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Old Jul 03, 2012, 02:49 PM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,032 Posts
I'll be interested to hear how your 19.5" version fly's. My 16.5" mini was a hoot with a very rapid roll rate. I only used a 450 3s pack & 20 gram 2000 kv motor so a bit lighter than your set up. Sadly nothing left of it as it was hanging up right in front of the 800 deg lipo fire that took the majority of my 20+ models & equipment.
A video would be great if you can manage it. Just run on 50% rates and lots of expo until you get the feel of it.
Andy
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Old Jul 04, 2012, 12:14 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Quote:
Originally Posted by headlessagain View Post
I'll be interested to hear how your 19.5" version fly's. My 16.5" mini was a hoot with a very rapid roll rate. I only used a 450 3s pack & 20 gram 2000 kv motor so a bit lighter than your set up. Sadly nothing left of it as it was hanging up right in front of the 800 deg lipo fire that took the majority of my 20+ models & equipment.
A video would be great if you can manage it. Just run on 50% rates and lots of expo until you get the feel of it.
Andy
what?am I understanding you correctly?you had a lipo go awoll and burnt all you planes?Sorry to hear
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Old Jul 04, 2012, 12:31 AM
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United States, OH, Eaton
Joined May 2006
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Quote:
Originally Posted by headlessagain View Post
I'll be interested to hear how your 19.5" version fly's. My 16.5" mini was a hoot with a very rapid roll rate. I only used a 450 3s pack & 20 gram 2000 kv motor so a bit lighter than your set up. Sadly nothing left of it as it was hanging up right in front of the 800 deg lipo fire that took the majority of my 20+ models & equipment.
A video would be great if you can manage it. Just run on 50% rates and lots of expo until you get the feel of it.
Andy
So sorry to hear that. What caused the lipo to go or do you have a separate thread on that somewhere?
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Old Jul 04, 2012, 01:03 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,032 Posts
Here is the initial post in this thread
http://www.rcgroups.com/forums/showthread.php?t=1662585
"Last Sunday I lost 20+ planes to a lipo fire in my integral garage. I only ever charge at 1c and I was only balance charging two smaller packs (850 3s and 1050 3s) Both lipos were in good condition but I made the mistake of leaving them on their own for 20 mins and had them sitting on a plastic shelf. Yeah, I know, real dumb. Even dumber was fighting the fire with a hose after the 1 & 2 kg dry powder jobbies had been exhausted. See the fire was raging in between the gas main/meter on one side and the incoming mains electric supply on the other. Got it out by the time Fireman Sam arrived who were not happy I was in there. However, I reckon if I hadn't, both my house and my neighbours would have been taken out in a gas explosion. The gas pipe is meant to be protected by foam pumped between it and the outer metal tube but the dumb a** contractor who changed the meter a few years ago skipped that part.
The tangled chunk of plastic racking,storage boxes, spare motors,ESC's, props and 360 to 1550 mAh lipos were left on the drive as I didn't want to risk another fire. I was right to be cautious as on Wednesday morning at 4:45 the pile self ignited with flames shooting 6' into the air. I used both my new 2kg fire extinguishers to put it out and Fireman Sam played his hose around for a while until they were happy.
So rest in peace MPX Blizzard, HK RareBear,Phoenix 2000,Parkzone F4F, GWS Me262 & FW190, Freeair Fokker D VII & Mitchell, Phase 3 F-16, Graupner Tiger Shark, FMS P-47 and all my scratch built foamies. Also toasted my DX7, an old Futaba 35 mHz TX, 2 cordless drills, a heat gun and pistol soldering iron.(non RC claim is just under 1000!)
The moral of this sad story is NEVER leave your lipos unattended for even a minute and ALWAYS charge in a lipo bag on a non flammable surface. Keep your charging area free of any of your other precious RC stuff. The list for the loss adjuster is going to be quite a long one if I can remember all of my spares".
Posted in full as a warning to anybody who might be becoming complacent about lipo's
I met a car and boat RC guy last week who often charges his unattended 4500-5000 mAh 2S packs in the boot of his new car!
Andy
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Old Jul 04, 2012, 01:14 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
1,328 Posts
so far ive been really lucky. Ive only had 1 li-ion pack go bad from a bad charger. It being Li-ion cylindricle cells it just got really hot, hot enough to melt the heat shrink.

Just to be safe though I now have a battery bunker I made from an old Ford Explorer amp that went bad. Cut the thing down in half and made a hinged bottom. Its all aluminum with enough gaps to keep it from over preasureing and exploding. Charger sits outside while the battery has its charge lead go out through a small notch I cut.
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Old Jul 04, 2012, 01:56 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
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Headless.sorry to hear about this disaster.but your mistake was charging 2 batteries of different capacities...when charging more than one battery at once the charger "thinks" it's one battery.therefor one has to charge batts of the same capacity so that the amperage that gets "put in" by the charger is evenly distributed into the batts.So what you are saying is that you were charging at 1.9A,if at 1C?that would be the combined capacity of the 2 lipo's,how ever you were putting 950mah into each,do you know what the charge rate of the 850 was?if it was only 1C,then that's the cause,it cooked and said hello....just my $0.02
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Old Jul 04, 2012, 02:05 PM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,032 Posts
Quote:
Originally Posted by chop stiX View Post
Headless.sorry to hear about this disaster.but your mistake was charging 2 batteries of different capacities...when charging more than one battery at once the charger "thinks" it's one battery.therefor one has to charge batts of the same capacity so that the amperage that gets "put in" by the charger is evenly distributed into the batts.So what you are saying is that you were charging at 1.9A,if at 1C?that would be the combined capacity of the 2 lipo's,how ever you were putting 950mah into each,do you know what the charge rate of the 850 was?if it was only 1C,then that's the cause,it cooked and said hello....just my $0.02
I have (had!) 4 balance chargers which were fed through a individually switched G T Power Multi Distributor http://www.4-max.co.uk/gt-power-distribution-box.htm so each lipo had it's own dedicated charger. Even though some of my lipo's were rated at 5c charge rate, I never charged at more than 1c. If only it was that simple!
Andy
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Old Jul 04, 2012, 07:24 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
1,328 Posts
Now you guys have done it. I spent all night worried about my li-pos Like Ive said, Ive only ever had one go bad on a charger, and to be honest, it was a charger I made as an electronics hobby and had something wrong on the board.

So today while i was at my local hardware store, I asked if they had any small metal boxes. After some disscusion between the employees who first thought of the long, narrow tool boxes, one remembered they also had a small cash lock box, and its fire rated! Not bad for $15. tons of room in the thing. Going to make a sheet rock tray to hold the batteries, and still have room for my chargeing bunker and charger.

On a side note I did try to fly my mini, but quickly found that my motor firewall wasnt strong enough as it came off after a couple test throws
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Old Jul 05, 2012, 12:13 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Quote:
Originally Posted by headlessagain View Post
I have (had!) 4 balance chargers which were fed through a individually switched G T Power Multi Distributor http://www.4-max.co.uk/gt-power-distribution-box.htm so each lipo had it's own dedicated charger. Even though some of my lipo's were rated at 5c charge rate, I never charged at more than 1c. If only it was that simple!
Andy
Hi Andy
I understand.so in all it's just unlucky.jees I would really be unhappy if that had to happen to me,but in the light of it,it's only a few planes,could've been worse...
I must admit I sometimes leave my batts unattended when I charge and pop out to the shops while they are charging.no more of that after this story.
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Old Jul 05, 2012, 01:03 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
1,328 Posts
be glad it was just your hobby (oh no, you have an excuse to make new planes, darn ) and not the entire house.

now you have a chance to rethink somethings and make everrything beter, provided your wife lets you bring that crazy stuff back in the house . Perhaps look into a metal cabinet lined with sheet rock, or some other fire proof material, for chargeing the batteries in for the future.
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Old Jul 05, 2012, 01:05 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,032 Posts
It could have been much worse as some gas had leaked into the next door loft via the shared cavity wall. If I hadn't tackled the fire we could have lost the house
I looked at fire proof boxes and small safes but concluded that, as they are designed to stop fire from damaging the contents stored inside, they won't really work if a lipo inside goes bad. There is also the risk of them exploding when each cell vents. Just search for tests using sealed ammo boxes!
I've built my charging station out of concrete blocks and fire proof plasterboard (1200 degs rated) with five coloured coded bays for each lipo that will be charged in a lipo sacks. The power supply will go in a lower bay with the quad and single charger on the top shelf.

Andy
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Old Jul 05, 2012, 02:22 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
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I think maybe I should look into something like this.I charge on my "charging desk"which is just an extra laminated wooden desk I have
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Old Jul 05, 2012, 02:46 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
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the box I got isnt sealed like ammo boxes. It has several small openings and the lid isnt sealed. No seal means preasure can escape. there is some air flow but not enough for letting a huge amount of air in to feed the fire.

I did look up several tests last night. Also, I grew up in auto repair shops and learned a lot from my Dad in regaurds to what is needed to contain batteries should they blow. He has had to carry coworkers to the showers after they accidently put wrenches down across battery leads on a car. Wrenches tend to weld to battery terminals very fast, followed by exploding batteries shortly after.

Also, not sure if you have ever seen them, but they make special lids for shop garbage cans that are open on the top, but the narrow opening of the lid keeps a large amount of air from flowing in, and keep the smoke more or less in the can to help smother the fire, should oily rags be ignited.

The vents in my little box do the same thing. they keep the box from over preasureing, but keep the smoke in to help smother the fire. I just have to remember to NOT open the thing should one go off
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Old Jul 11, 2012, 03:54 PM
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Joined Apr 2011
20 Posts
Hey guys... question for ya.

I have a S-1804 Scorpion Motor, it's a 1650kv motor recommended prop is 8x4 and it's a 6.4v 3.2A (5900 RPM) motor... but it puts out 150g of thrust. I was thinking due to it being a 1650kv motor this might work for my funbat. I needed a new motor on our funbat and had this... anyone have any thoughts on this motor? The KV sounds more than right for for some reason the thrust is throwing me off here for some reason? is that enough thrust?

Just curious?
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Old Jul 11, 2012, 04:24 PM
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United States, OH, Eaton
Joined May 2006
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Quote:
Originally Posted by mvaller00 View Post
Hey guys... question for ya.

I have a S-1804 Scorpion Motor, it's a 1650kv motor recommended prop is 8x4 and it's a 6.4v 3.2A (5900 RPM) motor... but it puts out 150g of thrust. I was thinking due to it being a 1650kv motor this might work for my funbat. I needed a new motor on our funbat and had this... anyone have any thoughts on this motor? The KV sounds more than right for for some reason the thrust is throwing me off here for some reason? is that enough thrust?

Just curious?
The full size Funbat needs a bigger motor than that. As your motor size increases, the plane's weight and thrust also increase. When the thrust exceeds the total weight of the plane, that's where the fun begins. My thrust to weight ratio is nearly 2 to 1. If your plane will balance and is lightweight a 24g motor is fine but I wouldn't go any smaller.
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