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Old Feb 05, 2011, 11:40 AM
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IR of new Nano Techs

I bought two new 3S2200.25C Turnigy nano tech packs from HC for use, not testing and came to check them yesterday.
They are both balanced but they show surprisingly high IR values so I did a proper comparison at controlled temperature (25deg.C) and here are the results compared with other packs I have:-


Pack Type---------------Cell 1-Cell2-Cell3---Pack
Nanotech 2200.25C----13.2--12.3--13.7---39.1
LoongMx 2250.25C-----6.8----7.6---7.2---21.6
Turnigy 2200.25C------4.8----4.9---5.1---14.8
Nanotech 2200.45C----4.9----5.1---4.8---14.8

The Loong Max and normal Turnigy are both 2 years old and well used, whilst both the Nanotechs are new. I also have a 1300.25C nanotech which is only cycled but totals 27.4 milliohms which is 30% better than both the 2200.25C nanotechs.
The only reason I can see is that they may improve with cycling, but if they are to be any good they have a long way to go.
I will cycle them and update this thread.

The other oddity is that the old 25C Turnigy shows identical results to the new high tech. 45C Nanotech! It certainly is capable of a full 25C continuous discharge because I have done one.
I would be very surprised if the Nanotech is capable of a full rated discharge.

Wayne
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Old Feb 05, 2011, 12:15 PM
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FWIW Link to my 3S 2200 Nano 45 test. IRs on fourth attachment (bottom of post)

http://www.rcgroups.com/forums/showp...95&postcount=1

Update With 36 cycles at 80% state of charge (all cells at 4.025V) 74F IRs 6.2 / 5.0 / 5.0

Charles
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Old Feb 05, 2011, 02:18 PM
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Not horrible but certainly not noteworthy performance by any means. Admittedly, real life differences would be subtle except in high performance planes and helis.

Just goes to show that all a manufacturer needs to do is to append 'Nano' to any product and it'll fly off the shelves, regardless of actual measurable performance.

Your 2-year-old Loong Max and Turnigy's are outstanding and have very obviously been well-cared-for.

Mark
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Old Feb 05, 2011, 03:56 PM
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Originally Posted by mrforsyth View Post

Your 2-year-old Loong Max and Turnigy's are outstanding and have very obviously been well-cared-for.

Mark
Not true actually Mark, I'm ashamed to say; they were tested at full rated discharge several times down to 3V/cell and have done some flying but not more than about 50 cycles each. During testing I pulled them apart and found they were the same cells interconnected with the same coded PCB. See attached photo - LM on left and Turnigy on right.

Wayne
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Old Feb 05, 2011, 07:08 PM
"Comin down Fast"
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Ain't it amazing? A half ounce of solder for the balance lead connections and the LongMax on the left has the yellow still screaming for attention , garbage.
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Old Feb 05, 2011, 08:56 PM
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Not true actually Mark
I stand corrected. Even more impressive given that they have seen some abuse. I trust that these two packs have been at least stored in a friendly environment (discharged and in cool location).

Mark
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Old Feb 06, 2011, 01:35 PM
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I stand corrected. Even more impressive given that they have seen some abuse. I trust that these two packs have been at least stored in a friendly environment (discharged and in cool location).

Mark
It is me who should be corrected Mark, probably sent to a "Lipo Treatment Correction Establishment" as although I am aware of what I should do, I never get round to it. Every winter I intend to discharge all my lipos to 3.85V etc but have yet to do it. They have been stored in an old fridge (not working) in an outbuilding so they have not fallen below freezing (I think) but have been fully charged or near.
They have not been abused by overcharge/discharge so it makes one wonder. Some Lipos seem to last no time however you treat them and others seem bulletproof, not necessarily a function of cost. Both those packs were very cheap and perform really well (they are the same cells) - I only noticed because I was doing a comparitive discharge and the two plots could be overlaid and looked like one plot which is what made me pull them apart to check.

Wayne
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Old Feb 07, 2011, 09:08 AM
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Originally Posted by mrforsyth View Post
Not horrible but certainly not noteworthy performance by any means. Admittedly, real life differences would be subtle except in high performance planes and helis.
Mark
Not convinced about that Mark, I have now cycled the 3S2200 25C Nanotech (5 cycles at 1C charge and discharge) and there is no significant change in IR.
I would expect the cell IR to be around 6 - 7 milliohms, so with it at 12 the pack is 36 instead of 20milliohms.
I see your comment about not getting too hung up on IR, although I do have a specific interest. I have done sufficient load testing to be fairly sure that the flight performance of a 3S.2200 pack which starts with an IR of >35milliohms is going to be fairly disappointing.
Operating at 15C, say, would equate to a voltage difference of about 0.53V which is 5% so we would see about 10% less power which is very noticeable.
The other reason I question it is the fact that I have a 3S1000.20C Loong Max and a 3S1300.25C Nanotech which both have lower IRs than this latest 2200 'High-Tech' pack

Wayne
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Old Feb 07, 2011, 10:56 AM
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Agreed that the 25C Nanotech exhibited very poor performance - roughly equivalent to some 16C packs that I purchased at my LHS several years ago (assuming roughly similar accuracy in our measurement devices / techniques). These will obviously have significantly poorer performance than the other packs.

Even more disturbing is the fact that your 1300mAh 25C Nanotech had well less than 1/2 the IR of the new 2200mAh Nanotech when normalized for capacity. Since the cells in the new pack were quite consistent the poor pack IR cannot be attributed to a bad cell. It is simply a lousy pack.

My comment above was aimed at the 45C Nanotech pack that you measured (I admittedly wasn't clear about that). These IR numbers are more in the ballpark with some of my higher performance packs and I doubt that I personally would be able to tell any difference in my particular planes.

Mark
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Old Feb 08, 2011, 10:15 AM
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IRs cool LiPolys

I decided to check IR of a few 3S 2200 LiPolys using one of my POWERLAB8 but at a much lower charge rate than I normaly use. All were at 3.85 per cell and had been setting over night or longer. All were at 68-69 F and were charged at .5A in order to prevent cells from being warmed up.

Thunder Power Pro Power 65 56 cycles 4.9 / 4.9 / 4.9 (@90F less than 2)
25C Blue 23 cycles ------------------------ 9.5 / 9.1 / 9.1
Turnigy Nano 45C 38 cycles --------------7.8 / 7.8 /7.8

Added: Placed ProPower65 back on cycler and charged at 15A temp. increased to 82F IR 3.1 / 2.5 / 2.5


Charles
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Old Feb 08, 2011, 03:37 PM
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Start, End or what?

Regarding IR; I undertand the number changes during charging. So which one is the more representative IR, the one at the end of the charge?
I have a Powerlab 8, it it makes any difference.
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Old Feb 08, 2011, 03:51 PM
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It only changes during charging if the temperature of the cells change.

Quote:
more representative
of what?

I am a die hard believer in discharge test (graphs) as a means to measure a LiPolys performance.

Most, I feel should use IRs as a guide / comparison . However you want to obtain the results just be consistent.

Overall lower is better but only if the capacity and the temperature is the same.

Charles
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Old Feb 08, 2011, 04:47 PM
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Originally Posted by everydayflyer View Post
Most, I feel should use IRs as a guide / comparison . However you want to obtain the results just be consistent.
I agree with Charles, watching a trend is better than the actual number. To do that, I use the same device to measure, same temp, and same voltage when I log this data. The actual number means little to me, unless I have a comparison to other packs, or even the same pack over time. Then I know when something is changing, regardless of what the actual number reads.
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Old Feb 08, 2011, 05:26 PM
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Originally Posted by everydayflyer View Post
It only changes during charging if the temperature of the cells change.

I am a die hard believer in discharge test (graphs) as a means to measure a LiPolys performance.

Most, I feel should use IRs as a guide / comparison . However you want to obtain the results just be consistent.

Overall lower is better but only if the capacity and the temperature is the same.

Charles
I agree Charles but many people can't be bothered to read a discharge plot in detail.
IR is therefore a spot figure that gives a good indication of performance, but as you say it is essential that the temperature must be consistent (say 25C/77F) and the pack must be allowed to settle at the temperature after charge/discharge if the results are to be valid. To just take a reading from a charger at any charge current is fairly meaningless.
Agree with Eric also; it really is a comparitive tool, a useful guide between packs and indicative of problems if it rises on a single pack.
I will try to run a discharge plot on the two 25C Nanotechs and compare them with some other packs. Not a single rogue pack as they both measure the same

Wayne
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Old Feb 08, 2011, 06:36 PM
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I agree Charles but many people can't be bothered to read a discharge plot in detail.
That, coupled with the fact that it's far easier to understand a discrete number than it is to interpret a compound curve which has many variables. It's for this reason that the completely arbitrary and utterly useless 'C' rating is nearly universally accepted as a means of comparing quality among the various manufacturers. And the manufacturers aren't complaining as they merely slap a big 'C' number on their wares and laugh all the way to the bank...

Rant off.

Mark
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