Posts: 180
Joined: 8/5/2003 From: Frederick, MD, USA Status: offline
The data attached is the first realistic test data for life cycle seen in any of the forums. Nathan Gwozdecki ran life cycle tests on the popular FMA Direct CP 2000 HDR pack in 3S configuration.
Salient observations:
1. All done under carefully controlled lab conditions using precision test equipment. 2. The data is very conservative with the cells not cooled during charge or discharge but cooled by fan after discharge and before charge as one should do in the field. Any cooling in the airplane would extend life. 3. All runs were at a constant 17.5 amps discharge reflecting the average current drain for many applications in helicopters and with the many new brushless motors that draw some 15 to 25 amps and are replacements for Speed 400 brushed motors. Discharge was cut off at 3V/cell based on individual cell voltage. cell voltage characteristically rebounds to the neighborhood of 3.65 to 3.8 V when load is removed and the cell cools a bit. This amounts to about a 5% rebound of capacity. 4. All charges were done at 3C to 94% (1785 mAh) to expedite time. Even so, the tests took almost 14 solid days. 5. The test pack is a 3S CellPro pack with tap and connector so that cell voltage could be recorded ala CellPro. 6. Handling and plugging/unplugging of the pack was minimized. 7. Cycle life as defined by international standard 80% of base capacity was 450 cycles. The pack was run to complete death just to see what would happen. Results are interesting: Capacity declined slowly and steadily to 475 cycles, then plummeted. Dissassembly of cells confirms the rapid formation of salts (dendrites) as the cell dies. 8. The peak temperature rise for eacy cycle is recorded and averaged 65 Deg F over the life of the pack. It is interesting that, as cell capacity falls gradually and run time shortens very sligtly, rise temperature falls very slightly as well. Since discharge current was always a constant 17.5 amps, this implies that internal resistance was not degraded and, if anything, increased only slightly. The data recorded by Rod shows that the TP 2100 runs 161.5 Deg F at the 17.5 amp discharge , so it will be history very shortly as test runs begin. 9. The need for and achievement of cell balnce is also graphed. Cell voltage was brought to wihthin plus and minus 5 millivolts even after 450 runs. This is a powerful statement of the desirability of cell balancing as done by FMA BalancePro systems. 10. The discharge profile matches the flight profile for a typical trex heli or any of the new generation of brushless motor propulsion systems that demand an average 200 watts. 11. Life cycle cost for a stock CP 2000 3S pack is $83.50/450= $0.18/flight compared to $1.41 per flight per the 60 cycles for a TP 2100 that RC Tester and trex report. Nathan will validate that figure very soon as it won't take long to run 60 cycles. 12. Test of the TP 2100 Prolite 3 has been completed and the pack lasted 38 cycles when tested under the exact same conditions as the KOK 2000. The attachment has been revised to show that data.
TP proponents averred that the TP results were influenced by charging the TP pack at 3C as described above. The tests were repeated with charging done at 1C. To be certain that both cells were tested head-to-head, a CP 2000 cell and a TP 2100 Prolite 3 were wired in series to form one pack so both cells saw precisely the same conditions. The results in the attachment show the TP 2100 going below 80% capacity at 85 cycles. And this is at a 10C discharge rate.
In a separate, independent test the data in the following thread showed loss of 5.5% capacity in ten cycles at 15C on the TP 2100 cells. 20% loss/0.55 % per cycle = 38 cycles.
Posts: 180
Joined: 8/5/2003 From: Frederick, MD, USA Status: offline
This is a point in a progression. Our Li Pos (and we suspect most Li Pos) maintain life cycle as long as cell temp is held below 140 deg F. We also know that life cycle at 185 Deg F is one cycle, i.e., the cell is ruined. Now, we need at least one or two points that define the cycle life Vs temp line. As it turns out, 17.5 amps for the CP 2000/15C generates cell temp of 133 deg F. Other points will be done at higher temp to see what cycle life is. This test also was designed to see the impact of charging at 3C since folks were asking that question. It also happens that the 17.5Amps = 9C is a good data point because that is the average point for a large number of current helicopter and airplane propulsion packages. New data will be posted as it is generated.
< Message edited by Fred Marks -- 4/20/2006 5:57:11 PM >
Posts: 823
Joined: 12/30/2001 From: AUBURN, GA, USA Status: online
Fred Great work. It really show's how the temp of batteries affect the life cycles of lipo batteries. I am by no means a electron genus but had contact last year with a couple Lipo manufacture who had told me if you try to manufacture lipo's with a high discharge and try to keep them light they will have a short life if run at a high discharge rate. Posted this on a group about a year and half ago and was told I was nut's when I said you would cut the life cycle down to about 50 cycles. So that other's and myself can understand what is the weight difference between the Kokam and TP battery, The point that I am trying to make is that lighter is not all way's better. Even a lot of the lower cost 12C rate batteries that are on the market hold up better than the lighter 15C rate batteries because they are a little heaver and keep a lower temp under load. Ever tried to put 1 1/2 gallon's of water in a gallon jug.
Milton
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Posts: 180
Joined: 8/5/2003 From: Frederick, MD, USA Status: offline
quote:
ORIGINAL: Milton
Fred Great work. It really show's how the temp of batteries affect the life cycles of lipo batteries. I am by no means a electron genus but had contact last year with a couple Lipo manufacture who had told me if you try to manufacture lipo's with a high discharge and try to keep them light they will have a short life if run at a high discharge rate. Posted this on a group about a year and half ago and was told I was nut's when I said you would cut the life cycle down to about 50 cycles. So that other's and myself can understand what is the weight difference between the FMA CP and TP battery, The point that I am trying to make is that lighter is not all way's better. Even a lot of the lower cost 12C rate batteries that are on the market hold up better than the lighter 15C rate batteries because they are a little heaver and keep a lower temp under load. Ever tried to put 1 1/2 gallon's of water in a gallon jug.
Milton:
Per the measurements of actual production packs by R-C Tester reported in his thread:
a 2S1P pack of TP 2100 weighs 95 grams and a like pack of CP 2000 weighs 120 grams or 25 grams more. The impact of lighter weight is shown with dramatic clarity in the initial post of this thread. Even the most avid boosters of TP cells can not deny that a 10:1 difference in life cycle occurs when tested exactly the same way, head - to- head. We are not saying that lightweight cells are bad. Rather, the point is that they must be marketed and used properly to be cost effective. If you operate that TP pack in such a way to keep the temperature below 140 Deg F, cycle life will be better. That means keeping average current draw to less than 8 amps. The issue is that the purveyor of that cell keeps trying to convince people that it will withstand 12C; 15C; 20C or more (depending on the "hype of the day" and stay at a safe temperature. The R-C Tester thread clearly shows how bogus those claims are. Fact: with the powerful brushless motors used , e.g. in trex helis, drawing 17 to 25 amps in the major RC applications that used to draw 10 amps from Speed 400 geared motors, the 1 ounce difference in pack weight simply gets lost. The only proponents of the super lightweight cells operate small park flyer models with mostly brushed motors that can not tolerate more than about 12 amps max and the lightweight cells contribute there. They just do not make sense in bigger airplanes in which one has to parallel so many that the weight is equivelant to the higher weight, long life cells and the cost is much higher.
< Message edited by Fred Marks -- 4/20/2006 6:00:06 PM >
Posts: 43
Joined: 9/17/2003 From: WHEATON,
MD, USA Status: offline
My two cents worth.
My Thunder Power packs have been treated with extreme TLC since first purchased. Their performance and longevity has been dissapointing to say the least. I have taken the task of making everyone aware of my "experiences" in this regard.
I have been charging all my Lithium Polymer packs at .7C and discharging at less than 70% of their safe specified "discharge rate". I has made no difference, both failed Thunder Power packs refuse to take a charge after approximately 50 cycles (?). Contacting them via e-mail to find a way to resolve this issue was irritating at best. To begin with I have a strong dislike for reading replies typed using UPPER CASE typeface through the entire reply. Calling them on the phone was not that much better than reading their replies. I have written all my T/P packs off as a total waste of money, and I am no longer a happy camper when I take that step.
Had I known this before investing my money on this particular manufacturer's products, I would have never bought as many of them as I have. I am afraid I have been hoodwinked into believing that I was getting a product with reliable superiority and longevity based on the Made In The U.S.A. legend printed on their packs. I guess I was wrong.
Funny thing is that the Kokams I own, packs which are much older than the T/Ps all are still performing as good as the first time I used them. For the time being I will stick with Kokam packs. I don't care if my model is a few grams heavier than with other make of Li-Pos, or if I have to make the battery compartment a bit larger for them to fit in properly.
I'd rather put up with so doing and be assured that I am using a reliable product, one that will deliver not only performance but longevity in the long run as well.
< Message edited by qban_flyer -- 1/23/2006 2:58:33 AM >
Posts: 180
Joined: 8/5/2003 From: Frederick, MD, USA Status: offline
quote:
ORIGINAL: Fred Marks
This is a point in a progression. Our Li Pos (and we suspect most Li Pos) maintain life cycle as long as cell temp is held below 130 deg F. We also know that life cycle at 185 Deg F is one cycle, i.e., the cell is ruined. Now, we need at least one or two points that define the cycle life Vs temp line. As it turns out, 17.5 amps for the KOK 2000/15C generates cell temp of 133 deg F. Other points will be done at higher temp to see what cycle life is. This test also was designed to see the impact of charging at 3C since folks were asking that question. It also happens that the 17.5Amps = 9C is a good data point because that is the average point for a large number of current helicopter and airplane propulsion packages. New data will be posted as it is generated.
THE FOLLOWING QUOTE IS OF INTEREST:
[quote=NotAnAceYet;41469]I've got 2 Tanic 3s 1550's that are about a year old. I've been using them with a Himax 2812-850 Outrunner and a 10x4.7 APC prop - maximum amps at WOT 12.5 amps.
All of a sudden, both batteries are experiencing the same symptom - charge OK - balancing with the taps ok - show a full charge on wattmeter, but when I power up they only deliver the 12 amps for 20-30 seconds then drop off to 7-8 amps and slowly decline from there.
I bought both of these at the same time.
I do have 2 newer Tanics that work fine, as does a Hyperion 1450 - so I've pretty much ruled out the motor and speed control.
Does it sound like the batteries are finished? These were my first 2 lipos I purchased, so I have no experience with "end of life" symptoms.
I'm afraid you are getting some now. Sorry. ( BY RED SCHOLEFIELD)
Not an ACE Yet:
You can contribute to the information base if you will please. Do you have an estimate of the number of cycles on the pack? Kevin Thomas has been kind enough to tabulate all the data in the RCU thread that posts the data many people have taken with the CBA. The attached is an anagram built from that raw data that allows the reader to see in an instant what is going on. the TANIC 1550 has not been added to the file, but the TANIC 1750 is. The cells are similar. it would be a reasonable estimate that the inner cells in your pack run at above 140 F if you are running the power you state. You can check the life cycle one might get.
Posts: 392
Joined: 3/20/2002 From: denver,
CO, USA Status: offline
I have several 3cell 2100 TP that are over 2 years old, that do not get babied. My guess is over 200+ each cycles so far. when done flying they are less than 100-110F when checked just after flight. I have over 12 lipos ranging fom 1300 to 8000 mah, from being 2+years to 1 month new and the only time one goes bad is
1: overheated in metal trailer while being stored 2: frozen in 20F temp overnight. 3: left plugged in and discharged to 2.1v 4: lawn darted in the ground from 200ft up and the motor mount bolt inserting itself into the battery(did not flame up only puffed and got very hot 160F) ALL OF THE ABOVE I HAVE DONE. EXPENSIVE LESSON LEARNED.
They show no signs of going bad at this time. they get heavy use and charged at 0.5C max.
these are the yellow strip version gen2 and a few gen 4.
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FMA Li Po Pack Life of 452 Cycles at Heavy RC Discharg... - 
and stay at a safe temperature. The R-C Tester thread clearly shows how bogus those claims are. Fact: with the powerful brushless motors used , e.g. in trex helis, drawing 17 to 25 amps in the major RC applications that used to draw 10 amps from Speed 400 geared motors, the 1 ounce difference in pack weight simply gets lost. The only proponents of the super lightweight cells operate small park flyer models with mostly brushed motors that can not tolerate more than about 12 amps max and the lightweight cells contribute there. They just do not make sense in bigger airplanes in which one has to parallel so many that the weight is equivelant to the higher weight, long life cells and the cost is much higher. 
RE: FMA Li Po Pack Life of 452 Cycles at Heavy RC Dis... -