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Old Jan 11, 2013, 12:15 AM
Wonderfully Wicked
The Don's Avatar
Willoughby, Ohio
Joined Jan 2002
12,970 Posts
I have found puffing for me is a direct result of discharging too low. Just one instance of flying to LVC will result in the lipo puffing about 3-5 cycles later when used in an EDF application. If I happen to go below 3.5 volts/cell at rest then I am in dangerous territory. My ESC is set to its max of 3.3/cell and if I actually hit that and the ESC shuts off in flight, these new high C lipos will not rebound voltage like the old days. They will stay low about 3.3-3.4 not bounce back to 3.7 so if I hit LVC on and EDF in flight I know I toasted the lipo for EDF use. I typically mark the pack then use in a lower C application. If I keep using it in the EDF, the in about 3-5 flights later the pack will puff on me. I have not found any brand lipo that does not do this. So that is why I only fly by timer. I do not know why lipo manufactures do not suggest much higher LVC values these days. It is so easy to kill a lipo C rating by going below ~3.3 volts per cell. I get several emails a week from people who have 40C lipos and yet the ESC keeps hitting shutoff after one minute of flight time and they don't know why, or they get much lower watts than they should, and it always comes down to the lipo.
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Old Jan 11, 2013, 01:58 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
730 Posts
I completely agree and only fly by timer too, set for worst case scenarion full throttle for whole flight at 80% of capacity. Sometimes this means I come down with cells at 3.8v or slightly more.

I am still waiting for someone to invent a lightweight coulomb counter with a buzzer of flashing led to warn when a pre-set capacity has been reached. (I know DX8 and other high-end radios have this, I want to see a cheap standalone unit)
The problem with high LVC of 3.7V is that a high amp draw will often depress the voltage below this even from fully charged. In that case the LVC alarm would be set off too early.
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Old Jan 11, 2013, 02:09 AM
Has Sloped Off
dav3uk's Avatar
Uk South Wales
Joined Aug 2009
2,250 Posts
Some time ago I went through a phase in my prop planes of buying larger mah but lower C rating batteries, my logic was this a 2200 30C is 66a max out put but a 3000 20c is nearly there at 60a, the larger battery was in the first instance cheaper as 20c lipos seem unwanted.....and keeping the timer the same or there about I was leaving more % in the lipo. I never had any puff on me but..........my big conclusion was that most cheap to mid range lipo brand C ratings are overstated...they just cant deliver the numbers. So now when I buy lipos I always go a rating above what I need, so buy a 35c instead of 25c for instance.

That has resulted in me having only 1 puffed pack in the last 12 months and that was my fault as I ran it down to 3v in an application it wasnt designed for (was only a small 1000mah pack)

Keep the C rating up and as much Volts above the 3.3 as possible and your lipos will live much longer, and that save money in the long run........we all like that.

Dave
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Old Jan 11, 2013, 09:30 AM
Registered User
gooniac33's Avatar
Sunnyvale
Joined Feb 2009
4,961 Posts
Quote:
Originally Posted by The Don View Post
I have found puffing for me is a direct result of discharging too low. Just one instance of flying to LVC will result in the lipo puffing about 3-5 cycles later when used in an EDF application. If I happen to go below 3.5 volts/cell at rest then I am in dangerous territory. My ESC is set to its max of 3.3/cell and if I actually hit that and the ESC shuts off in flight, these new high C lipos will not rebound voltage like the old days. They will stay low about 3.3-3.4 not bounce back to 3.7 so if I hit LVC on and EDF in flight I know I toasted the lipo for EDF use. I typically mark the pack then use in a lower C application. If I keep using it in the EDF, the in about 3-5 flights later the pack will puff on me. I have not found any brand lipo that does not do this. So that is why I only fly by timer. I do not know why lipo manufactures do not suggest much higher LVC values these days. It is so easy to kill a lipo C rating by going below ~3.3 volts per cell. I get several emails a week from people who have 40C lipos and yet the ESC keeps hitting shutoff after one minute of flight time and they don't know why, or they get much lower watts than they should, and it always comes down to the lipo.
That is a valid point as well. And that can happen with a new battery that is being pushed too hard at the beginning. Voltage can drop really quickly with a new pack and drop below 3.5v way sooner than if it has been broken in. Another thing to note....if you store your batteries fully charged they can puff from that alone. And then when you fly them it will be even worse. My Sky Lipos have done this and I don't leave anything charged anymore...storage voltage.

Quote:
Originally Posted by green_flyer View Post
I completely agree and only fly by timer too, set for worst case scenarion full throttle for whole flight at 80% of capacity. Sometimes this means I come down with cells at 3.8v or slightly more.

I am still waiting for someone to invent a lightweight coulomb counter with a buzzer of flashing led to warn when a pre-set capacity has been reached. (I know DX8 and other high-end radios have this, I want to see a cheap standalone unit)
The problem with high LVC of 3.7V is that a high amp draw will often depress the voltage below this even from fully charged. In that case the LVC alarm would be set off too early.
I use my timer to remind me to land but sometimes you need to use common sense. If you use full throttle more than normal then you will need to land earlier as well. The timer can only do so much if you haven't set an accurate time limit. I always set my timers to suit my flying style and in most cases I land with 3.8v per cell but still mess up at times. And then adjust my timer to keep that from happening again...

Quote:
Originally Posted by dav3uk View Post
Some time ago I went through a phase in my prop planes of buying larger mah but lower C rating batteries, my logic was this a 2200 30C is 66a max out put but a 3000 20c is nearly there at 60a, the larger battery was in the first instance cheaper as 20c lipos seem unwanted.....and keeping the timer the same or there about I was leaving more % in the lipo. I never had any puff on me but..........my big conclusion was that most cheap to mid range lipo brand C ratings are overstated...they just cant deliver the numbers. So now when I buy lipos I always go a rating above what I need, so buy a 35c instead of 25c for instance.

That has resulted in me having only 1 puffed pack in the last 12 months and that was my fault as I ran it down to 3v in an application it wasnt designed for (was only a small 1000mah pack)

Keep the C rating up and as much Volts above the 3.3 as possible and your lipos will live much longer, and that save money in the long run........we all like that.

Dave
My magic number is 3.7v. I don't ever let it drop below that. The packs that I keep above that voltage last a lot longer.
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Old Jan 11, 2013, 02:17 PM
chuck
santa barbara, CA
Joined May 2009
3,941 Posts
Quote:
Originally Posted by voxel View Post
It's a bit OT, but these lipos were used on a Dynam Sbach which I didn't WOT much (2nd flight! too scared!)

My Turnigy 4s 850mah lipos for my Screamer are beginning to puff after a few runs. There's no airflow over it and I tend to WOT it in large 15-30 second chunks. A 25+ mpg gust flipped it over on the field table today and dented one of the vert stabs. Gah. It's survived all sorts of crazy grass landings and remain pristined and gets nicked up by this!!!? Oh well...
also , the realistic discharge that i believe these batteries can handle is no more than 20 c continuous. if u do the math on these dinky 850's it's 17 amps and i think thats pushing it . 30 sec chunks at over 20 amps are going to cook them, new , old or in between. all of mine have never been used like that and still show signs as they age .

chuck.
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Old Jan 11, 2013, 04:29 PM
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United States, FL, Altamonte Springs
Joined Jun 2012
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Originally Posted by chas650r View Post
also , the realistic discharge that i believe these batteries can handle is no more than 20 c continuous. if u do the math on these dinky 850's it's 17 amps and i think thats pushing it . 30 sec chunks at over 20 amps are going to cook them, new , old or in between. all of mine have never been used like that and still show signs as they age .

chuck.
Probably why the power drops off after half throttle. I think I can fit a 1000mah in the Screamer and have the CG perfect.

Had two more flights this afternoon in 15mph wind. When I landed they were barely warm so I'm throttle managing better. Also the puffing has reached a "steady-state" (not worse, not better).
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Old Jan 11, 2013, 06:21 PM
chuck
santa barbara, CA
Joined May 2009
3,941 Posts
ya, that is the issue w/ these small lipos, it's very easy to see 20 c discharge rate and they dont like it. if u think about it it's much less common to hit these # w/ the big lipos . a 4000 at 20 c is 80amps and 50 or 60 is most likely the amps u would see w/ a plane that would use 1 of this size.

the killer is the min voltage they see under load and although they may be at 3.8/cell at rest ,the under load voltage really drops on the small ones.

1 thing that i do to try to help this is to do my wfo passes early in the flight and tool around toward the end at less throttle.

chuck.
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Old Jan 12, 2013, 12:45 PM
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Mike20's Avatar
Joined Sep 2012
544 Posts
Maidened my Mig 15 today. She was really tail heavy with a 800mah battery on the first flight and after I moved the battery as far forward as I could it flew really well. Hopefully the new Gforce 1300mah packs will help out my cog.
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Old Jan 12, 2013, 01:20 PM
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Joe 1320's Avatar
United States, FL, Sebring
Joined Feb 2006
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Originally Posted by Mike20 View Post
Maidened my Mig 15 today. She was really tail heavy with a 800mah battery on the first flight and after I moved the battery as far forward as I could it flew really well. Hopefully the new Gforce 1300mah packs will help out my cog.
I use 1300s for the mig and it really settles down.
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Old Jan 12, 2013, 01:28 PM
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Joined Sep 2012
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Originally Posted by Joe 1320 View Post
I use 1300s for the mig and it really settles down.
Sweet deal. Can't wait. It flew really nice and quick once I moved the battery
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Old Jan 12, 2013, 03:08 PM
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Canada, AB, Edmonton
Joined Oct 2006
463 Posts
Does anyone have any experience with the V2 F-86 ( others) thatBanana Hobby sells. V2 has a gyro. Love to hear from anyone who's tried the gyro.
Thanks
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Old Jan 12, 2013, 09:17 PM
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United States, WA, Vancouver
Joined Mar 2012
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Originally Posted by trroadster View Post
Does anyone have any experience with the V2 F-86 ( others) thatBanana Hobby sells. V2 has a gyro. Love to hear from anyone who's tried the gyro.
Thanks
I bought a V2 F-86 ARF a month or so ago when they were on sale at BH for $65 and free shipping
I love it, have my gyro set to "pro" so I dont notice it much unless its breezy out, posted a video of the maiden several pages back: http://www.rcgroups.com/forums/showt...48808&page=159 scroll down the page you'll see it

Joe
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Old Jan 14, 2013, 12:12 AM
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United States, MI, Portage
Joined Nov 2012
128 Posts
I have the BH 50mm F-16 and F-22 w/ gyro. Beware: the BS2X that comes with the jets requires some pre-flight testing. The gyro in my F-16 had to be mounted upside down (with the gains and switches facing the bottom of the battery compartment) and in the regular direction (servo prongs facing the rear/tail). Use outdoor mounting tape or servo tape to mount the gyro to the bottom of the battery compartment. i've found that mounting the it near the front of the nose works the best.

The gyro in my F-22 installed normally (right side up), with the prongs pointing to the rear/tail. So, contrary to Pete's video, don't bother mounting the gyro sideways as he says to do. It won't correctly counter the pitch/roll of your plane. With that being said, the gyros ARE WELL WORTH GETTING. Another tip with setting up the gyros: MAKE SURE THE GYRO IS CONTROLLING THE AILERONS/ELEVONS IN THE CORRECT MANNER THAT COUNTER THE PLANE'S PITCH/ROLL!! Luckily, I caught this issue prior to flying my F-16. The gyros were countering the plane's roll correctly, but when I pitched the nose up, it moved the surfaces UP as well. And when I pitched the nose DOWN, the gyro moved the surfaces DOWN. There was absolutely no fix for this other than mounting the gyro upside down. Problem solved. The F-22's gyro did not have this problem, so I undoubtedly received an incorrectly manufactured gyro.

Both planes fly absolutely great. The gyro keeps both planes flying level in strong winds and make hand launching fool proof. So if your new to EDF jets or want to improve your hand launches, fly on windy days, etc. I highly recommend taking the time to correctly set up and install the gyros.

After flying these, I am amazed that people still buy the larger EDF's with more complicated builds, extensive electronics, junk retracts, etc. They definitely look cool and have slick features, but the bigger EDF's are slower, harder to operate (land) and limit yourself to certain flight venues.

For under $100, these are hard to beat.

Hope this post helps some of you, happy flying.
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Old Jan 14, 2013, 07:24 AM
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United States, AR, Jacksonville
Joined Jul 2004
395 Posts
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Originally Posted by bunkx9 View Post
After flying these, I am amazed that people still buy the larger EDF's with more complicated builds, extensive electronics, junk retracts, etc. They definitely look cool and have slick features, but the bigger EDF's are slower, harder to operate (land) and limit yourself to certain flight venues.
I used to think that way. Then I got tired of modifying Skyangel airframes to correct tail incidences and/or incorrect up/down thrust angles. But I'm sure the gyro can hide those flight characteristics quite well.

I'm currently focused on a Freewing Su-35. It requires alot of maintenance but it flys straight and true, no matter what power setting is put in.
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Old Jan 14, 2013, 09:01 AM
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United States, FL, Altamonte Springs
Joined Jun 2012
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Originally Posted by Whiskey Whiskey View Post
I used to think that way. Then I got tired of modifying Skyangel airframes to correct tail incidences and/or incorrect up/down thrust angles. But I'm sure the gyro can hide those flight characteristics quite well.

I'm currently focused on a Freewing Su-35. It requires alot of maintenance but it flys straight and true, no matter what power setting is put in.
That's my view of the SkyAngels (had the Mig15, F16, F18, Katana - which all had warped surfaces due to shipping or poor landings) until the Screamer. Screamer is a no fuss jet. It's a solid piece of foam with only glue on vert stabs. Stick a 4s motor on that and it's a blast. Also had a big battery compartment compare to the F16 and Mig15.
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