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Li- Poly - 7/19/2003 7:36:43 PM   
tailheavy



Posts: 132
Joined: 5/12/2003
From: Virginia Beach, VA, USA
Status: offline 		How about 3c1p E-tech 1200 on a GWS 300c-C gearing? Would that be OK with a 10x4.7 prop?

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       Post #: 26

Li- Poly - 7/20/2003 3:15:08 AM   
drksyd



Posts: 578
Joined: 5/25/2003
From: Honolulu, HI, USA
Status: offline 		That would be close, you might not want to hold it full throttle too long. You should be fine with the 3S and 9x7 prop. Nominal voltage for the 3S is 10.8, actual charge voltage up to 12.6 volts, much higher than a 8 cell nicad/nimh which is the highest suggested amount of cells to fly with.
In KenSP's thread of his EStarter with floats, his plane looks pretty strong and powered only by a 2S with timed motor so that's another method to increase power for free.

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       Post #: 27

Li- Poly - 7/20/2003 3:33:51 AM   
tailheavy



Posts: 132
Joined: 5/12/2003
From: Virginia Beach, VA, USA
Status: offline 		True. My motor is untimed right now. I am waiting on the batteries to get here.

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       Post #: 28

Li- Poly - 7/20/2003 4:01:57 AM   
drksyd



Posts: 578
Joined: 5/25/2003
From: Honolulu, HI, USA
Status: offline 		I looked at the motors and not sure how you time it. I know you turn the endbell clockwise(?) but it doesn't look like you can turn it without damaging it. The car motors had screws to hold the endbell, these don't.

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       Post #: 29

LiPo safety - 7/28/2003 8:35:13 AM   
Manga


 

Posts: 8
Joined: 7/28/2003
From: Melbourne, FL,
Status: offline 		I am new to this type of battery, but it seems that either overcharging or completely discharging them are the most common problems. Is there a charger that will effectively prevent overcharging? and Is there an onboard device that will prevent discharging the batteries below the safety zone?

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       Post #: 30

Li- Poly - 7/28/2003 10:45:41 PM   
tailheavy



Posts: 132
Joined: 5/12/2003
From: Virginia Beach, VA, USA
Status: offline 		I couldn't get the e-techs so I got the kokam 1200 high capacity 3 cells instead. I already re-timed the motor since putting on this pack and wow, talk about a difference in power. There was no need to even go to full throttle with this set up. I can basically shoot out of a hover no problem on my fan fold ultimate bipe. How do you measure the current with an amp meter. I tried hooking the amp meter in series with the battery but the esc cuts out real quickly. It runs fine without going through the meter. Maybe I'm supposed to hook it up in series with the motor instead? Yea that's the ticket.

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       Post #: 31

Li- Poly - 7/28/2003 11:26:36 PM   
drksyd



Posts: 578
Joined: 5/25/2003
From: Honolulu, HI, USA
Status: offline 		Did the Kokams just hit the market? Last time I looked they still weren't available. What kind of amp draw can they handle?

Manga
There are chargers designed specifically for lithium packs and I would suggest getting one if you do get lithiums. It's failsafe and you won't regret it.

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       Post #: 32

Li- Poly - 7/31/2003 7:44:57 AM   
JJ HONG


 

Posts: 44
Joined: 7/14/2003
From: SEOUL, KOREA, REPUBLIC OF (KOR)
Status: offline 		[QUOTE]Originally posted by drksyd
Did the Kokams just hit the market? Last time I looked they still weren't available. What kind of amp draw can they handle?

Manga
There are chargers designed specifically for lithium packs and I would suggest getting one if you do get lithiums. It's failsafe and you won't regret it. [/QUOTE]
--------------------------------------------------
new kokam 1500HD cell handle 9Amp constant and 15Amp burst for 10 sec.kokam 12ooHD /6Amp draw constant,9A burst.

I also recommend to use lithium special charger like kokam lipo-402 or TRITON or equivalent lithium chargers which have constant current -constant voltage controllerable argorism to get full charging.only constant current charging will give only 60-70% charging and may cause fire due to the overvoltage charging.

(in reply to Aero330LX)
       Post #: 33

Li- Poly - 7/31/2003 6:31:03 PM   
tailheavy



Posts: 132
Joined: 5/12/2003
From: Virginia Beach, VA, USA
Status: offline 		Not sure where you got that info from but the data sheet that came with my new kokam 1200HC said that it can handle 8C average maximum current. That works out to be 9.6 amps continuous. And with the settup I have now I am running about 15 amps static with WOT so that unloads to 12-13 amps in the air. I am only running less than half throttle most of the time anyway. I need about half throttle to hover. It hasn't cut out on me yet. The motor does get a little hotter than normal but the kokams are in a normal range of warm.

I almost forgot, at the very top of the brochure that came with my battery pack it said that the 1200HC was a high discharge type. I'm not sure what the 1200HD reference is.

< Message edited by tailheavy -- Jul 31 2003 1:36PM >

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       Post #: 34

Li- Poly - 7/31/2003 9:51:34 PM   
Greg Covey



Posts: 4445
Joined: 5/24/2003
From: Rochester, NY, USA
Status: offline 		Just a little clarification for you guys.

JJ Hong is the CEO of Kokam in Korea and he has a vast knowledge of all his products. His 9amp burst rating and 6amp continuous current rating for the 1200HC (aka 1200HD) cell is correct.

I am typically pushing the burst current of the 1200HC cell to 12amps for 5-10 second bursts using good throttle management.

The HC designation was a slight downrating from the HD rating. You will notice that the 1200HC cell has a continuous current rating of 5C while the newer 1500HD cell has a 6C rating. Other new cells like the 340SHC have an unbelievable rating of 20C!

I guess that I can believe it because I am using them.

Here are some places to buy Kokam cells in the USA.

[URL=http://www.hobby-lobby.com/kokam.htm]Hobby Lobby[/URL]
[URL=http://www.b-p-p.com/products.htm]Bishop Power Products[/URL]
[URL=https://www.fmadirect.com/site/home.htm]FMA Direct[/URL]

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       Post #: 35

Li- Poly - 8/1/2003 12:00:50 PM   
tailheavy



Posts: 132
Joined: 5/12/2003
From: Virginia Beach, VA, USA
Status: offline 		I guess that little piece of paper that comes with the battery is a little misleading then cause it say's 8C for high discharge batteries. And right at the top of the sheet it lists the 1200HC under the heading "High Discharge". ??????????????????????

I also guess I am misunderstanding the term "average maximum current". I thought that as long as you're under 8C your good to go. I also thought 8C for a 1200ma pack is = 9.6A. But on the web site for fma direct it definitely states 5C. I am so confused.

But the kokams seem to be working well for me (w/throttle management). Just waiting on my brushless motor to get here then my amp draw should go down.

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       Post #: 36

Li- Poly - 8/1/2003 6:16:40 PM   
JJ HONG


 

Posts: 44
Joined: 7/14/2003
From: SEOUL, KOREA, REPUBLIC OF (KOR)
Status: offline 		1200HD /5c is correct.
new 1500 HD will be 6c continuous.Thanks

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       Post #: 37

Li- Poly - 8/1/2003 7:56:36 PM   
Greg Covey



Posts: 4445
Joined: 5/24/2003
From: Rochester, NY, USA
Status: offline 		tailheavy,

Don't worry about being confused, it is understandable since the Lithium revolution is so new. The fact that you are using Lithium in electric flight means that you are on the cutting edge.

Sometimes, paperwork is wrong and it takes time to correct. The paperwork stating 8C discharge may have reflected the original target but not the production cells for 1200HC. Each cell type is different, even within the same HD catagory.

Lithium cells are now getting several ratings, one is for continuous current delivery and another is for peak short term delivery. Since you use throttle management, you can take advantage of the peak short term rating when picking a cell type or designing your power system.

The 1200HC cell (aka 1200HD) has a continuous current delivery of 5C or 6amps. The peak short term delivery is rated to 8C or 9.6amps. You will find that for short bursts you can exceed the 8C rating without damaging the cells. I often suggest an 8C-10C range for short term bursts on the 1200HC cell, hence the 6-12amp capability.

The even newer 1500HD cells, just hitting the market, deliver a continuous 6C current or 6*1500 = 9000mA or 9amps. Again, the peak current delivery is 8-10C or 12-15amps. This is an impressive cell.

Super high current packs can be made from smaller cells but the cost usually goes up. Look at the [URL=http://www.b-p-p.com/KokamSHCpacks.htm]Bishop Power Products[/URL] site. They make super high current packs from the smaller Kokam 340SHD cells that can deliver up to an amazing 20C! A 3s3p configuration like the Kokam 1020SHC 11.1v pack for $99.95 can deliver 20amps in a 3oz package. Compare that to an equivalent 10-cell 2/3A 1000mAh HECELL NiMH pack at 7.3oz that can only deliver 16amps and you can see why the Lithium revolution is so exciting to the world of e-flight!

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       Post #: 38

Li- Poly - 8/3/2003 9:50:35 PM   
cork


 

Posts: 20
Joined: 3/29/2003
From: HereintheUS, USA
Status: offline 		On the other hand, the Etec 1200ma cells have been able to deliver 8C continuously since they were first introduced and even higher C rates when used as burst. The great part about the Etec cells is that they deliver over 90% of their capacity when used at these high rates. The Kokam 1200HD cells at 8C or even 5C will only deliver about 50% of their capacity at those rates. That is why the Etec cells have become so popular with e-flyers. They deliver more of their capacity under heavy loads. Since the Kokams only deliver 50% capacity, you will get longer flight times by using the Etecs. This has been documented several times in various graphs and reports that have been posted elsewhere.

And then there are the recently introduced Thunder Power lipo cells that may exceed even the Etec cell specs, as they are being tested by several well known e-flyers who are reporting excellent results. The Thunder Power cells are just now becoming available from online vendors and were designed for R/c to replace some of the commonly used nimh and nicad packs as they are similar in size but much lighter. Recent reports have stated that they retain a higher voltage under load than the Etec cells.

Since this thread is about Li-Polys in general, I thought it would be best if all the lipo manufacturers were respresented.

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       Post #: 39

Li- Poly - 8/3/2003 11:42:07 PM   
hoppyfl


 

Posts: 51
Joined: 9/17/2002
From: At Sea
Status: offline 		Cork, those ETEc 1200 cells really are good. They do provide high current for long time.

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