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  1. #1
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    The following statements and data come courtesy of Fred Marks, CEO of FMA Direct.

    The attached data has taken some time and the help from many to generate. It is a powerful set of data. I am happy to credit each of the following. In particular:

    1. Don Srull who started the testing back in Feb before he had to have a bit of time to take care of his health. Don's purchase and test of the Thunder Power 2.1AH cell has added immeasurably to the data in hand.

    2. To Red Scholefield who has put in many hours testing all the Kokam cells in the series drawn randomly from inventory stocked in by Kokam USA.

    3. To Troy Goff of B-P-P who generously posted the data in the form of discharge time vs voltage that permitted the E-TEC 1200 cells to be included.

    4. To Jamie, Greg, and JJ for critique of the methods and findings.

    5. To Red, Don, Tim, JJ Hong, and Greg who critiqued the presentation method.

    6. To JJ Hong and the staff at Kokam for the discharge curves in the specs. We are very happy to see that the data recorded independently by Red and Don correlates almost exactly with the Kokam data. I think this objectivity will be obvious to the reasonable reader of forums on the internet. Our new speed controls allow the cut-off to be programmed at an optimum 2.8V and most brushless controllers afford the same. Most ESCs have a 5.3 V cut-off that will be fine for 2S packs.

    The observations from study of the data in the attachment are as follows:

    1. These are all 1S cells or packs, not in parallel packs. As cells are paralleled, the capacity and discharge current available multiply by the number of parallel cells. This makes these tests truly apples and apples. For example, a 4S3P pack of KOK 1500s will be able to handle most heli and similar applications with 12 cells instead of 16 2100s. The savings in weight will permit the aircraft to fly at lower throttle settings and, thus, as long as the larger, more expensive pack of 2100s.

    2. You can judge the relative performance from review of the curves.

    3. The KOK 1500 and 1900 (2AH) mah cells operate satisfactorily to 10C with proper throttle management and will be specified that way. Both cells have continuous capability without excessive heating (About 50 Deg C) up to 8C. Beyond 8C, a realistic duty cycle of 5:1 at below 8C and at above 8C respectively will be specified.

    4. The KOK 340HSC is phenomenal with loss of just 12% capacity at up to 20C.
    Although a bit pricey, Troy has seen great response to a KOK 340HSC "Square Sub - C cell" that is made up into a 4P pack that is 1.32 AH and can deliver up to 26.4 amps.
    Out to 6.8 amps, the 240HSC keeps pace with the larger cells and beats the 1200 badly.

    5. The KOK 700HD is not quite as stiff as the other three Kokam HD cells but still loses only to 43% capacity at 10C. This performance is about that of the 1200 shown.

    6. Do remember that these curves are non-dimensional with regard to run time that rises with cell capacity due simply to having a larger (Thus heavier) cell and with paralleling.
    **************************************************

    We want to say thanks to all who helped generate this objective data obtained independently of either Kokam Eng Ltd, Co or Kokam USA. We think the decision to make Li Po a "Battery System" with all the things you need to be successful is a good approach. It lets one build a custom pack and size it for the aircraft of the moment. We are truly impressed that Greg Covey flew four different and diverse airplanes in one afternoon using the connector boards and the same packs of cells to form up different pack configurations. For those who want a big, fixed pack, we will be coming on with those very soon.

    Regards,

    Fred Marks
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  2. #2
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    PERFORMANCE COMPARISON FOR LI PO CELLS
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  3. #3
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    EFFECT OF CURRENT DRAW ON CELL CAPACITY AS A MULTIPLE OF CAPACITY, C
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  4. #4

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    Kokam USA / FMA Direct Cell Comparisons

    Greg, the TP2100 result don't seem to be inline with what people are seeing in the field (more precisely, what I read about as I have never tested them). They were also from Feb, which is quite old technology for lipo these days - any chance of someone qualified testing the current TP2100 packs?

    Stu.
    Stu Maxwell - StumaxAircraft

  5. #5
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Stu,

    I'll think you'll find that Red Scholefield is more than qualified. Additionally, these were new TP packs that were tested.

    Regards.
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  6. #6

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    Kokam USA / FMA Direct Cell Comparisons

    Greg, assume you sell Kokam cells. What is your store name?
    Do you have $ list?

  7. #7
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    No, I don't sell any products. The above information was provided by FMA Direct. You can buy Kokam cells or packs there.
    Visit my Web Hangar at www.gregcovey.com/rc.htm

  8. #8

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    Kokam USA / FMA Direct Cell Comparisons

    Greg, I agree, Red's up to it, but the cells tested are not the same as the ones you can get now. I'd just like to know how they compare. Some of the guys at rcgroups are getting better results than the graph would suggest, and before I spend that much on either brand, I'd like to know what I'm getting.

    Stu.
    Stu Maxwell - StumaxAircraft

  9. #9
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Stu,

    I wasn't aware of the cell difference but, in general, you will see a bell-shaped curve on any of these Lithium cells from lot to lot. Perhaps this is what folks are seeing.

    Good luck getting any curves from ThunderPower.
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  10. #10

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    1500HD specs?

    Anyone know the weight and dimensions of the 1500HD cell? FMA website lists these as TBA, but I'd rather know now, for planning purposes. Thanks for any help.
    Marcus

  11. #11

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    Kokam USA / FMA Direct Cell Comparisons

    Greg, maybe Don got some bad cells to test - I just can't see them performing as badly as these graphs would have us believe. BTW, I have no affiliation with TP (or any cell mfg) and the only lipo cells I've used so far are the Kokam 3270's and Etec 1200's, both of which work well if used within their design limits.

    These graphs would imply that the Kokam 2000 cell is one of the best - but it doesn't seem to be available. I am looking for a power source for an EDF using a Hacker B4019L - I need 9S lipos that can handle bursts of 18-20A, then cruising at 12A. I was originally thinking of TP2100 as a 9S1P pack, which would be OK according to flight tests I've read about from other people. The Kokam2000 cells appear to be better from the above tests but how do I get some? I will also need in the near future, 10SxP capable of sustained 50A with 80A bursts, and next year 80A continuous and 100A bursts (aiming for 3kW for EDF). My company has several high end EDF projects underway which will need the best cells available. As a manufacturer I need to be able to specify the best possible combination for my kits (and my own fan/motor combo when it's ready) - it gets hard when you see conflicting information from various sources and the cost of purchasing all the cells to compare them yourself is beyond reality (I hope the various cell manufacturers are listening and want to help my product development). I could buy one cell and test it, but we all know that won't tell me how it will perform with 8 or 9 other cells in a pack in a plane in the air. I hope you guys can understand my dilemma.
    Stu Maxwell - StumaxAircraft

  12. #12

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    Kokam USA / FMA Direct Cell Comparisons

    I don't get here very often as I spend most of my internet time (TOO MUCH ) on R/C Groups/AKA the Ezone. But a link from a thread over there to this one got me here...

    Anyway, the curves, especially the one showing performance as a function of "C" discharge rates square up with those cells that I have experience with (am eagerly awaiting weights, dimensions, prices on the new Kokam 1500s). These include E-Tec 1200s and Thunderpower 2100s (as well as Kokam 1020s, 640s and 1200s).

    I have been a little disappointed in my TP2100s (I've gotten one 2s pack from BPP and one from Esprit Model). I was expecting them to hold voltage better than they do at greater than 5C discharges. That said, in the airplanes I'm using them in they are away better than the 8 cell KAN 950s they replace, mainly because the weight decrease (over three ounces) offsets the performance decrease. And, I'm running them at 12A tops. Further, I liked the one well enough anyway that I bought a second one, and I will be using them as much as I can.

    I've seen lots of enthusiastic posts on R/C Groups about 3s packs of TP2100s in planes that used to have 8-packs of KAN 950s or HECell 1100s and I can see why that might be..... but I also think that using TP2100s at 15A draw makes about as much sense as using HECell 1100s at that current - which is not alot. Both of them are overtaxed at those currents.

    I wonder if Fred's going to have any 1500s at the NEAT Fair? :idea:

  13. #13
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    Kokam USA / FMA Direct Cell Comparisons

    I have used many different cells and i have got to say the Kokham 340 cells are amazing.

    Stumax, if you want lightweight and 100a you have got to go to a multiple pack of 340s Bishop power have just made me a 8s10p pack of 340s (3400ma) that can give 70a continuous and over 100 in bursts.

    if you look at the chart that shows the capacity under load you can see the 340 outperforms all other cells (in my pack config. it even outperforms the Ni Cads as far as volt drop is concerned)

    Dave

  14. #14
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Bernard,

    Welcome to the Electric Aircraft Universe.

    For our readers that don't know you, Bernard E. Cawley (or BEC) is one of the most reputable names in electric flight power systems.

    Yes, FMA Direct will have both 1500HD packs and cells at the NEAT Fair. Stop by and check out my Graupner ShowFlyer that uses two 4s5p packs of 1500HD cells. The sustained power output level is simply amazing.

    I also look forward to meeting you!

    Regards.

    Dave,

    Your pack of 8s10p 340 cells is certaintly impressive! Keep in mind that for many applications, it is not the most cost effective approach. In general, the larger capacity cells are less expensive because you need less of them.

    My 4s5p pack of Kokam 1500HD cells can deliver 60amps continuous with a 7.5AH capacity in only 20cells vs. your 80 cells. It's an "apples to oranges" comparison, but you get the idea.

    My point is that your pack may be best suited for an HLG application and mine for a 3D flyer.

    Regards.

    Marcus,

    I can't seem to find my data sheet on the 1500HD cell for the dimensions but the weight is 32 grams.
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  15. #15
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    Kokam USA / FMA Direct Cell Comparisons

    Hi Greg,

    the Battery i have made up is for a 2m x2m F3A pattern/3D plane specifically for an Artistic Aero Competition (British Freestyle Champs) the idea is to have maximum performance with minimal weight and just last the 4 minute flight.

    I agree with the larger cells less of them theory and i will use many different packs in this plane, its just i wanted the ultimate performance from this set up to prove to people just what can be done.

    the main plus for these cells is that they maintain their voltage under load better than nicads.

    Dave

  16. #16
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Dave,

    I figured that you had an application along those lines.

    In your case, you made the best choice.

    Let us know how your British Freestyle Championship goes!

    Regards.
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  17. #17

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    Kokam USA / FMA Direct Cell Comparisons

    Originally posted by Greg Covey

    For our readers that don't know you, Bernard E. Cawley (or BEC) is one of the most reputable names in electric flight power systems.

    Yes, FMA Direct will have both 1500HD packs and cells at the NEAT Fair. Stop by and check out my Graupner ShowFlyer that uses two 4s5p packs of 1500HD cells. The sustained power output level is simply amazing.

    I also look forward to meeting you!
    Yikes! Do you have a smiley for red-faced embarassment?

    I'll have to see about trying a 1500 pack or two......

    Since you seem to have some of these cells already - how big are they and what do they weigh? Last time I looked at the FMA site (yesterday) they showed TBD/TBD. Would love to try some, perhaps in the Switchback Sport RG that I've been flying on the TP 2100s, but I would like to know before buying them if they will fit.

  18. #18
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Bernard,

    The weight of the 1500HD cell is 32 grams. I can't seem to find my data sheet on them and I'm not sure why FMA hasn't posted the dimension specs. They aren't much bigger than the 1200HC cells. Perhaps a little taller.

    The big (or huge) shipment from Korea was delayed a bit, otherwise they would be for sale already. I would expect Hobby Lobby and Bishop Power Products to be picking them up as soon as they arrive.

    I'l continue to look for my data sheet...

    Regards.
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    Spec sheet for 1500

    Originally posted by Greg Covey
    Bernard,

    The weight of the 1500HD cell is 32 grams. I can't seem to find my data sheet on them and I'm not sure why FMA hasn't posted the dimension specs. They aren't much bigger than the 1200HC cells. Perhaps a little taller.

    The big (or huge) shipment from Korea was delayed a bit, otherwise they would be for sale already. I would expect Hobby Lobby and Bishop Power Products to be picking them up as soon as they arrive.

    I'l continue to look for my data sheet...

    Regards.
    I've got it in pdf format, e-mail me back channel and I'll send it.

    Here is a clip from it that might answer some questions.

    1 Nominal Capacity*1 TYP.1500mAh
    2 Nominal Voltage 3.7 V Max. Current 1.0CmA(1450mA)
    3 Charge Condition Voltage 4.2 กพ 0.03V Cut-off Voltage 3.0 V
    5 AC Impedance (mOHM) MAX. 32 AT 1KHz Charge 0OC ~ 45OC
    6 Operating Temperature Discharge -20OC ~ 60OC
    7 Weight(Approx.g) 32.5 Volumetric 348 Wh/คำ
    8 Energy Density Gravimetric 171 Wh/kg

  20. #20
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Here are the dimensions of the Kokam 1500HD cell...compliments of Red.
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  21. #21

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    Kokam USA / FMA Direct Cell Comparisons

    Got it - Thanks!!

  22. #22

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    Kokam USA / FMA Direct Cell Comparisons

    I find it hard to believe that no one finds it a bit fishy that the company
    (as kokam is a division of FMA as far as kokam cells say on the label anyway)
    doing the testing just happens to be the same company
    that comes out top on the tests?. i also find it kind of weird that
    it only seems to be this test that finds the TP's so lacking?
    after all Jason Shulman was ONLY able to finish in seventh place at the
    F3A World Championships flying Thunder Power packs.

    phil

  23. #23
    Moderator Greg Covey's Avatar
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    Kokam USA / FMA Direct Cell Comparisons

    Phil,

    You are mistaken. Just because one Lithium cell outperforms another doesn't mean it is "lacking". When you parallel enough of them, many cells can perform the way you want them to.

    In general, any Lithium cell outperforms NiCd technology.

    Don't be so suspicious, buy some of each pack and test them yourself. We would love to see additional sources and results.

    Regards.
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  24. #24

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    Kokam USA / FMA Direct Cell Comparisons

    Originally posted by Greg Covey
    Here are the dimensions of the Kokam 1500HD cell...compliments of Red.
    Hi Greg,

    This is perfect. Thanks! Do you (or Red, Fred, JJ?) have one of these drawings for the 2000HD you can post?

    Thanks,

    Daren

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    Kokam USA / FMA Direct Cell Comparisons

    Here's another comparison chart from FMA site:

    https://www.fmadirect.com/site/Detai...726&section=28

    I had no idea that running my KR600AE packs at 10A in a S400 pylon racer, I only have 20% capacity (ie, 120mAh!) and ~1min run time! Or take a look at the Sanyo HR-4/5AUP curve, and compare to Sanyo's own data:

    http://www.flydma.com/batteries/specs/1700Ni.pdf
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