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Old Oct 04, 2011, 05:37 PM
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Loosecannon Elmo's Avatar
United States, CA, Orange
Joined Oct 2011
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Quote:
Originally Posted by jfetter View Post
Just get a good battery?! I've been flying with the Thunder Power G6 4,400 mAh 65C packs for weeks, no issues...


Jack
I definitely thought about it but I gotta buy more batteries and I don't wanna spend anything. This new setup I can do for free because I have 5 useable 6s packs.

Quote:
Originally Posted by schiwo1 View Post
Hmm, when your 4s puffs up, you are using either old batteries or a pack with insufficient C-rate. At the amps the motors pull, you need a 45C continuous load pack. Also, you should pre-heat the pack to ~40Deg Celsius prior to flying.

Let me know how the 6s setup works. My guess is 10% more flight time. Thats what you would get with a 4400 4s pack at the same or even less weight as the 6s setup.
Best



Stephan
Haha yeah they are kinda old and it's only a 25c 4000mah. I will definitely let you know.

Quote:
Originally Posted by jfetter View Post
6 more ounces on the nose might be an issue as well, CG is tough with extra battery...

Jack
Already took that into account. I had to do a little surgery but the cg will be the same as where it was before.
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Old Oct 04, 2011, 06:10 PM
Drinks Day Old Expired Milk
VooDoo Child's Avatar
United States, OR, Portland
Joined Aug 2010
2,832 Posts
Quote:
Originally Posted by Loosecannon Elmo View Post
Hey everybody. I've been reading this thread for a little while now and I ended up buying mine a couple weeks ago. So far I have ten flights on it and I love it. The main problem I've been having though is my batteries can't keep up with the power that the motors want and I can't go full throttle. They also puff up pretty bad after the 4 min. flight. So I've decided to try an experiment.

My dad has some extra motors from his lx models that he's been flying so I've decided to convert mine to a 6 cell setup. With the seb art fans and the lx motors, each motor puts out about 1600g of thrust @48a which is about 300-400g more thrust per motor than the stock seb art motors do (with the 4 cell pack that I have), and the only weight difference is the 6 cell battery being about 170g heavier.

So in the end I'm hoping to get some more power and longer flight times with the new set up. I should be done by tomorrow and I should get to testing it this weekend for those who care. I'll let you know how it goes.
It was just a matter of time before somebody had to Hop One Up Can you post some pics of your conversion ??? You have my attention.
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Old Oct 05, 2011, 12:11 AM
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Quote:
Originally Posted by Loosecannon Elmo View Post
Haha yeah they are kinda old and it's only a 25c 4000mah.
That explains. Its like driving a car with parking brakes on
Hope your 6s are better otherwise the result wont be what you expect.
Best Stephan
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Old Oct 05, 2011, 11:01 AM
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USA, GA, Atlanta
Joined Nov 2008
14,387 Posts
I have found that no matter what size fan I fly, if I am running anything less than a good 35+c pack; it will no doubt swell.

I prefer the 45/90c Turnigey nano's for the price and for their ability to quick charge at 22.2amps.
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Old Oct 05, 2011, 04:14 PM
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Loosecannon Elmo's Avatar
United States, CA, Orange
Joined Oct 2011
6 Posts
Unfortunately I don't have any good batteries that are light enough but I have some rough specs about the setup with a 20c 4000mah 6s. Peak watts is about 1700, max amperage is 80a, my cg is about 128mm from the leading edge of the wing, and the auw is 1963g. Here's some pics. of the conversion also. It's not pretty but it works ok. I basically just cut foam out and glued some balsa wood blocks in to keep it from moving around.
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Last edited by Loosecannon Elmo; Oct 05, 2011 at 11:44 PM. Reason: Thrust wasn't accurate
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Old Oct 05, 2011, 04:18 PM
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ATCDave's Avatar
United States, NH, Rindge
Joined Feb 2006
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Pre-heating packs

Quote:
Originally Posted by schiwo1 View Post
Hmm, when your 4s puffs up, you are using either old batteries or a pack with insufficient C-rate. At the amps the motors pull, you need a 45C continuous load pack. Also, you should pre-heat the pack to ~40Deg Celsius prior to flying.
Best
Stephan
Hey Stephan,

I've heard you mention a couple of times now about pre-heating the packs. This is a new concept to me. Would you mind elaborating a little bit about this?

I'm curious because besides flying this MIG, I am beginning to delve into higher current helicopter set-ups as well. Thank you sir!

Best Regards,

Dave
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Old Oct 05, 2011, 04:35 PM
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fredmdbud's Avatar
USA, MD, Frederick
Joined Jan 2010
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Quote:
Originally Posted by ATCDave View Post
Hey Stephan,

I've heard you mention a couple of times now about pre-heating the packs. This is a new concept to me. Would you mind elaborating a little bit about this?

I'm curious because besides flying this MIG, I am beginning to delve into higher current helicopter set-ups as well. Thank you sir!

Best Regards,

Dave
Like all chemical reactions, temperature has an effect on reaction rate. LiPo current delivery capacity drops with lower temperature. Pre-heating batteries is like "priming the pump", getting the battery close to its ideal operating temperature.
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Old Oct 05, 2011, 05:22 PM
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Joined Nov 2009
429 Posts
Dave,
Lipos have their lowest internal resistance at temperatures around 40 deg C.
The lower the resistance, the more Amps at the same Voltage level you can pull.
The difference to a room temperature pack can be very significant when it comes to high loads (means >100A in case of the Mig) Example:
4000 4s Nanotech in theMig during taksoff ~115A at room temp, close to 135A (>2KW input power!) when heated to 40deg.

Another side benefit: a cold battery, due to the higher internal resistance, usually heats up quickly under high Amp load. Due to the lack of airflow, the inner cells of a pack become warmer than the outer cells, eventually resulting in a shortened battery life.
Pre heating helps to avoid this effect, and the pack will last longer.
Caution: more is not better - if temp crosses the 50 deg Celsius mark you may destroy the battery.
Also, this method will not make an old battery better.
At lower currents, preheating will not make much of a difference.
You find plenty of battery heating equipment at virtually every shop.
Best Stephan
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Last edited by schiwo1; Oct 05, 2011 at 05:28 PM.
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Old Oct 05, 2011, 08:07 PM
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jfetter's Avatar
Miramar, Florida
Joined Jul 2007
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Quote:
Originally Posted by ATCDave View Post
I've heard you mention a couple of times now about pre-heating the packs. This is a new concept to me. Would you mind elaborating a little bit about this?
You shouldn't need to do this with a good pack, this is something they do in competition and heat is enemy number one with LiPo's...

Jack
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Old Oct 05, 2011, 08:24 PM
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Canada
Joined Jul 2009
6,459 Posts
How do you pre-heat something to 40C just before you fly? Even if you stuff it in your armpit, it'll only get up to 37C. I don't know. Seems a little compulsive/obsessive with a little anal retentiveness thrown in.
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Old Oct 05, 2011, 08:25 PM
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VooDoo Child's Avatar
United States, OR, Portland
Joined Aug 2010
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I went out of town for 5 days to be in a friends wedding (poor guy) So it has been a while since i flew the Mig (week and a half) When i got back we had nothing but 20mph winds....So after two days of no flying since coming home,i decided to try the Mig in HIGH WINDS ( most i have flown it in was around 12mph) we had 20mph winds with gusts up to 25 today....I was very suprised how well it did,do not get me wrong,it does float around alot,but easy to handle if you keep your head in the game......I took a crappy video,so here it is.... http://www.youtube.com/user/voodoo12667
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Old Oct 06, 2011, 12:10 AM
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Joined Nov 2009
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Quote:
Originally Posted by xviper View Post
How do you pre-heat something to 40C just before you fly? Even if you stuff it in your armpit, it'll only get up to 37C. I don't know. Seems a little compulsive/obsessive with a little anal retentiveness thrown in.
Its getting OT, but here is one example how you do it:
http://www.rcgroups.com/forums/showthread.php?t=1459652

Preheating is not *necessary* but provides you with better performance and an extended battery life when it comes to high peak loads.
Now back to the Mig
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Old Oct 06, 2011, 05:56 AM
"Aircraftus Fragmentum"
kydawg1's Avatar
Motor City USA
Joined Mar 2007
3,613 Posts
As the months get cooler here in Mo Town....we place our packs into a Peltier Heated Cooler (you know the Thermoelectric travel hot / cold coolers that you plug in). I bought a $60 one from Amazon, added banana plugs and hook it up to my RC Charging Spare Car Battery. Inside the cooler I added a small squirrel fan that moves heat off the heatsink and stirs up the warm air inside. After about 20 minutes the packs are maybe 95 - 100 deg F (getting close to 40 deg C). Works like a charm since I do not keep my car running during the 4-6 hour long fall/winter flying sessions.

This is the one I bought.

http://www.amazon.com/gp/product/B0001MQ7DG
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Old Oct 06, 2011, 07:39 AM
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sanman55's Avatar
powder springs georgia
Joined Nov 2003
2,010 Posts
Quote:
Originally Posted by xviper View Post
How do you pre-heat something to 40C just before you fly? Even if you stuff it in your armpit, it'll only get up to 37C. I don't know. Seems a little compulsive/obsessive with a little anal retentiveness thrown in.
Thats getting very testicle
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Old Oct 06, 2011, 07:50 AM
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sanman55's Avatar
powder springs georgia
Joined Nov 2003
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Quote:
Originally Posted by VooDoo Child View Post
I went out of town for 5 days to be in a friends wedding (poor guy) So it has been a while since i flew the Mig (week and a half) When i got back we had nothing but 20mph winds....So after two days of no flying since coming home,i decided to try the Mig in HIGH WINDS ( most i have flown it in was around 12mph) we had 20mph winds with gusts up to 25 today....I was very suprised how well it did,do not get me wrong,it does float around alot,but easy to handle if you keep your head in the game......I took a crappy video,so here it is.... http://www.youtube.com/user/voodoo12667
BEAUTIFUL FLIGHT... Man you are getting good..that was some close hovering ..but 25mph...I did not even see the trees moving in the back ground..In your hover it should have been moving backwards...fast.... maybe the winds aloft were heavy..I could not tell...Please don't get mad at my questioning the mph.. Love your input but I would need to see a flag or wind meter or something...
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