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T-REX 250 › Can't keep it up!
03-22-2009 04:12 PM  8 years agoPost 1
schnej

rrNovice

DAYTONA, FL usa

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Need some help guys... I think this is a battery issue. Anyways, the 250 is built and went together smooth. Longest flight to date is about 15 seconds. Flies well when it does!

I'm using a CC Phoenix 25 speed control with the stock motor. Headspeed gets into the high 3000s on the bench with "hover" pitch. I'm confident my pitch and throttle curves are acceptable (not finetuned) and pitch is set per manual for normal mode. Changing ESC govenor mose didn't make a big difference either.

Then it was time to fly, alas it barely gets off the ground. When it does, it reaches about 10 feet, and things start sloooowing down, and gently returns to earth. If I wait 30 seconds, I can repeat.

SO, is this what happens when old lipos bite the dust? 1100mah 12C PolyRC - flew quite well on a Piccolo Pro last summer (a slightly heavier bird). I mounted on the bench and watched pack voltage at full power drop 11... 10... 9 volts and below as the motor lost power (maybe tripped the Lipo cutoff?).

TIA
Jeff

pretty sure i promised a boat and diamond before another bike...


<i>liar!</i>

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03-22-2009 04:15 PM  8 years agoPost 2
george0079

rrElite Veteran

USA

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Your battery sounds like your problem. It doesn't have a high enough C rating. The 250 really needs a 20C, or better.

Hell... I can fix that.
Uh oh..
Nope.
It's ***ked!!!
RE-KIT!!!!!

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03-22-2009 04:20 PM  8 years agoPost 3
inkspot1967

rrProfessor

Cranston Ri

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headspeed at 3000 way to low needs to over 4000

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03-22-2009 05:14 PM  8 years agoPost 4
caseyjholmes

rrElite Veteran

Portland, Oregon

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Yeah 12C is on the low side. Sounds like the lipo is gettin' old too if you had it last summer. Used it since then? How was it stored?

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03-22-2009 06:35 PM  8 years agoPost 5
schnej

rrNovice

DAYTONA, FL usa

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Thanks for the quick replies.

When I initially set throttle curve/headspeed, I was high 3000s (3700-3800). I did this with blades near 0 degrees since I use the ESC in RPM governor mode. Is this a reasonable approach? I'm not flying any headie 3D, so figured I don't need the HS too fast.

Batteries we're used much since about September, but I did run them through a discharge/charge cycle a few times over the winter. Probably left them changed... I think I was treating them like NiCDs, which I know isn't the best. They were pretty cheap batteries so I'm not fretting over it. Like I said, the Piccolo at about 365 grams (IIRC) flew great with them.

Anyways sounds like I killed the lipos so I'll get some ~20C packs and see what people are recommending for fit. Than, and learn how to take care of them. Otherwise I think this is a nice little bird. And the tail seems to hold a little better than I've heard from some...

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03-22-2009 07:43 PM  8 years agoPost 6
inkspot1967

rrProfessor

Cranston Ri

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rpms still need to be way over 4000 some are running 5000 or better i believe so your no way near what it needs to even take off correctly

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03-22-2009 09:03 PM  8 years agoPost 7
caseyjholmes

rrElite Veteran

Portland, Oregon

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Try the align 20C packs. Good balance of budget/power/availability/weight.
For higher end packs I like the Thunder Power Pro Power 850 30C.
Have not tried outrage still.

The tail does hold better than it sounds. Some just get a little wiggle or a blowout here or there and it's usually manageable or tweekable to remove it. So far, no real tail issues for me, even before I added some modifications.

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T-REX 250 › Can't keep it up!
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