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HelicopterMain Discussion › my heli doesnt fly :((
12-21-2003 04:20 PM  13 years agoPost 1
Kocur

Heliman

Poland

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Hello
My Q15 converted to electric with hacker b50 11l and lipos (3sp4)
hovers only for a few seconds, then rotorhead slows down and my heli
lands.What to do? I have 10t pinion.

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12-21-2003 04:22 PM  13 years agoPost 2
Hivoltage

Senior Heliman

Ohio

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Sounds like you are not properly getting the battery charged!!!!!

I Dont Have No Stink'in Signature

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12-21-2003 04:26 PM  13 years agoPost 3
Twobeers

Key Veteran

Toronto, Canada

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Not being an expert of electric heli's, but a fairly knowledgeable electronics technologist I will take a stab in the dark here. Possibly your pulling to much pitch causing the motor to have to work much harder, there by causing a excessive current draw which is depleting your battery pack to quickly. I assume that you have made certain that there is no abnormarl drag/friction in your drive train which would also add to the problem (i.e. gear mesh to tight).

I lost my infamous tag line.

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12-21-2003 06:13 PM  13 years agoPost 4
Ralphw

Key Veteran

Spring, TX

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A B50-11l on a Quick E (assuming that your conversion uses the same gearing) should give you about 2200 rpm head speed with the 10t pinion and a 3s LiPO pack(no load). From your description it sounds like a battery problem as the most likely culprit. What brand and mah rating is the battery you are using? Also what charger and settings?

Other areas to check would be throttle and pitch curves as well as excessive drag/friction. I found that the tail belt being overly tight can cause a higher than normal amp draw as the motor worked to overcome the friction caused by the belt. Also, remember an electric motor (in a heli) generally does better at the high end of it power curve (85% and above) and will run cooler and longer in that zone. I run the throttle curves for the C40 in my VE Extreme at 90% straight across in Idle-Up 1 and am at 85% at mid stick in "normal". Once I have the throttle curve right then I set the pitch curves to get the desired result.

Ralph W.
"Life's Short, Fly Fast"

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12-21-2003 07:41 PM  13 years agoPost 5
Kocur

Heliman

Poland

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I use Thunder power 7800 mAh 3sp4 pack. I tried 80% and 100% throttle in gov mode.
The problem maybe the charger i use.Its cheap and very simple, but i
think its not it. I charge the batterys for about 6 hours with 1.5-1 amp draw.

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12-21-2003 08:30 PM  13 years agoPost 6
Ralphw

Key Veteran

Spring, TX

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Kocur,

If the charger you are using is not rated specifically for Lithium Polymer batteries....STOP. Use of the the wrong charger can and has led to permanent damage to the battery and in some cases fire (yes, even at relatively low charge rates). From your description of the problem it really sounds like that is where your problem is. AstroFlight (as well as others) makes a relatively inexpensive charger for only LiPO's (I think the model number is 109) that several people I know are using and they are very happy with it. But for your own sake, please don't use a charger that is not designed for LiPO...you may not like the result!!!!

Ralph W.
"Life's Short, Fly Fast"

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12-21-2003 08:45 PM  13 years agoPost 7
Kocur

Heliman

Poland

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This charger IS designed for lipos. Batterys dont even get warm after charging. I think the problem is somewhere else.

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12-21-2003 09:52 PM  13 years agoPost 8
KnimRod

Senior Heliman

Central Michigan

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It does seem like a battery or charging issue to me. It's easily checked however.. Simply measure the battery voltage with your volt meter. If it's low after charging, it's likely a charger problem. If it's low after a few seconds of flying, it's likely a battery problem.

Completely discharging a fully charged 3S4P pack over 1 minute is about 6 KiloWatts. Complete discharging over "a few seconds" would likely result in a small mushroom cloud over your heli.

What charger are you using?

Lance

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12-21-2003 11:33 PM  13 years agoPost 9
Ralphw

Key Veteran

Spring, TX

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Kocur,

Didn't mean to insult you, just didn't want you to burn the house down right before Xmas !!

Just a thought here, but is it possible that instead of getting a 1 amp charge rate you're actually getting 1 mah (as in 1 vs .1)?? Not that I've EVER made that mistake . As Lance said, check your voltage right after charging and then again immediately after landing with a decent DVM. On the 3s pack, you should have between 12.48 and 12.68 volts after charging (straight from the Thunder Power website). Recommended minimum voltage after discharge is 9 volts for the 3s pack, anything lower risks permanent damage to the battery. Last but not least, the "recommended" charge rate is 2000mah up to 7800mah (1c).

As for the problem being elsewhere...possibly an overheat of the ESC...although most ESC would simply shut off in that situation. Your description sounds exactly like my heli when the voltage would get low using the NiMH batteries...hover then slowly sink back down as the headspeed decayed. I have no idea what the LiPO's do when the voltage gets low since I don't discharge that far.

One other thought...it could be that your charger is detecting a "false peak" in the battery and is shutting off the charge too early. When you recharge the battery, how long does it take before the charger indicates it's ready??

Hope all this helps...

Ralph W.
"Life's Short, Fly Fast"

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