Quote
Old Aug 11, 2011, 10:36 AM
Registered User
Rugby, UK
Joined Feb 2007
898 Posts
Quote:
Originally Posted by N2UMK View Post
HI. I have a couple xmitter 3 cell lipo packs that have internal resistance of 4.1, 3.8, 280.1; cell 1 , 2, 3 respectively. Yes, 280 milliohms for cell #3. They are new. Have only been charged 2 or 3 times on an FMA lab 8. They are a "blue lipo" and a "zippy".
This seems to be "normal" although I only the 2 packs. Is this high of internal resistance an issue or nothing to worry about?
Any comments? Why are they not more equal?
Thanks.
Pat
Pat,
What are you measuring the IR with - presumably not one of my meters as the cell range is 30milliohms full range although they will read up to about 40 milliohms? If both packs are reading these sort of values then I would assume that the fault is in the measurement or leads.
The only other possibility I can see is that the packs might have a low rated fusible device in series with cell 3 because they are intended for transmitter use (??)

Wayne
Wayne Giles is online now Find More Posts by Wayne Giles
Reply With Quote
Old Aug 16, 2011, 06:20 PM
Registered User
N2UMK's Avatar
Clifton, VA
Joined Mar 2003
87 Posts
Hi guys. I'm using FMAs powerlab 8. Lipos r for xmitter use only. For a 6S pack the IR readings range from 4.x to 5.x (all 6 cells). Find it odd that both packs have a high IR reading on the 3rd cell. I'm pretty sure that 280.1 is what it read. I will double chk connections and the readings at the next charge.
Thanks for the replies.
Pat
N2UMK is offline Find More Posts by N2UMK
Reply With Quote
Old Aug 19, 2011, 06:07 AM
Registered User
Rugby, UK
Joined Feb 2007
898 Posts
Quote:
Originally Posted by N2UMK View Post
Hi guys. I'm using FMAs powerlab 8. Lipos r for xmitter use only. For a 6S pack the IR readings range from 4.x to 5.x (all 6 cells). Find it odd that both packs have a high IR reading on the 3rd cell. I'm pretty sure that 280.1 is what it read. I will double chk connections and the readings at the next charge.
Thanks for the replies.
Pat
Pat,

If I am understanding correctly, you are measuring a Tx pack (Presumably 3S?) and also measuring a normal 6S pack as well and in both cases Cell 3 is reading 280milliohms? If this is true then almost certainly the measuring device or the interconnection is faulty as John suggested. The 280 reading is almost certainly the max reading that the charger can read, so that any overange will read that value.

Wayne
Wayne Giles is online now Find More Posts by Wayne Giles
Reply With Quote
Old Aug 19, 2011, 07:18 AM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,839 Posts
Post #189

Quote:
HI. I have a couple xmitter 3 cell lipo packs that have internal resistance of 4.1, 3.8, 280.1; cell 1 , 2, 3 respectively. Yes, 280 milliohms for cell #3. They are new. Have only been charged 2 or 3 times on an FMA lab 8.

#193

Quote:
Hi guys. I'm using FMAs powerlab 8. Lipos r for xmitter use only. For a 6S pack the IR readings range from 4.x to 5.x (all 6 cells).
Reads to me problem is with Trans. LiPolys only. Most likely some type of circuite in the pack that is causing this.

FWIW I have a total of six FMA chargers which read IR and they are all extremely close to one another and aalso just happen to closely match results obtained by other using Wayne's meter.

Charles
everydayflyer is online now Find More Posts by everydayflyer
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Best fo the West Jets Schwemmer Inland Slope Rebels 0 Oct 14, 2010 06:02 PM
Discussion Motor fo UH Haoye EDF Ducted Fan Unit 7 Blade 3.5inch RJPIoW Electric Ducted Fan Jet Talk 1 Sep 08, 2010 01:05 PM
Question New Low IR Lipos Cells nxtdoor High Performance 75 Sep 06, 2009 05:47 PM
Discussion ESR meter to test Nicad/NiMH ?? 1101 DIY Electronics 3 Jun 15, 2009 05:08 AM