Tony Pacini

Just got a GWS Dragonfly and I'm currently using a 1040 2-cell Li-Poly pack. When it's fully charged it hovers at just under 1/2 throttle (which I think is good) but within 30 seconds or so it takes 3/4 throttle to hover. After a minute it won't get out of ground effect. If I try to charge the battery it takes less than 100 mAh to top it off. Thinking that extended hovering may be too much of a load for the battery I've ventured off into forward flight (at reduced throttle). Again, after a minute or so, it just falls out of the sky. Oddly enough, after letting it recover (unplugged) for a minute or so, it retains it's original power and I can resume flying again. After dozens of flights I've never been able to pump more than 2 or 300 mAh into this battery during a charge cycle.

Is this normal for an electric heli with this size battery? Is this battery a dud? I've got others on order but they haven't arrived yet so I don't have anything to compare to. The standard 750 mAh Ni-Mh pack dies in about the same amount of time.

Help!!!!!

Pahtcub

I dunno about you but I had the same problem when charging my LiPos on my Super Brain 969, I found out that the voltage and mV rates they give in the manual are WAY too safe, I forget what I charged it at but it took a good hour (checked the temp constantly) and man that thing flew for EVER! Check your voltage when you can't get off the ground. If it's under what the battery is rated, then it should take a while to charge.

Pat

Tony Pacini

I'm using a Triton at 1.1A and 7.4V (basically the 2-cell setting at 1C). My other Li-Pos charge fine this way (smaller 340 mAh packs) that's why I think it's a problem with this particular battery. I guess I'll try the other packs when they arrive tomorrow and see if they last any longer.

Thanks for your input!

Poll

I've heard the max on a lipo cell to be 4.2v, so that's up to 8.4v with two cells, not sure what people usually charge it up to, but like Pahtcub said, just check the temp.

quaker1

Sounds like a dud, has it dropped below six volts at any point?

Tony Pacini

duhhhhhhhhhh-

Suppose I ought to check that. Got a pair of new 1200s today (charging now) and we'll see how they do.

Poll

Holy rubbish. Since we're talking about lipos here thought I'd post this, from the eletric flight forum under the power source thread.
"The cells and packs now available as 20mah, 48 mah, 145 mah, 340 mah, 1500 mah, 2AH/15C and 2.1AH/20C are in stock and shipping. The current KOK700HC, KOK 1020; KOK 1200; and KOK 3270/5C cells and packs will be discontinued for RC when stocks are depleted. Five new cells, added to the 20mah; 145mah; 1500 mah; 2AH/15C and 2.1AH / 20C series now mean that all Kokam cells/packs for RC are from 8 to 20C continuous and 14 to 40 C peak HDR depending on the model. Those five cells are:

1. SLPB 533459H4 (740 mAh, 20C/40C) 5.4 mm T X 33.5 mm W X 52 mm L; Weight: 21g. Projected ship date: Sept 2004
2. SLPB 393459H3 (640 mAh, 15C/30C) 4.4 mm T X 33.5mm W X 58.5 mm W; Weight: 17 g
Projected ship date: Sept 2004
3. SLPB 593459H3 (910 mAh, 15C/30C) 6.2 mm T X 33.5 mm W X 58 mm L; Weight: 23 g
Projected ship date: Sept 2000
4. SLPB 7543125H (3200 mAh, 20C/40C) 7.6 mm T X 43.5 mm W X 131 mm L; Weight: 82.5 g
Kokam Engineering, Ltd states that sample quantities will be available for our evaluation in late Sept to Oct, 2004. Please watch www.fmadirect.com for announcement of production inventory. We will work diligently to have these cells and packs for you to put in your Christmas stocking. With those dimensions, they will slide into a stocking nicely!
5. SLPB 554374H (1250 mAh, 15C/30C) 5.4mm T X 43 mm X 51 mm L; Weight: 34g
Available now "

Check out the weigh of the 3200 mAh, 82.5g! also 20C continuous discharge rate, that's insane.

Tony Pacini

I'm now convinced that it's an issue with the brushed motors overheating rather than a problem with the battery; the two 1200 li-pos I just got behave the same way.

It never really stays trimmed for a hover; constantly changing throttle setting and tail rotor trim. Let it rest for a few minutes, fire it up again (on same battery), then it has more power and is out of trim again.

I really dig hovering this little thing but it doesn't seem to handle more than a minute without having to land and let things cool off. Forward flight isn't a whole lot better; even at reduced throttle it loses power after a minute or so and I've got to land it because it doesn't have enough power to stay in the air. Is this just the nature of the beast?

Would a brushless setup (at least for the main motor) help this situation at all? If so, is there an ideal motor and controller for this particular heli?

Thanks for all your help.