440GTX

need a lipo for my Multplex twister

Het 2W in a Het 6904 Fan
with a TP 3S 2200 25C V2 extreme. 185 grams Good for 55 A
40Amps and 400 Watts at 11.1 V
890 grams AUW
Flight time 4.5 min mixed with 60% to 100%

Question .
LHS has 3S 3200 20 C packs which weight 220 grams Good for 64 A
and also 3S 3300 25C packs which weight 275 grams. Good for 82.5 A

Will I notice a difference with the 25C pack or go with the less weight
20 C pack

Thanks in advance
Fred..

Swift427

The deal is that NO ONE knows how many performance cycles these LiPos are good for at their 20C & 25C rate maybe 12 cycles, maybe 25.

Some would go so far as to say that the C discharge rating is just an arbitrary number. In other words it gives some indication of a batteries ability to discharge more amperage without going over 150 F and hopefully not over 140 F. The thing is that you never know the true discharge ability until you find out how many cycles its good for at 80% of C. IMO, I wouldn't suffer a LiPo to more than 75% of its C rating even if I paid $200 for a first class 3S 3200 20C pack. Then I might even figure the packs are closer to 3000mAh & 3100mAh. But if money is no object and you don't care if you only get 12 performance cycles than GO for it.

.75 x 20 = 15 x 3.0 = 45A (max cont discharge if I expect to get more then 25 cycles) with reasonable care.
.75 x 25 = 19 x 3.1 = 59A (max cont discharge if I expect to get more then 25 cycles) with reasonable care.

440GTX

Thanks for the info.
Currently my set up is 40 A draw at 11.1 V with a 3s 2000 25 C so I am discharging at 72 % at WOT
So if I buy the 3S 3200 20C pack I am discharging at 62 % ( better )
The 2 packs are only $12.00 apart ( no big deal ) but the 20C packs weighs 55 grams less.
That is over 5% of my AUW. So I think I will by the 3200 20 C pack
I am a firm believer Less Weight = Better Performance

Swift427

Tradeoffs, Tradeoffs, Tradeoffs (finding a happy medium that suits us)

It is suggested that electric pilots set their LVC so that the bounce back voltage reaches 11.1v after 1 hour from LVC. Most of the BB occurs within 10-30 minutes so depending on your LVC it may BB to 11v within 30 minutes. And then again maybe 10.8v is good enuf – don’t really know?

Because there is such a sudden drop off in voltage from 10v to 9v a pilot is only gaining a few more seconds of flying time from 10v to 9v. You will extend the life and performance of your LiPos by using a LVC that ensures a BB to 11v.

Temperature is the final determining signal as to the quality of the pack whether you can in fact discharge at 80% of C without overheating/ruining the LiPo. You don’t want your packs to exceed 140F. If you estimate your flying pattern is 80% of your LiPo’s C rating and the pack doesn’t go beyond 140F you have a GOOD pack. If it goes to 145F at 70% of C, but you don’t need more than 65% of C for your flying interest then a less expensive pack MAY be the way to go assuming its cells are equally matched, but the vendor just over rated its mAh capacity and/or C rating. Whether you pay top dollar for a quality pack the likes of an Enerland or Kokam depends on your budget and flying interests (pylon racing vs slope soaring).

Time Will Tell!

Consider adding a battery monitor to your arsenal –
http://www.headsuprc.com/servlet/the...ter-for/Detail
http://www.bphobbies.com/view.asp?id...7&pid=B2632602
http://www.all-battery.com/index.asp...OD&ProdID=1973

UnitedHobbies sells one for $4.95. If you have an account with them might as well buy three as one of them may not be reliable. It is shown in LiPo Charger category.