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Turnigy max80W charger puzzle

Liemavick

Member
Mentor
#1
Hey guys I was bench testing my hex 24g 1300kv with a Turnigy 3S 11.1 20c. Long story short is the 30 amp ESC and motor got smoking hot, motor actually started to smell hot. I was thinking Im over propped, so I went to a smaller one. After the ESC and motor cooled I ran it again with same results but cut it short of getting to hot. So now Im scratching my head, motor is rated 11v, battery is 11.1v. To cut this short I went and got the voltage tester and the battery was at 11.87v. I'm guessing I found my problem.

Whats perplexing to me is this charger has a automatic shutoff at what you program it to, ie: Lipo 3s 11.1v. Ive witnessed the auto shut down, but honestly never noticed what the charge was on the battery. I just ASSUME'd since it auto stopped the battery was at 11.1v. For kicks I checked two other batteries I had charged and one other 3s 11.1v was at 12v, and the other was a 2s 7.4v was at 8.5v. All were charged with the auto shut down.

I dont know if you could say this is user error with me being new to the game, but just be aware when your charging with a auto shutdown you may not be getting what you think. If Im doing something wrong aside from not noticing the finished charge level feel free to assist, any and all help is appreciated as usual.

Brian
 

pgerts

Old age member
Mentor
#2
11.1 volts are nominal for 12.4 volts - no problems at all with your 11.87 volts.
What size and brands of props are you using? Are the props centered? Have you got any glue or other garbage in the motor or near the motor axle.
 

Liemavick

Member
Mentor
#3
pgerts, The reason I was bench testing was to see how the motor did with different props. I have a feeling your going to tell me the 10" was to big and the 7" was to small for this motor? A 8x4 I believe is whats recommended. The motor was clean, props were centered. At slow speeds the motor was fine, as soon as I ran it up to about 1/2 throttle is when the heat commenced. So my issue is prop size? Is it that critical that 1" in width would burn a motor out? If Im reading you right the battery issue is a non issue and its looking like the prop selection is my culprit?

It all looked so simple, grab some foam, make a couple of cuts, toss a motor and battery at it and were flying LOL! I have so much to learn.

Thanks friend,
Brian
 

Foam Addict

Squirrel member
#4
Okay, since no one else seems to have seen this, I will chime in. the max voltage per cell of a Lipo is 4.2 volts per cell.
Under load, the voltage quickly drops to 3.9, and slowly descends to 3.5ish before dropping rapidly again.

What I don't like here is the fact that the charger is under charging 3 cells, and over charging 2 cells. The first problem, the motor, is annoying, the charger is dangerous. Please watch your batteries closely, as I don't like those readings.

As to the motor, if a winding was missed, which is far from unheard of, your motor may be something more like a 1500-1600kv motor.

Also,just so you know, a propeller draws a higher current when its platform is not moving forward, so in other words, it will run cooler in the air.

My recommendation is to prop down an inch in diameter or pitch, and then put it on your airplane of choice.
Fly it for 30 sec, land, and see if your motor is hot.

I hope this helps, and GO HAVE FUN!:D
 
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Liemavick

Member
Mentor
#5
Thanks Foam Addict (love the name), Just so I can get some clarity what should a properly 3 cell fully charged read on my volt meter, and a 2 cell? I stay in the area when Im charging batteries so I can keep an eye on the display and stop the process when those numbers are reached, I just thought the charger would do its job with the auto stop. I pick up the batteries several times during the process to check there not getting warm, and always charge at 3 amps so not to rush it.

All your other comments are noted and I will try the testing in the air and see how we make out. One item I left out that also may be an issue is when I was bench testing. I had the hex 24g motor in a pushing direction as thats whats needed for that plane. I'm guessing not having any airflow over the motor amongst other things didnt help the situation. The particular motor in question may be retired with 0 hours flight time, I'm sure I cooked it a bit even though it still operates I'd rather not risk a plane.

Thanks for your input,
Brian
 

jetpackninja

More combat please...
Mentor
#6
12.6v is a full charge on 3s, if you watch the charger as the battery approaches getting full, the charge rate (amps) goes down. Just leave it on the charger until it stops. Do some youtube searches for 4 button smart charges and take a couple of hours to learn about lipo charging. Not familiar with the specific charger that you are using, but all smart multi chemistry chargers work very similar.

Testing for new props- do you have a wattmeter? If you plan on trying different than the recommended props on any setup, get a wattmeter.
With 8x4 being recommended- Almost certainly any 10inch prop will be too big. Also- if you are seeking answers, the pitch is as important to know as the diameter. a 7x6 prop will pull as much power in general as an 8x4...
 

Liemavick

Member
Mentor
#7
Watt meter/alarm combo along with a batch of props and other goodies will be delivered on Thursday. Jetpack, what numbers am I comparing the wattage draw to, max the motor is rated for?? Should I be able to hit full throttle and not exceed that number?

Thank you Sir,
Brian
 

jetpackninja

More combat please...
Mentor
#8
Yes- sort of. If you are at the max rating on the bench, you probably won't be exceeding it in air. But remember that a max rating is a "max" rating, most of these motors will work fine if they are at the max every once in a while, very few will run at the max for very long :). You wattmeter is valuable because even props that are the same pitch and diameter can pull way more or less than another design.
If all this isn't complicated enough, many manufacturers overstate their ratings...
 

Liemavick

Member
Mentor
#9
The learning curve deepen's lol One thing that happened last night that Im still wondering about is the motor shut off at one point. I was running it at about 1/2 throttle for maybe 20secs, then did a quick blast to full and the motor stuttered once and then stopped. I backed the throttle down to 0 and then came back up and the motor spun again. Motor overheat shutdown? battery was at 9.6v at that point, Did the ESC shut it down? Any idea on a guess of what happened? Which component controls the motor to turn off like that? The ESC was a 30amp Turnigy plush.
 

jetpackninja

More combat please...
Mentor
#10
The ESC has a low voltage cutoff. Possible that the batt voltage sagged low enough for the LVC to kick in, then recovered and allowed the motor to spin up again. Hard to tell from here though ;)
 

Foam Addict

Squirrel member
#11
Egad! The Ninja has struck again!
Yes he is correct in every way except one.
Disclaimer if I am a fool for posting this, please tell me!
A better prop tool is the radius of the prop squared times pi times the pitch.
Even this doesn't work for pitches above 8 or below 3.

Yes that was the stock LVC.
I have a programming card which allows me to cut off at 10.5volts for a 3 cell, or 7 volts for a 2 cell.
Even that is a little low, but it works if I forget to land.:p
 

Liemavick

Member
Mentor
#12
Just so Im clear a stock Turnigy ESC will cut the power at or around 9.6v's on a 3 cell? I guess going below 9v is the danger zone on 3S batteries? and 7v's on a two cell? Thats not much flying time unless they are more efficient in the air vs bench testing? Everyones paitence is appreciated while I try to piece this all together.

Thanks,
Brian.
 

Foam Addict

Squirrel member
#13
Highway to the dangerzo.. Oh this isn't TopGun?:eek:
In all seriousness, 9 volts on 3 cell, 6 on a 2 cell. AKA 3 volts per cell.
If you want any kind of longevity though 3.5 Volts per cell is a better voltage. 7 volts on two cell, 10.5 on a 3 cell Etc.

What size of battery do you have?

My Stryker F-27 B (fast and inefficient) has a 3 cell 850 mah, and I still get 3-4 min of flying out of it.
 

Liemavick

Member
Mentor
#14
For the record I have watched Top Gun over 100 times. It was the very first movie I bought on VHS for my new $800 VCR, yes Im old! One of my stocking stuffers a few years back was the Top Gun DVD! Enough derailing my own thread lol To answer your question i have the rookies assortment of batteries:
1- 25c 7.4 950mAh
1- 20c 11.1 2200mAh
1- 20-30c 11.1 3000mAh
-1 20c 11.1 1600mAh that went up in a blaze of glory! I lost signal to my 1st Bloody Wonder (since rebuilt) and it "landed" nose first from about 75ft. "I have a great Polaroid of it" How was I to know the park had a dead spot! They really should post signs LOL
 

Foam Addict

Squirrel member
#15
Okay, 950 when fully charged should be 6 min at full throttle.
the others, I don't think I know a plane that could lift those on a blue wonder!
 

Foam Addict

Squirrel member
#16
Okay, 950 when fully charged should be 6 min at full throttle.
the others, I don't think I know a plane that could lift those on a blue wonder!
 

Liemavick

Member
Mentor
#17
Like I said brother, rookie battery assortment. I bought what I thought I needed from what I read BEFORE I found Flite Test forum :) The 3000 was from a comment over at Mikeys RC about flying all day on it in his FPV3, which I built and have yet to fly. lol
 

Foam Addict

Squirrel member
#18
The FPV V 3 is a good trainer, if built well.
But I recommend that you build the sport trainer. First as specified, next with an armin wing, next with a full fuse.
It really is a great bird.
 

Liemavick

Member
Mentor
#19
Foam, Ive already built and flown the Old Fogey and Bloody Wonder. I also have the FT3D waiting in the wings. Mikeys FPV hasnt gotten airborne yet due to my choice of motor. Along with the mongo battery I ordered I also ordered a high KV motor due to my lack of knowledge. My thoughts at the time were big plane, big motor, big prop. I have since learned thanks to Rob (Bolvin72) a smaller KV motor is what that plane needs to handle the 10" pusher prop.

The weather of late has done anything but cooperate, its either been to windy or raining at times I could fly. I have 4 planes built Ive yet to maiden. Mikeys, the FT3d, and two of my own designs that are going to be intersting.

Which Sport trainer are you refering to? A man can never have enough planes to fly :)

The FPV V 3 is a good trainer, if built well.
But I recommend that you build the sport trainer. First as specified, next with an armin wing, next with a full fuse.
It really is a great bird.
 

Foam Addict

Squirrel member
#20
Sorry,
wrote that kinda late.
The Mikeys Rc sport trainer is what I am refering to.
If built lightly, it can do about anything.
My FPV v3 had no elevon authority, to the point of which I flew the plane by throttle only!:p