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Is it just me?

Old 04-29-2006, 04:44 PM
  #1  
cosmic1
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Default Is it just me?

Is it just me or are the lipo manufacturers going the opposite way on the size and weight of their product? Isn't that the reason we started using lipo's for rc? With the hyped up high discharge rated cells with the same mah they have grown in size amd weight...Many rc aircraft have a very limited battery compartments.. I have a few that anything over the size of a tp 1320 won't fit.. Seems to me its heading the wrong direction!!! Maybe it is just me as no one seems to say anything about that including the manufacturers..
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Old 04-29-2006, 05:47 PM
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everydayflyer
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I agree and since you have already mentioned the TP 1320 here are examples which I have in hand.

The X-Power Gold 20C and , Electric Power 20C 3S 1000 mAh weigh the same as a TP Prolte 3S 1320. I have a Thread here which denotes the same thing. For a 8A average fligh the 1000 mAh 20C have to be used at 8C while the 1320 only has to be used at 6C.
Yes the 20C will do better at higher amps . if you really need 12-16A cont. but then that is only a 3-4 min. flight.



http://www.wattflyer.com/forums/showthread.php?t=6426

Charles
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Old 04-29-2006, 08:10 PM
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t. edwards
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I agree also. I have TP PL 1320's and 2100's. My motors are sized and propped so full throttle amperage corresponds to the cells "continuous" rating. No heat issues, small light cells and reasonable flight times for recreational flying. Has anyone graphed a discharge curve with a motor and esc set full throttle (non constant amperage but real world) and compared it to a cba graph (constant amperage) set for the same starting amperage, same battery? Seems like it would be interesting. Tom
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Old 04-29-2006, 08:37 PM
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Bill G
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The first gen lipos under 1000mah (around 5C) were basically useless to anything other than an LPS setup. Sure, they worked, but it was pushing the batts too hard. The C ratings are up, but the industry still pushes batts for applications that are really pushing the batt a bit. It is no surprise that the TP1320 has become one of the most popular overall parkflyer batts. I think they determined what size would be the largest lipo that could fit most parkflyers, while still having the power needed for the average parkflyer setup, including lower power EDFs.
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Old 04-29-2006, 10:46 PM
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Doc Pete
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Yeah.
I have a 900 TP which is 2oz., while my new 700 common sense batt. is 2.4 oz.
However, the 900 is 10/12C and the 700 is 15C. If this is the way of the future, I hope they offer us a "Choice".
My Yak only needs 10A at full, so the 900 is much better for weight savings "and" run time.
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Old 05-01-2006, 02:32 PM
  #6  
Matt Kirsch
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Two points here:

1. You don't HAVE to use the 20C technology. As some of you have alluded to, or outright said, at one time or another: 10C is plenty for many/most applications. 10C is also lighter and less expensive.

2. 20C batteries are not larger and heavier due to some vast conspiracy to pass larger-capacity cells off as smaller-capacity ones with higher discharge ratings, at least when reputable vendors are involved. It's all simple physics: Higher discharge rates generate more heat, and the battery needs more THERMAL MASS to absorb and dissipate that heat. A physically bigger, heavier battery will stay cooler longer under higher discharge rates.

There are some advantages to 20C, however. 20C holds higher voltages than 10C for the same Amps, which means you have more power and better performance. 20C stays cooler than 10C for the same Amps, which means more of the battery's capacity is usable for flying, instead of heating the inside of the airplane. Overall, the battery is not as stressed, and will last longer. Plus, they're still signifigantly lighter than NiCd or NiMH for the same capacity. I think some of us have become "spoiled" over the last few years with respect to that...

This brings me back to point #1: You don't have to use 20C. Nobody's forcing you to. If the lighter, smaller, lower C batteries float your boat, then by all means, sail on!

Eventually, we'll start to see the size and weight of the higher C batteries come down.
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Old 05-01-2006, 03:45 PM
  #7  
electriconly
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Default It's just you.......

Depends on what you fly..... for light foamies the 20C just make little sense......but....... if you fly 40 to 60 sized glow conversions or electric helis they make a lot of sense.

Example...... my Logo 10 heli

the standard battery is:

4S3PL ThunderPower
weight 488G
cost $258.00

or

4S1P Hyperion Litestorm 3700
weight 335G
cost $167.95

Even factoring the additional capacity of the TP the equivalent weight/cost of a 4S2P would be 325G and $172.00. But many feel the 2P ThunderPower does not hold up in a Logo10. Flight time is shorter with the Hyperion but it still is between 9 and 10 minutes.

Another example my converted Ultra Stick 60

used to use (20) GP3300 Nimh, (2) 10S 3300 packs weighing 710G each or 1420G all up

now use (2) Hyperion Litestorm 3S1P
weight (2) 262G each - 524G total
cost (2) $118.95 each - $237.90 total

I could build the Nimh packs for about $80.00 a pach so the Hyperions cost $77.90 more than the Nimh but I'll spend that any time to save 896G in weight.

Brad
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Old 05-01-2006, 05:20 PM
  #8  
Fred Marks
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Originally Posted by cosmic1 View Post
Is it just me or are the lipo manufacturers going the opposite way on the size and weight of their product? Isn't that the reason we started using lipo's for rc? With the hyped up high discharge rated cells with the same mah they have grown in size amd weight...Many rc aircraft have a very limited battery compartments.. I have a few that anything over the size of a tp 1320 won't fit.. Seems to me its heading the wrong direction!!! Maybe it is just me as no one seems to say anything about that including the manufacturers..
http://www.rcuniverse.com/forum/m_3559995/tm.htm shows why Li Pos are available in a range of energy density. Those who would try to tell you that lightweight is the only way to go do so for the reason of advocacy for their sponsor. Lightweight is fine if you use it within its limitations and high C is just dandy where you need it. However, with rare exceptions, life cycle is the thing that saves you money. It is not difficult to design the pack you need to do your specific application. Use LIPOCALC II at http://www.fmadirect.com/tech_data/lipoCalc/index.htm

One thing for sure is that you do not want to select light weight, then load it as if it were heavier. This is the legacy of blind advocacy of lightweight by unabashed supporters of one particular vendor in which beginners as well as all were exhorted to use only lightweight and suffered the consequences.The results of that are what shows in http://www.rcuniverse.com/forum/m_3559995/tm.htm Use what fits your needs best.
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Old 05-01-2006, 10:26 PM
  #9  
cosmic1
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The weight isn't that big of a issue neither is the c rating 12-15 is fine and I'm conservitive as far as amps go.. The pack size is what I see going up..
2 3/4 going to 3-4 inches does limit the what you can use in smaller plane battery compartments.. It seem that many are going to larger sizes instead of keeping the same dimensions wether increasing the discharge rate or not...
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