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wraith0078
03-28-2007, 03:14 AM
So I stopped by the LHS tonight. (Mistake #1) :D

I've been wanting to get something smaller than my .60-.90 Edge 540 w/Saito 125 so that I could take off from work at lunch time and go fly. Long story short; I made a bit of an impulse buy... :o

Seagull Extra 300 EP
E-Flite Park 480
E-Flite 40A ESC
1650mAh 3-cell LiPo battery
Thunder Power Charger
4x 15 oz/in sub-micro servos
Gonna re-use the JR radio system that I currently have in an old trainer.

Should be a decent lunchtime stress-reliever, right?

Anybody wanna give me the quick and dirty on the care and feeding of LiPo batteries? Used to race cars, but when I did, NiMH was still the "new stuff". The battery pack says it can only handle bursts of 19.8 amps. Will it be okay with the motor/ESC I got?

CitaFly
03-28-2007, 04:25 AM
Short answer - no.

The 480 will draw 22 continuous and 28 burst. This battery will be overtaxed and either die fairly quickly or worse, catch on fire. The 480 spec sheet recommends 30 amp continuous if using a large prop.

wraith0078
03-28-2007, 04:59 AM
Thanks for pointing that out. I suppose if I had read the motor box, I wouldn't have had to ask...

I'll take the battery and/or motor back.

Thanks again.

Sky Sharkster
03-28-2007, 05:00 AM
Hello Wraith0078, Welcome to Wattflyer!
Here's a couple of links with battery info. The first is short and concise, just the basics; http://www.redrockethobbies.com/RC_Airplane_Battery_Basics_s/263.htm
And here's a comprehensive version, it's good material and FMA Direct makes a great charger, too!
http://www.fmadirect.com/lipo_handbook/FMA_Lipo_Handbook_Section3.htm
Hope it helps,
Ron

Solid Hit
03-28-2007, 12:46 PM
Short answer - no.

The 480 will draw 22 continuous and 28 burst. This battery will be overtaxed and either die fairly quickly or worse, catch on fire. The 480 spec sheet recommends 30 amp continuous if using a large prop.
Did I miss something? Wraith has a 40 amp esc listed.

Other then that, it seems like a good setup.

Don't neglect to balance/charge the lipo.

Sky Sharkster
03-28-2007, 01:27 PM
Hello Bill and Wraith,
I believe CitiFly is referring to "C" rating and amp draw. The 1650mAH battery, if rated at 10c continous, would deliver 16.5A, about 1/2 what the motor is rated for (full throttle). Even at 15c, the output would be 25.05A, still below the motors 28A "burst" rating. The highest reliable battery rating I've seen, 20c would be 33a, barely above the 30A recommendation from the motor manufacturer.
So the motor is trying to pull more amps than the battery is capable of delivering and the 40A ESC is rated (more than) high enough to let it. Result; Thermal overload, meltdown.
Since Wraith didn't specify the "C" rating of his battery, CityFly is correct in assuming it's 10c to 15c, the most popular output ratings available now.
For this motor, I'd say a combination of s/p and mAH capacity that equals 35-40 amps continous would be safe.
Just my $.02,
Ron

wraith0078
03-28-2007, 03:14 PM
Hello Bill and Wraith,
I believe CitiFly is referring to "C" rating and amp draw. The 1650mAH battery, if rated at 10c continous, would deliver 16.5A, about 1/2 what the motor is rated for (full throttle). Even at 15c, the output would be 25.05A, still below the motors 28A "burst" rating. The highest reliable battery rating I've seen, 20c would be 33a, barely above the 30A recommendation from the motor manufacturer.
So the motor is trying to pull more amps than the battery is capable of delivering and the 40A ESC is rated (more than) high enough to let it. Result; Thermal overload, meltdown.
Since Wraith didn't specify the "C" rating of his battery, CityFly is correct in assuming it's 10c to 15c, the most popular output ratings available now.
For this motor, I'd say a combination of s/p and mAH capacity that equals 35-40 amps continous would be safe.
Just my $.02,
Ron

You sir, are correct! Long story short, I walked in to the store 30 minutes before closing time and made an impulse buy, so both me and the guy that sold me the stuff were in a hurry and missed that small detail.

The battery I bought is this one: http://www.commonsenserc.com/product_info.php?cPath=37_35&products_id=55

I'm going to return it and exchange for this one if they have it in stock: http://www.commonsenserc.com/product_info.php?cPath=37_25&products_id=39

CitaFly
03-28-2007, 03:26 PM
Glad you asked and we were able to help.

Ron - thanks for fleshing out my anemic response. I assumed that the burst rating wraith0078 stated in his first post was based on the burst C rating mutliplied out by 1.65, since it's an odd number.

Working back from 19.8:

19.8 / 1.65 = 12 - and this for Burst!

Turns out the back-of-the-envelope method was not too bad:

"This is a single 3 cell Lithium Polymer 1650mAh battery pack. 8C continuous discharge rate not to exceed 13 amps."

A Viking Funeral in the making.

wraith0078
03-29-2007, 01:51 PM
Okay, the battery has been exchanged for a TP 25C 2070mAh pack. :D

Max continuous discharge: 50A
Max burst discharge: 103A

Should do the trick.

Thanks again for helping avert a disaster. :cool:

wraith0078
03-29-2007, 11:29 PM
Another question just came to mind. How long of a flight time can I expect with the Park 480, 40A ESC, 2070mAh battery and 10x7 prop?

CitaFly
03-30-2007, 03:31 PM
Depends on throttle management and what this setup will draw, but without using a wattmeter, the motor's spec is continuous current of 22 Amps. If you were to run at wot:

ttl min = (2070 x .06) / 22 = 5.6 minutes.

The more sedate you fly, the longer the flight time - I would guess 10-15 minutes is more likely.