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Old Jan 21, 2013, 10:18 AM
Intermediate boob
demuddy's Avatar
Seoul, Korea
Joined Nov 2009
429 Posts
Careful!
My plane caught on fire in flight!! Lets NTSB this weird event.

My plane caught on fire while in the air! (No relation to the Dreamliners now days grounded for similar Lipo fires/problems, at least I don't think so).

As you can see, a PZ T-28 Trojan, with an E-Flite Power 10 motor, E-Flite 3S 2200 mAh Lipo, E-Flite 40A ESC, and stock T-28 prop (E 9.5 x 7.5). I took her up, winged around out of the ROG, and suddenly lost power and had difficulty getting lift. I tried to do an emergency landing flying downwind (I didn't have enough airspeed to attempt a turn into the wind and risk a tip stall), but had too much altitude and overshot the runway. I had bled off enough speed/energy making a few elevator dips and pulls when I had committed to coming in and had bumped into a tree trunk to a stop.

When it passed me downwind, I saw that the prop had come off (I swear on my receding hairline that I had tightened that fella good, but errors are made), and cursed under my breath. I saw a strange smoke coming out of the aft fuselage under-vent holes (stock fuselage configuration). When I got there, the lipo had ejected from the fuse and was on dry grass burning, on fire. I covered the lipo in snow, my wingman took the picture, and I ran for the fire-extinguisher in my bag, but the fire was out already.

The fuselage bubbled and puffy as in the picture shows me that the Lipo was giving off heat during flight, since the Lipo had ejected on impact during the emergency landing (Nothing was damaged, other than the second cowl I had glued onto the screwed on cowl had been knocked off, although the inner cowl had stayed on and undamaged--habit of doubling up on cowls nested inside each other from noticing I go through a lot of cowls).

I haven't tested the ESC, receiver, or motor yet, thinking I might make something worse or cause another fire.

Some of the others at the club think it might have been a short. I used a deans-to-EC3 connector changer that I soldered together to go from my ESC because all of my 4S Lipos are deans, and I had recently switched out a bigger motor to a Power 10 now installed. Another factor: To be honest, I had fast charged my 3S Lipos from my iMAX B6 QUATTRO Multi Charger & Balancer, even though I knew that one of the Lipos didnít take charge at full capacity anymore when balance charging (it stops charging at 12.4 V, and doesn't make it to 12.6 V anymore).

Was it a short? Was it my stupid overcharging? Assuming that the heat didnít melt the Rx and ESC and motor, are they ok to test? I'm figuring the ESC is most likely to fry if I had an electrical short or other issue. The prop coming off may have caused the esc to overload (I probably had gunned the throttle at one point to regain lift before I realized that the prop was off), but past 40A on the stock prop?!

In short, what happened? Anyway, too, Gaa! I have never seen or heard tell of a Lipo fire in flight. Has anyone else?
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Old Jan 21, 2013, 10:55 AM
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DustBen's Avatar
United States, NE, Kearney
Joined Dec 2011
2,232 Posts
Quote:
Originally Posted by demuddy View Post
My plane caught on fire while in the air! (No relation to the Dreamliners now days grounded for similar Lipo fires/problems, at least I don't think so).


Was it a short? Was it my stupid overcharging? Assuming that the heat didnít melt the Rx and ESC and motor, are they ok to test? I'm figuring the ESC is most likely to fry if I had an electrical short or other issue. The prop coming off may have caused the esc to overload (I probably had gunned the throttle at one point to regain lift before I realized that the prop was off), but past 40A on the stock prop?!

In short, what happened? Anyway, too, Gaa! I have never seen or heard tell of a Lipo fire in flight. Has anyone else?
Your highlighted quote speaks volumes.
Stupid over-charging Lipos is asking for trouble.
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Old Jan 21, 2013, 10:58 AM
Registered User
United States, ID, Burley
Joined Mar 2012
3,282 Posts
my GUESS is a bad solder joint on the deans to your other plug adapter. a bad joint will create heat . but it is usually the esc that goes poof first ?
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Old Jan 21, 2013, 11:00 AM
I eat glue
Canada, NS, Yarmouth
Joined Jul 2006
3,416 Posts
I vote for the charging too. I've only had one lipo puff, because of my hooking it up backwards! Switched connectors after that.
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Old Jan 21, 2013, 11:02 AM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,284 Posts
It was likely that tired lipo that was trying to tell you that it was tired and didn't want to balance anymore committing suicide. Internal short and *poof*.

mw
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Old Jan 21, 2013, 11:10 AM
Arizona Fun
Casa Grande Arizona
Joined Mar 2010
303 Posts
Bummer...

Sorry about your loss. I will never 'fast charge' a lipo even though a few here insist it is ok to do so. If you flew soon after your fast charge, then that lipo may have been warm already and flying caused to much heat?
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Old Jan 21, 2013, 11:24 AM
Snappy Title On Backorder....
tsymonds's Avatar
United States, TX, Killeen
Joined Jun 2011
1,058 Posts
What Eflite pack is it? 20c or 30c? Either way your pulling 20+c from the pack and if the pack is tired with high IR then the result will likely be what you experienced. The other issue is that on a full pack your pulling over 40amps. Might want to rethink your power setup.
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Old Jan 21, 2013, 11:51 AM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,848 Posts
There is nothing wrong with fast charging.

Fast charging vs regular charging at the same C-rate is in fact a good practice. Fast charging by using a much higher C-rate is another issue. I'm referring here about using the "Fast Charge" function on the charger.

The only difference between "fast charging" and regular charging is that the charger turns off sooner, eliminating the long period the charger spends trying to get the last few mah's into the pack. Fast charging in fact will prolong the life of your batteries.

Look at this charging graph. Note the time it takes to charge once the pack reaches the 4.2V cell voltage at which time the current starts to drop. What the fast charge function does is stop the charge once the current reaches say 200ma instead of 50ma as shown in this graph. About a 20 min shorter charge time is obtained by doing this. You might loose 2-3% of pack capacity by doing this but it makes for a lot more cycles.
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Old Jan 21, 2013, 11:57 AM
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DustBen's Avatar
United States, NE, Kearney
Joined Dec 2011
2,232 Posts
Quote:
Originally Posted by hoppy View Post
There is nothing wrong with fast charging.

Fast charging vs regular charging at the same C-rate is in fact a good practice. Fast charging by using a much higher C-rate is another issue. I'm referring here about using the "Fast Charge" function on the charger.

The only difference between "fast charging" and regular charging is that the charger turns off sooner, eliminating the long period the charger spends trying to get the last few mah's into the pack. Fast charging in fact will prolong the life of your batteries.

Look at this charging graph. Note the time it takes to charge once the pack reaches the 4.2V cell voltage at which time the current starts to drop. What the fast charge function does is stop the charge once the current reaches say 200ma instead of 50ma as shown in this graph. About a 20 min shorter charge time is obtained by doing this. You might loose 2-3% of pack capacity by doing this but it makes for a lot more cycles.
We discharge a pack in an 8 minute flight... doesn't it stand to reason it should be charged at the same rate? I know this is against ALL we are told and learn, but... what am I missing?
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Old Jan 21, 2013, 12:28 PM
aka: A.Roger Wilfong
gnofliwr's Avatar
Novi, Michigan, United States
Joined Jan 2001
2,515 Posts
I've never used this charger, but from the on-line manual, it appears that the "fast charge" mode does not use the balance leads, but charges directly through the power leads and judges the state if charge based on the terminal voltage of the entire pack. That being the case, if you had a cell weak enough to trip the protection circuit when doing a balance charge, the weak cell was probably the cause of the problem. It must have really been weak, since SkyRC's spec for fast charging a LiPo is 1C (not really all that fast).
Quote:
WARNINGS AND SAFETY NOTES
...
LiPo Voltage level: 3.7V/cell
Max. charge voltage: 4.2V/cell
Allowable fast charge current: 1C or less

- Manual, page 6.
This shouldn't have been fast enough to cause a problem with a slightly weak cell.

With respect to "fast charging"; it's never goo d to exceed the battery manufacturer's specs for charging. With high C batteries, that have low internal resistance, you can get away with charging at higher the 1C. This will shorten the phase 1, constant current phase of LiPo charging. As long as the charge rate isn't high enough to cause internal heating caused by the internal resistance, you don't need to worry. This will get you to the 80% point sooner, but if you still want that last bit put in by the phase 2, constant voltage phase of the charge, you're stck with waiting the full time for that phase - going faster is inviting a "thermal event".

With respect to life, slower is always better it generates less heat - which is the bane of batteries. Or maybe they just seem to last longer because you spend so much time waiting for them to charge.

- Roger
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Old Jan 21, 2013, 12:42 PM
Senile Member
Lnagel's Avatar
Moab, Utah, USA
Joined Apr 2003
5,878 Posts
Quote:
Originally Posted by demuddy View Post
...even though I knew that one of the Lipos didnít take charge at full capacity anymore when balance charging (it stops charging at 12.4 V, and doesn't make it to 12.6 V anymore).
Did that happen to be the battery that was in the plane at the time the incident occured? If so, that could explain a lot.

Larry
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Old Jan 21, 2013, 12:43 PM
Intermediate boob
demuddy's Avatar
Seoul, Korea
Joined Nov 2009
429 Posts
Doing this on my cell so forgive my not responding to each by name to commensurate point.

More info #1: 30 C Lipo
Correction #1: 60 A esc
Confession #1: For some stupid reason that day, and against my better judgement, though lack of actual experience against said stupidity--of this specific act of massive stupidity, I not only fast charged but also turned off and turned back on the fast charge cycle...ahem...three times, to get my pretty numbers on that pretty display to 4.2 V per cell.
Prediction #1: Here comes the flame. Did I tell you that I did massive stupidity that day? (Now I know what those poor blokes who caused real jetliner accidents feel when they had miracalously survived their stupidity and are thereafter under NTSB investigation). Please, go easy on the punishment and more info on the "crime"?

Observation #1: I notice in the post burn pic that the wire out of the lipo batt is burned from the stem to the EC3 joint, which makes me agree that it was an internal short? Someone sign off please if this is a reasonable deduction?

More info #2: I had used these joint changers for a while with my Watts Up watt meter. And the batts I've had for a while too although I'm guessing under 50 cycles. So, maybe it wasn't a short at the joints? Although I agree something could always have come loose or made a gap exposing bare wire. I don't consider myself an experienced welder, for example.

Never gonna force charge a lipo ever again, phew! My wife would not be kind to my burning down our house, over my burning one of my "man toys." ( I have since had PTSD chills waking from a sleep worried I've not safely stored my, prolly $1000+, stash of lipos)
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Old Jan 21, 2013, 04:59 PM
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aurorae's Avatar
Joined Sep 2008
675 Posts
Quote:
Originally Posted by Lnagel View Post
Did that happen to be the battery that was in the plane at the time the incident occured? If so, that could explain a lot.

Larry
This is what I was thinking. You have a Lipo that will no longer fully charge, that sounds like it has a bad cell.
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Old Jan 21, 2013, 06:48 PM
rookie
wilf370's Avatar
Canada, SK, Saskatoon
Joined Dec 2012
546 Posts
You sure it wasn't one of them dang North Korean ICBN's!!!!!
Just Jokes Wilf
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Old Jan 21, 2013, 07:07 PM
Radian +2.4Ghz FPV = way to go
Canada, BC, Richmond
Joined Dec 2012
368 Posts
had this happen to me. threw the plane, went down, I kept the motor running and poof, it caught fire. I beleive just like in my case, the esc may have been the source of trouble
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