PDA

View Full Version : 20C packs?


GallopingGhost
11-25-2005, 10:01 PM
:rolleyes: I've heard mixed reviews on the life of the 20C packs. Hobby Lobby has some at a good price but I have heard they have a short charge, discharge cycle life. Any first hand experience with them?

rocket_jim
11-26-2005, 02:49 PM
I cannot answer your specific question. But I have read and believe it a good idea to be sure up front whether the specified C is Constant or Burst (some short time like 6 seconds out of each 60 seconds). Apparently some mfgs have specified their Burst C, but not labeled it as such and the buyers assumed incorrectly that was constant current, to their regret. As I've read but hope to never see, operating at Burst current means the dreaded sausage in a relatively short time, eventually leading to the real Burst.

I found what struck me as a great LiPo reference at: http://www.fmadirect.com/tech_data/techdocs/ especially LiPo Handbook, Section 3

Rugar
11-26-2005, 03:48 PM
I was real tempted to get one of the Polyquest 20C batteries at the Hobby-Lobby sale yesterday just see how well, how cool, and how long they would actually perform, but decided money was better spent elsewhere. They are claiming these cells are 20C constant, not burst.

http://www.hobby-lobby.com/polyquest.htm

I'm not real clear what the purpose of a 20C discharge rate would be though. Sure you could push the cells hard, but that also would come with extremely short flight times, and these cells also weigh more then a 12C cell of the same capacity.

GallopingGhost
11-26-2005, 10:05 PM
Well its not the first time I took a chance. I went on and got a pair of the 1200 3 cells at $31.00 during the sale. I don't plan to use the 20 C the only thing I am flying now that would give them a test hits about 15 Amps. Maybe they can live with that. I justified it by buying a XT 400 and a pair of Yaks too. The Yaks are hard to beat at $13.00! The XT400 I have is pretty strong and I was real happy to get another at $19.00. So if the batteries end up as hand warmers at least I got something good in the sale.:)

timocharis
11-27-2005, 05:46 AM
gg,

I'll bet they're fine 10-12C packs. I've found the Polys to be a little heavy in the past, but haven't looked at their latest numbers. On the other hand, my old ones are still going strong and seem okay.


Dave

watt_the?!
11-27-2005, 06:29 AM
I'm not real clear what the purpose of a 20C discharge rate would be though. Sure you could push the cells hard, but that also would come with extremely short flight times, and these cells also weigh more then a 12C cell of the same capacity.

Bingo....my sentiments exactly... 20C is 3 minutes to draw everything from the pack...so pulling 20C must mean less than 3 minutes flight time.

30C is even more crazy...2 minutes!?

i think that the rating has merit, but not for application in practice.

perhaps a better rating would be 90% V for 10 minutes or something like that...

timocharis
11-27-2005, 06:58 AM
A real 20C flight pack that comfortably delivered that current level while trading down the weight proportionally would be a real boon to ultrasmall 3D types. I'd love to drop another 1/2 oz just for kicks!

Sometimes I fly in my 8x10 spare room, and I've never lasted 3 minutes. Well, rarely.


Dave North

TManiaci
11-27-2005, 07:53 AM
The "expert" at my LHS says the 20C bateries are just not worth it yet. They will only go 30 cycles if you work them hard. He said... "think of these like fuel cost on nitro planes..." :(

I have looked at several of these big "C" batteries... they just do't push into the "next generation" that some seem to think. They generally weigh considerably more than same-mAH 12 & 15C batteries. True Next Generation batteries will take a 2100 mAH to a 1320 mAH weight class, with 20C... IMHO - just delivering more current, with a higher weight, serves little pupose... unless you like far less fly-time. With reduced life and high prices... not interesting.

Bigfoot21075
11-28-2005, 02:55 PM
I have the 3300mah 4 cell 20 packs they sell. They a great packs. I have not measured the strain I put on them, but so far they seem fine. I have not heard anything negative about these particular ones.

bert269
03-29-2006, 08:31 PM
Bigfoot21075 (http://www.wattflyer.com/forums/member.php?u=4338), do you have any update on these packs? are they still around and working....or trashed already?

Thanks
Bert

Bigfoot21075
03-30-2006, 10:42 AM
Bigfoot21075 (http://www.wattflyer.com/forums/member.php?u=4338), do you have any update on these packs? are they still around and working....or trashed already?

Thanks
Bert

Hi Bert!

Yes the packs are hanging in there. I have flown them on mornings as cold as 21 degrees and have flown some strenuous flights on other days. So far they are the same as when I began using them. I still get more than 10 minutes in my 65" Decathlon running an AXI 28/26 10

Unbalanced prop
03-30-2006, 02:08 PM
I bought a couple Hyperion VX 20C 1500 packs to use in a MUS. I do not plan on running them at 20C only a max of around 14C. So far I have only bench tested these. One of the biggest advantages I can see is their ability to hold a high voltage under load, which means higher RPMs and Watts (Power!!). This also means higher AMPS, so you better check the amp draw on your setup when switching over to these type of cells. Don't want to fry an ESC or motor!

http://www.wattflyer.com/forums/showthread.php?t=5650

Doug