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Old Jun 03, 2003, 10:10 AM
Burnin' holes in the sky!
SkyPyro's Avatar
Gilbert, AZ
Joined May 2003
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Kokam vs. E-tec

I have heard that E-tec LiPo cells are able to give out more amperage than Kokam cells at the same capacity. I was just wondering if this was true, and if so, how much more current are they able to dish out?
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Old Jun 03, 2003, 11:02 AM
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buzzsaw 46's Avatar
Spring Valley. MN
Joined Jun 2000
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No one really knows anything about the Kokam HD's yet as no test data has been released for over a month the only data we've seen was mistakenly posted and later deleted. But from what I've heard from someone who has tested the cells the data that was posted might have been accurate, I dont know this to be a fact as I have not seen a disscharge graph from this tester to compare to the one that was claimed to be inaccurate.

Bottom line is right now the E-techs are better by how much is just about anybodys guess. the only ones that know for sure are not saying.

I cant believe that there isnt any data yet, these new Kokams have been out for a month now the new Kan 1050's have been benchmarked already by two sources. They havent even been out a week yet have they?

Check out the extreme etech apps thread Here to see what people are doing with them.
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Old Jun 03, 2003, 08:18 PM
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Sacramento Metro, California, United States
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Try www.lightflightrc.com the have data for Kokam and E-Tech
on their web site.

Bill
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Old Jun 03, 2003, 08:57 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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I've posted this in other threads before. We cannot assume that all of a given manufacturer's cells perform the same. By this I mean in terms of the number of times capacity that can be pulled out of a cell. Some Kokams perform better and some worse than other Kokams. The same is true for E-Tec's. Each and every cell from a manufacture needs to be tested. Blanket statements that E-Tecs are better don't apply.

I've seen people post that E-Tec's are "wound" technology, while Kokam's are not. Again, that is simply not true. The Kokam 145's are wound, as I know someone who took one apart in a labratory environment. I've also seen posts that Kokam's are not high discharge. Again, this is not true. The Kokam 145's are high discharge. Blanket statements about all Kokam's should be avoided.

So, until the new "high discharge" Kokam's are available, we simply don't know. For now it seems that some E-Tec cells (the 250, 700, and 1200 in particular) perform very well at high discharges, and that is great. But, other sizes may or may not perform this well, and we won't know till they are available and someone tests them.

Not, to rant, but just to try and clarify.

Gordon
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Old Jun 03, 2003, 09:41 PM
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Walled Lake, MI, USA
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>> Blanket statements about all Kokam's should be avoided.

Gordon, thanks for your efforts to combat LiPo brand stereotyping. Blanket statements about any brand of LiPo should be avoided. If life were simple, we could just always buy the "green ones" and always avoid the "red ones." Life is rarely that simple. Depending on size and application, I could see myself buying LiPos from several different manufacturers, and believing that I had made the best decision on each one.
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Old Jun 03, 2003, 10:38 PM
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Skypro's post specified "at the same capacity".

Such evidence as we have seems to establish that the E-Techs do, in fact, put out more amperage than Kokams of the same rated capacity.

- RD
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Old Jun 03, 2003, 11:26 PM
Size Matters!
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San Francisco Bay Area
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Do a search for "Lipo Torture Test"
Draw your own results!
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Old Jun 04, 2003, 12:39 AM
DNA
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NE Ohio
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The specs are posted on the various web sites stating the C rate that the
cells can be used for. FMA shows 3C for the average rate for the older Kokam
cells and 5C for the average rate for the new Kokam HD cells. Aircraft World
posts the average C rate for Etec cells as being between 6 to 8 C. According
to many posts, these figures are fairly accurate. The cells can sustain higher
rates for shorter periods of time, or can be abused with resulting loss of capacity.
The Etec cells have been documented with user flying reports and graphs to
confirm the posted specs. The new Kokam HD cell's performance has yet to
be determined by several Ezone members actually using them. The loss of
capacity or retention of capacity when under a continuous load is the
determining factor between the two cells as well as their C rating. If one cell
can deliver 6C and retain 90% of its capacity, it would be better than another
cell that can deliver 6C but retain only 55% of its capacity.
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Old Jun 04, 2003, 02:17 AM
Former bpp dude
Joined Oct 2001
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I have tested the Kokams 1200HD's against the 1020's & E-tec 1200's. I will convert the data & post a graph as soon as I get a chance. Sorry for not being more active here lately, no time right now with two jobs, promise to be more active on testing new cells in the upcoming months when things get back to normal.

The short & skinny on the HD's are: A very nice improvement over the 1020's & they suffer from a little less voltage suppression than the E-tecs for the first several minutes at up to 6amps, then this voltage lead disappears & they are almost dead on in voltage. They do shut down long before the E-tecs are done though. I rate them smack in the middle of the Kokam 1020 & E-tec 1200. They can be very powerfull in a plane with proper throttle mangment. They are a very nice cell but not the next jump in battery tech. Thanks

-Troy
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Old Jun 04, 2003, 02:48 AM
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Spring Valley. MN
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Finaly the silence is broken

Thanks Troy for letting us know I'm sure there are many people who have been waiting to know for sure which packs are the best value. it seems the only place the Kokams would out perform the E-T's is a short duration pylon race, or in a highly aerobatic plane where duration wasnt a big issue. I guess the next logical ? is how much sooner did the HD's give up at 6A. we might have to wait for Troy's graph but given the voltage increase if the duration isnt to bad they might just have some applications where they could excell.
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Old Jun 04, 2003, 07:31 AM
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Walled Lake, MI, USA
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When it comes to evaluating LiPo performance, Troy has consistently been among the fairest and most credible in his conclusions. When I look at Troy's www.b-p-p.com site to evaluate LiPo cells for various applications, I see that one brand may have the lead in one area and another brand in another. For instance, it's well known that the E-Tec 1200 outperforms the older Kokam 1020 at higher current draws. On the other hand, the Kokam 1020 is lighter and less expensive. So you have to balance your true needs against your budget.

When I look at something in the 600-700mAh area, the 600mAh Kokam High Output packs clearly outperform the E-Tec 700mAh packs in just about every area but cost, according to Troy's numbers. In this case, the Kokams are more expensive because the High Output version actually consists of 145mAh cells in parallel. The Kokam 145s have been around a long time, and have proven themselves to be true high-performance cells.

For those who have a requirement for maximum performance, it is really important to fairly compare all of the options. To dismiss any brand as being incapable of having the best cell for a specific application accomplishes nothing but to limit your options. For those with less demanding applications and a tighter budget, there are less expensive options that will provide perfectly acceptable performance.

Troy is really good about focusing on the numbers -- performance, weight and price. That's why I like to use his test results and his website as a reference. The fact that Troy carries both E-Tec and Kokam cells tells me that he does not recommend one brand as being ideal for all applications.
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Old Jun 04, 2003, 07:47 AM
Size Matters!
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<When I look at something in the 600-700mAh area, the 600mAh Kokam High Output packs clearly outperform the E-Tec 700mAh packs in just about every area but cost,>

Dave, this can be very misleading, comparing built up 3s4p 145's w/ 3s 700cells. If you would compare (in flight & w/tach &wattmeter) the HD640 (kokams - the ones which received "all the hype" and newest generation) with the Etec 700cells in a 3s capacity you have a much more equal comparison and it would contradict your statement. In my opinion, the 700's out perform the 640 in every arena but weight. I would speculate that the newer 640 are not so new but may have the same technology/construction as the older 145's in larger capacity. Either way they are a huge step above the previous 1020's which I don't even bother charging anymore!
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Old Jun 04, 2003, 09:23 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Troy,
Thanks for the sneak peak at your results.

Quote:
Such evidence as we have seems to establish that the E-Techs do, in fact, put out more amperage than Kokams of the same rated capacity.
RD,
For what it is worth, E-Tec makes a 130mAh cell. This is not exactly the same capacity or weight as the Kokam 145 (sometimes called a 135 or 140), but it is close. The E-Tec 130 in my testing and usage is not as high as discharge as the Kokam. In this case the higher discharge capable cell of equivalent size is the Kokam. However, I've only had the ET-130's less than two weeks and was working 15-hour days, so haven't had time to do much more with them yet. I reiterate, not all E-Tec's or Kokam's are the same. They have to be checked.

Gordon
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Old Jun 04, 2003, 11:22 AM
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Walled Lake, MI, USA
Joined Feb 2000
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RocketBob, the only "fair" evaluation for a customer is performance, weight and price. I could care less what combination of cells is under the shrink wrap of the pack, or which brand name is stamped on the outside. All I care about is how it performs, how much it weighs and how much it costs.

If you're trying to prove that cells of one brand are always better than cells of a different brand, I can see where you would say that it's not fair to compare a pack of parallel smaller cells of one brand against larger cells of another brand that are not in parallel. That's fine if you want to debate that point with people who are looking to debate such things.

I'm not interested in proving that one brand is always superior or always inferior to another brand. I look at my application, compare the available options in terms of performance, weight and price, and select the package that best fits my needs.

I can see several different applications where the B-P-P parallel 145 packs offer the best performance and lowest weight when compared against any other available options regardless of brand. You simply have to decide if you are willing to pay a premium price for this.
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Old Jun 04, 2003, 01:28 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
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RocketBob,
It would seem "fair" to compare apples to apples, and items costing the same as like "items". After all, "like" items should cost about the same and if they don't, somebody is trying to get rich. In the case being "discussed", the kokam 600 costing $40 is not in the same league as the ETec 700 at $22. Sure the Kokam is better, but for twice the price, it should be.
hoppy
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