Originally Posted by bigroger

I also just received several hundred dollars worth of various gens ace packs and all of the 3s packs read IR numbers over 12 and in one case over 20 mOhm on my iCharger.
I also received several 4s2600 gens ace packs in the same delivery that measure 2-3mOhm on first charge.

Very disappointing as this was a major purchase to upgrade my turnigy 3s1600 with GA 3s1550 and a set of five GA 3s2200 that are all way below the 25C rating.

I will endeavor to send these back to the UK supplier for refund, but as I have changed the battery plug over I suspect I will be plumb out of luck.

I too contacted the vendor explained the situation and attached the readings posted in the other thread. I did get a response but only from someone saying they will pass the message on to the guy that does their buying and they hadn't had any other bad reports of them. No hint or suggestion that I could get a refund or exchange on them. I will give it a while and see if I hear from the buyer and will contact them again if I don't in a reasonable time scale. I don't want to be too harsh on the vendor which is why I haven't mentioned who it is, after all it isn't caused by them, but it would be their job to sort out the problem with Gens Ace and find out if they are going to stand by their product and try and live up to the good name they built themselves.

I wonder how many are manufactured in a batch? could it be a case that some vendors might get good one's and others unfortunately not so lucky?

Is the ESR meter that is sold through ProgressiveRC more accurate than an iCharger 3010?

I ask this because I have a pack that is showing 1's and 0's on my iCharger. Seems like the resolution of the reading is just not fine enough on these higher C packs.

Originally Posted by Melnic

Is the ESR meter that is sold through ProgressiveRC more accurate than an iCharger 3010?

I ask this because I have a pack that is showing 1's and 0's on my iCharger. Seems like the resolution of the reading is just not fine enough on these higher C packs.

Completely unprejudiced view from the maker of the meter (!!!) is that I cannot say as I don't know how accurate the iCharger is.
John Julian did a lot of comparative testing with the ESR meter, the iCharger and the PL8.
Generally the iCharger read slightly lower than the ESR meter whilst the PL8 read higher.
The advantage of the ESR meter is that it has a resolution of 0.04 milliohms whilst the iCharger only has a resolution of 1 milliohm.
This is a problem with large capacity cells where the IR can be close to 1 milliohm so trying to compare such cells is beyond the iCharger's capability.
In terms of absolute accuracy, the ESR meter will measure a resistor in Cell mode to within 1%

Wayne

I am curious becuase this afternoon, I did some Watt meter testing comparing 2 Gens Ace 5300mAh 6S packs. One 30C and one a new (not fully broken in) 60C.
I set up a 60 sized electric motor and ran it with a cheap Hobbyking P1 Wattmeter attached.

If I use the resting voltage of the pack-voltage under load
Then divide by the current draw during load
I get 31 milliohms for the 30C pack and 25 milliohms for the 60C pack (total IR of all cells).
I forgot to write down the iCharger values for the 30C but the 60C pack was showing up as 1's and 0's.

When starting with a resting voltage of 25.0V total, the 30C pack gave me 1581W after 5 seconds of full throttle while the 60C pack gave me 1669W. The 30C pack has more flights on it (about 20) and the 60C pack only has 3.
I was curious to track the IR during break in but don't think the iCharger has enough resolution for the task.

Progressive shows it's out of stock so I"ll order one when they come back in stock

Originally Posted by Melnic

I am curious becuase this afternoon, I did some Watt meter testing comparing 2 Gens Ace 5300mAh 6S packs. One 30C and one a new (not fully broken in) 60C.
I set up a 60 sized electric motor and ran it with a cheap Hobbyking P1 Wattmeter attached.

If I use the resting voltage of the pack-voltage under load
Then divide by the current draw during load
I get 31 milliohms for the 30C pack and 25 milliohms for the 60C pack (total IR of all cells).
I forgot to write down the iCharger values for the 30C but the 60C pack was showing up as 1's and 0's.

When starting with a resting voltage of 25.0V total, the 30C pack gave me 1581W after 5 seconds of full throttle while the 60C pack gave me 1669W. The 30C pack has more flights on it (about 20) and the 60C pack only has 3.
I was curious to track the IR during break in but don't think the iCharger has enough resolution for the task.

Progressive shows it's out of stock so I"ll order one when they come back in stock

It is difficult to measure IR by load testing because of the initial fall but measuring the two after a fixed time makes the COMPARISON valid if all other factors are constant ie connector values, temperatures etc. I have done a calculation suggesting that the total IR difference in your load testing is about 6.5 milliohms which ties up with your 25 and 31 totals. That could be just coincidence as there are so many variables.
I have measured 25C, 30C, 40C and 55C GensAce 2200 packs and found little difference in IR values. This was the cells and not the measurement techniques because full load discharge testing confirmed that the higher rated packs were no better.
I have not tested any 60C packs and will be interested to see the actual IR cell values.

ProgressiveRC should have stock early next week as I despatched a batch of meters to them last Tuesday.

Wayne

Well, the difference between the 30C pack and the 60C pack was about 5% and that was te difference in a similar test between a Nanotech 45C and 65C pack. I had done a side by side comparisson like this with the Nanotech and Gens and found the 6S 5000mAh 45C Nanotech was producing the same (within 1%) wattage on the watt meter as the Gens Ace 6S 5300mAh 30C pack. I'm thinking that Gens has bumped the C ratings to match the compeditors.

Originally Posted by Melnic

Well, the difference between the 30C pack and the 60C pack was about 5% and that was te difference in a similar test between a Nanotech 45C and 65C pack. I had done a side by side comparisson like this with the Nanotech and Gens and found the 6S 5000mAh 45C Nanotech was producing the same (within 1%) wattage on the watt meter as the Gens Ace 6S 5300mAh 30C pack. I'm thinking that Gens has bumped the C ratings to match the compeditors.

So we can say the Nanotech's are over rated.

For info. I have an iCharger 3010B. Mark Forsyth uses a 306B and I think also a a 106B. We got similar results from all 3 as far as I can tell.

As far as I can tell the iCharger uses the same 4 wire applied load technique as the ESR meter but a much lower current load (2A) and shows only 1mOhm resolution as noted. My observation was that the voltage signal during the discharge test appeared fairly noisy and this from memory was confirmed by a test made by LeszekJ on the iCharger thread. Possibly that's why the resolution is deliberately restricted - I don't know.

The PL8 technique has been stated as a brief 4 wire measured voltage change during charging but there remains some mystery about the exact algorithm since FMA have had to twice make changes to correct for an abnormally high cell IR when using; firstly main leads with unbalanced resistance, and secondly their multiple safe parallel board. All fixed now but it raises questions about whether it is true 4 wire as we normally understand it.

In any event the iChargers, the PL8 and the ESR meter give results that are fairly close and adequate for practical comparisons when batteries show consistently significant differences in IR. If using just one instrument accurate comparisons across batteries and cells should be excellent.

If you are serious about IR, then I think Wayne's meter is the obvious choice.

It approaches real life requirements much more closely than any other method short of actually doing a full load test, it is of much higher precision and each one is hand calibrated to high accuracy.

It's also very convenient and fast.

John

Originally Posted by Wayne Giles

Completely unprejudiced view from the maker of the meter (!!!) is that I cannot say as I don't know how accurate the iCharger is.
John Julian did a lot of comparative testing with the ESR meter, the iCharger and the PL8.
Generally the iCharger read slightly lower than the ESR meter whilst the PL8 read higher.
The advantage of the ESR meter is that it has a resolution of 0.04 milliohms whilst the iCharger only has a resolution of 1 milliohm.
This is a problem with large capacity cells where the IR can be close to 1 milliohm so trying to compare such cells is beyond the iCharger's capability.
In terms of absolute accuracy, the ESR meter will measure a resistor in Cell mode to within 1%

Wayne

WARNING this post contains the good AND the bad!

Good, Wayne, I am really enjoying your ESR meter. I recently purchased some "good" batteries and thanks to your meter, I was able to get some peace of mind by confirming lower IR values. It is also enlightning to see the IR change with a 5 and 10 degree (F) temperature change! Brings to mind the difference between "data" and "good data"

Ok, now for the bad. I just read the Banana Hobbies article where four different people tested some new "65C" batteries. First, way to go Wayne, JST connector on a 850mAh 65C battery, .85 X 65 = 55 amps which as Wayne points out is just SLIGHTLY above what they are rated for! How all the testers can conclude that these are honest 65C batteries is beyond me as there is no included data to support that claim. I believe that the four testers are all good people and talented modelers however that is not scientific proof of a rated discharge capability.

Finally, a question for Wayne, John, Charles et al.....
With regards to "IR", lipo's do not seem to scale well, that is for the same brand and "C" rating I have yet to see a smaller lipo that has the same low IR as a larger lipo. For example a 850mAh 65C brand X lipo will have a much higher measured IR than a 5000mAh 65C brand X lipo under the same conditions. Believing that IR is related to a batteries ability to discharge, would this not mean that a smaller lipo with the same construction and chemistry as its larger brother (or sister) by definition or reality can not have the same "C" rating?

Mind you, I have never tested the ability of the smaller lipo's sustained discharge however it just seems to me that.............

I understand that it is easy to have a family of "65C" lipo's in say 5 different sizes however, it seems to me that the manufactures are again missleading the consumers (intended or not). Of course, this would mean having to re-make their labels and perhaps creating even more confusion among lipo consumers

anyway, fireproof underwear on so, flame away!

Michael (if your not fryin, your not tryin!)

electryer,
Lower Capacity pas should have higher IR even at same C.
Punch in #'s into calculator
http://www.jj604.com/LiPoTool/

default 5millihom 5000mah pack was 15C.
change pack to 1000mah then keep changing IR till you get 15C again.

Originally Posted by Melnic

electryer,
Lower Capacity pas should have higher IR even at same C.
Punch in #'s into calculator
http://www.jj604.com/LiPoTool/

default 5millihom 5000mah pack was 15C.
change pack to 1000mah then keep changing IR till you get 15C again.

Yes, I think that is correct.
Remember that Mark Forsyth's original criterium for deciding whether a lipo is a good one is that the product of the capacity and the cell IR must be less than 12000.
This means that the IR must vary inversely with the capacity for the same cell makeup ie electrochemistry. If a 4000 mAh cell has an IR of 2 milliohms, then a 1000 mAh cell of the same type should have an IR of 2 x 4000/1000 = 8 milliohms. If you put these figures into the calculator it should give you the same "C" rating and FOM for the two cells.

Wayne

Originally Posted by Wayne Giles

Yes, I think that is correct.
Remember that Mark Forsyth's original criterium for deciding whether a lipo is a good one is that the product of the capacity and the cell IR must be less than 12000.
This means that the IR must vary inversely with the capacity for the same cell makeup ie electrochemistry. If a 4000 mAh cell has an IR of 2 milliohms, then a 1000 mAh cell of the same type should have an IR of 2 x 4000/1000 = 8 milliohms. If you put these figures into the calculator it should give you the same "C" rating and FOM for the two cells.

Wayne

Melnic and Wayne, thank you! Again, what sounded good to me, turned out to be comparing apples to oranges as the numbers do not lie! Lesson learned!

Michael

FYI,
Progressive has the ESR meters in stock.
Mine is on order

Got the ESR meter in today. It's late so I'll just post the measurements. Calculations I'll add later. These measurements are straight from the ESR.
I noticed one thing, when I add up the individual cell IRs, the total is significantly less than what the total pack IR is that the ESR meter mesures in pack mode. About a 5milliohm difference.

I will say that my packs use the 4mm bananna jacks and to use the meter, I used an adaptor that is very short. I fly the packs straight from the 4mm bananna jacks though. All these packs were in my Align 550FBL and I almost always keep it short enough to stay above 30% charge when I finish flying it.

All these were charged up with an iCharger 106B+ and it looks like it needs to have the cell voltages adjusted

Turnigy Nanotech 25C 2yrs old 30 flights (FOM .68, Max Current 92A, True C 18)
Pack voltage 24.92V
Cell voltage 4.15,4.15,4.17,4.19,4.20,4.22
total IR 25.2
Cell IR 3.52,3.20,3.28,3.44,3.40,3.36

Turnigy Nanotech 25C 2yrs old 30 flights (FOM .68, Max Current 92A, True C 18)
Pack voltage 24.96V
cell voltage 4.16,4.16,4.18,4.19,4.21,4.23
total IR 25.2
cell IR 3.52,3.16,3.28,3.32,3.52,3.40

Turnigy Nanotech 45C 1 month old 10 flights (FOM .88, Max Current 105A, True C 21)
Pack voltage 24.96V
Cell Voltage 4.16,4.16,4.18,4.20,4.21,4.23
Total IR 20.7
Cell IR 2.60,2.72,2.68,2.64,2.52,2.44

Turnigy Nanotech 65C 1 month old 10 flights (FOM .97, Max Current 110A, True C 22)
Pack voltage 25.04v
Cell voltage 4.17,4.17,4.19,4.21,4.22,4.24
Total IR 18.6
Cell IR 2.12,2.24,2.48,2.24,2.28,2.08

Gens Ace 30C 1 year old 15 flights (FOM .76, Max Current 104A, True C 20)
Pack voltage 25.0v
Cell voltage 4.17,4.17,4.19,4.21,4.22,4.24
Total IR 21.9
Cell IR 2.48,2.56,2.72,2.96,2.72,2.96

Gens Ace 60C 2 weeks old 8 flights (FOM 1.14, Max Current 127A, True C 24)
Pack voltage 25.0v
Cell voltage 4.17,4.17,4.19,4.21,4.22,4.23
Total IR 17.4
Cell IR 1.80,1.90,1.80,1.88,1.98,1.80

Melnic, that's telling you the resistance of your plug and leads is 5 mOhm. The ESR meter is quite precise and the difference is because Pack IR is exactly that - measured through the pack power leads.

In practice the Cell IR tells you about the individual cells in the pack and Pack IR tells you how the whole pack performs as seen by the power system.

Note this is different from some chargers where Pack IR is just a calculated sum of the cell IRs.

John

Originally Posted by Melnic

I noticed one thing, when I add up the individual cell IRs, the total is significantly less than what the total pack IR is that the ESR meter mesures in pack mode. About a 5milliohm difference.