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shaf
12-23-2010, 01:34 AM
I am new to electric flying so I'm not sure what is going on. I have a fairly new E-flite #15 840kV motor that has given me problems. As I advanced the power the rpm would come up and then fall off and hold at about 40%. Thought it might be the speed control but swapping that out brought no relief. Then swapped the motor and all seems to be well. The motor is in an E-flite Apprentice using a 3S 3200ma battery. The motor only had about a dozen flites on it. Any thoughts?

Shaf

rcers
12-23-2010, 01:47 AM
About 95% of the time it is the battery unable to provide the juice. So what size prop do you have on that?

And as you get into electric - the Watt meter is your most valuable tool, it tells you what is going on! It is hard to guess, and the meter shows you watts/amps and in this case importantly voltage. You can tell a tired battery as it won't hold voltage under load.

So did swapping the motor solve the issue? Sorry just re-read your post.

Mike

shaf
12-23-2010, 02:01 AM
Motor seems to have solve problem. Tried two different fully charged batteries. Problem developed progressively over the past two or three sessions/days.

CHELLIE
12-23-2010, 02:52 AM
Motor seems to have solve problem. Tried two different fully charged batteries. Problem developed progressively over the past two or three sessions/days.

The problem could be a bad motor or you could have cleaned up the esc to motor connection when you swaped the motor, check the esc and motor connection to make sure its clean and tight, if it ok then check the problem motor with a Volt / ohm meter, there are threads on watflyer on how to test a brushless motor, Hope that helps, Chellie

foamjetpilot
12-23-2010, 04:28 AM
Does the power loss come on the first flight? On the 2nd flight was the motor and ESC cool to the touch? What is the C rating on your battery? What size prop? I had this happen with my Super Mega Jet motor on the 2nd flight immediately after some spirited flying. Motor was still warm and on the 2nd battery at full power, it sputtered. 40% power was smooth running. Make sure the batteries are in balance too and if you ever puff a battery pack, use caution with every chargie and use. Watt Meter is needed and try this too (Digital voltage display). http://www.graysonhobby.com/catalog/electronic-accessories-c-49.html Make sure to read the instructions for an accurate reading. Will work on 3 and 4 cells, you just plug the meter one wire down from red on a 4 cell. 3 cell you plug in once and it displays the volts for each cell. Good luck.

shaf
12-23-2010, 12:30 PM
When the problem first appeared it was intermittent. Yesterday it happened on the first flite. Could not even get in the air and yest it ran smooth at reduced RPM. I have 2 batteries, one 15c and one 30c. I think the connections were good as we swapped esc's withno change but when we changed the motor all seemed well. Have not flown it yet but have run it up at least a dozen times. I assume I can use the 15c and 30c interchangably?
the batteries are both 3s 3200ma.

Thanks for the help. I'm still learning

Shaf

rcers
12-23-2010, 01:53 PM
Well if you swapped motors and the problem is solved you know it is a motor issue. I have never had a motor fail - like that. Strange, but they ahve a good warranty, send it in see what they say.

And yes you can use the both batteries as long as you are not exceeding the rating. That is what the watt meter helps with too.

Mike

Grasshopper
12-23-2010, 02:59 PM
Maybe a stupid question, but when you swapped motors, was the second motor and prop the exact same type as the first one? Just asking in case it is different and drawing less amps than the first one.

FlyingBrick50
12-23-2010, 03:23 PM
"I have 2 batteries, one 15c and one 30c"
That is your discharge rate

DigitalVI
12-23-2010, 11:03 PM
When the problem first appeared it was intermittent. Yesterday it happened on the first flite. Could not even get in the air and yest it ran smooth at reduced RPM. I have 2 batteries, one 15c and one 30c. I think the connections were good as we swapped esc's withno change but when we changed the motor all seemed well. Have not flown it yet but have run it up at least a dozen times. I assume I can use the 15c and 30c interchangably?
the batteries are both 3s 3200ma.

Thanks for the help. I'm still learning

Shaf


I am willing to bet this first started after you nosed over once. This happened to me once with mine. I think the motor shaft bent or the motor case (plastic) cracked near the shaft. Replacement shafts are available, and Horizon was very good about replacing the motor for me.

Dan

foamjetpilot
12-23-2010, 11:30 PM
Shaf,
Motors are cheap, maybe order a new one and the watt meter at the same time? Both are good insurance, You may not want to risk damaging the plane and radios in a potential crash. Plus your time to rebuild.