Jason W M
Posts: 154
Score: 100
Joined: 3/26/2002
Last Login: 11/18/2011
From: Las Vegas,
NV, USA
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Unfortunately, many have seen this thread and its data and drawn the same conclusion that cork and others may have. Its clear to many Greg that you are in fact a firm supporter/representative of the Kokam product line through this forum and others, which is why some people might take your posting the wrong way. As a moderator however, I trust that you will always keep the interest of the entire online community at heart, only relaying facts and info you feel we should be aware of. I do know you will work hard to keep the forum open for the sharing of info as it was intended 
Id like to offer some food for thought and info some may find useful...
If in fact the TP 2100 cells did indeed perform as poorly as this graph depicts, surely someone out the thousands of people who have purchased these packs would have posted something, somewhere. Yet, I have never seen a single negative report or post regarding the performance of these packs on the Ezone, here on RCU or in any other forums.
BEC - I do want to say that Ive followed your work for MAN and others very closely over the years and I respect the work you have done for them and others immensely (You too Greg, Ive read a number of your articles as well! In fact, most of the products you reviewed I ran out and bought ASAP
Regarding the performance of your TP 2100s, even at 5-6C current draws, Im sure you have yet to see the poor run times as this graph does reflect. I wont argue with the voltage output under these loads however - the TP 2100s under a 5-6C load deliver about the same performance as my 8-9 cell KAN and HeCell packs, but of course at reduced weight and double the capacity. Still, by no means would I say this is poor performance - its much better than anything I have ever seen in their class!
As a note - the TP 2100 cells are NOT the primary cells in the Thunder Power product line. These cells were specifically designed as a low cost alternative to the superior TP 1950 and 2050 cells also available. And most importantly, they were designed to "fit" right in the place of the 2/3 sub A packs we have all grown so fond of in the past few years. But because they were produced to cost less and "fit" a specific physical dimension, some performance was sacrificed. However, the end result was well worth it since the packs are quite affordable, fit directly in place of 7-10 cell 2/3 Sub A packs most already use, and provide less weight with 2-4 times the capacity.
Keep in mind - for the reasons above the TP 2100 cells are NOT sold in 3p and 4p packs for sub C replacement. Due to their superior energy density (watthours per gram), the TP 1950 and 2050 cells are used instead. Fred does make reference to the 2100s being used in larger sub C replacment packs, but this is not true since they are not used for those applications. The energy density of these TP 1950 and new lightweight 2050 cells carry and energy density gravimetric in excess of 200 Wh/kg...still 30 Wh/kg more than the Kokam 1500 cells.
On a smaller scale, Ive recently tested a few Kokam cells versus Thunder Power myself and came up with some interesting results. The packs used were a Kokam 2s 340 and a TP 2s 730. Motor/gearbox is a GWS IPS-A drive spinning a 10x4.7 prop flying a T3D small 3D aerobatic indoor/parkflyer. This motor combo pulls around 2 amps static, fresh off the charger (Great Planes Triton - all charging is done as close to 1C as possible using .3 amps for the 340s and .7 amps for the 730s). Packs are 8.4 volts exactly off the charger using a Fluke DVM. The Kokam 2s 340 pack with lead weighs 21 grams, and the 2s TP 730 pack weighs in at 30 grams with the same amount of wire and lead (Deans 2 pin polarized). Tests results all come via an Astro Flight Micro Whattmeter.
The numbers for the Kokam 2s 340 pack:
2.05 amps, 8.01v, 16.4 watts output
TP 2s 730 packs:
2.03 amps, 8.00v, 16.2 wats outout
At first I thought the results looked very promising for the Kokam 2s 340 pack. It weighed less, yet had a tad more power output. However, it had 1/2 the capacity and only weighed 8 grams less so I was a little disappointed in the energy density overall.
I took both packs out for some back-to-back flying. For the first minute of flight, the airplane would hover and had a little bit extra reserve power for vertical climbout on the fresh 340 pack. The 730 pack had the same power but a tad slower climbout due to the slightly heavier weight. However, approaching the 5 minute mark, the 340 pack would now only hover the airplane. The TP 730 pack would in fact hover and still pull out vertically just a tad. I again checked the voltages under load to find the TP pack was still delivering over 7.8v but the Kokam was only outputting close to 7.4v. After 10 minutes of flying, the Kokam pack would no longer hover the airplane and was obviously near full discharge. I landed and found the voltage was around 7.2v (near fully discharged) - total flight time was just over 10 minutes, with an average current draw on the Kokam 340 pack to be around 6C (This airplane is flown mostly at full throttle since it is propped for thrust not speed and was flown on a breezy day - at only 5 ounces RTF it takes power to keep it flying).
After 10 minutes of flying, my TP 730 pack would still hover my T3D comfortably at full throttle. I took a short rest to cool the motor and then proceeded to fly another 10 minute flight on the already flown 730 pack. Total flight time was near 20 minutes, meaning average current draw was 3C.
I was fairly disappointed by the overall performance of the Kokam 340 cells in this application. By all indications, this application is very, very mild (6C avg) for a cell so heavily rated (up to 20C cont). I expected better voltage under load at reduced weight for better flight time. However, the TP pack weighed only 8 grams more with twice the capacity, providing a much better performing model overall.
When it comes to larger applications, I do in fact fly a number of TP 6150, 7800 and 8200 mah packs. I have had nothing but superior results using these packs in a number of various applications. On the note of voltage under load Scot, the 3p 6150 mah packs with 2050 cells actually put out the same voltage under 40-50 amp loads as the 4p 7800s using the 1950 cells. The 4p 8200 packs using 2050 cells deliver .2v per cell more voltage under load than the 7800s, which is a solid 1.4v more in a 7s pack. Youve seen the videos of my RappE flying with incredibly solid performance from the 6s4p 8200s...whose voltage under load is higher than my matched and zapped 20 cell 3000s.
I would however be very interested in seeing the related data of voltage under load for the new 1500 and 2000 mah cells. While delivering 80-90%+ capacity at 4-8C continuous draw is great, high voltage under those loads, and most importantly under 8-12C short terms bursts is most important to larger 3D heli and airplane pilots.
Is any such data currently available for the new Kokam cells?
Jason
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