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Old Jan 17, 2005, 11:12 PM
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Sunnyvale Ca
Joined Jun 2002
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"safety Nazi" goes before LiPoly firing line!

LiPoly users,
Crazy Ted – a.k.a. the 'safety Nazi' -- has been taken to the LiPoly "fire"ing line.

Just when you think you are a "safe player" you let down your guard. Last night I had two failures: one mental and one electronic.

I had a newly delivered single cell of roughly 1100 maH that I was testing to see if it could be “revived”. It came to the house at 1.2 volts when I got it and I had done the 10 minute “boost up” at 1/10 C to see if it would come above 3 volts DC. It passed with flying colors. The next step is to bring it up to full 4.2 volts at roughly 1/5 to C in a slow controlled manner. I then join all the packs of that type together and then cycle them several times at a 1C discharge rate and a .7C charge rate. If all those cycles go well, then the pack is ready for a “flying test”. Even then it will have to go for 5 more identical cycles before I will consider the pack “safe”.

So I was charging this 1100 maH cell up to the 4.2 volt charge. I had the new 18VDC at 3 amp power supply that has been discussed on this forum. I had used it three or four times to charge known good packs and it performed well as a CV/CC power supply. The only shortcoming that the new power supply has is that the voltage control is rather twitchy to set to 4.2 volts (the last digit is hard to set easily by single digit moves).

FIRST FAILURE:
I put the cell in my corningware 4” deep dish and went into the house to check my email. I got several phone calls and a few other distractions. It was 11:30PM and I went to bed. I normally always go to the garage to check that everything is off and everything is secure. I forgot this time.

The next morning before work, I went through the garage to my car. I saw the light on the power supply was on. I then saw that the cell had caught fire, spun several times in the corningware dish, and charred the AC line cords that just happened to be near the dish. There were tiny metal shards everywhere in a 2.5 foot radius of the dish. There were paper towels nearby and newspaper that the dish was on. They had all been “singed” by the metal shards. I had forgotten to shut done the supply and a fire had broken out during the night. I had just forgotten to follow my own rules about carrying a timer with me when I go into the house for a few minutes. I had forgotten to check the garage before retiring for the evening. All my good habits had been forgotten for just one occasion. It was just being sloppy.

I tested the garage’s smoke detector and it was working. Apparently the fire did not set it off…..but I find it hard to believe it did not make enough smoke to set it off. Regardless, my wife and I did not hear it. My two kids were spending the night at friends and so no one was on the first floor who would have heard the much louder signal.

SECOND FAILURE: I checked the power supply that morning. The voltage had now crept up to 5.4 volts DC. I know it was set to 4.2 VDC the night before. Something (temperature, resistor failure, start-up drift) had made the voltage increase. But 5.4 volts on a cell should not normally make it go “vent and flame”. The current was set at 40mamps. I am really amazed that that combination went to “vent and flame”. It could be this was a characteristic of the “low voltage brand new cell” but it had returned to 3.0 volts/cell with no problem. At any rate, I have no clue why the voltage from the power supply went up and why the cell caught fire. I will do very through checks on that power supply before it gets used again.

The only thing that prevented the house from burning down was the fact that I used the corningware dish. It is clear that the cell did the “rocket number” and spun around the dish at high velocity (how do I know? The clip leads were thrown clear by a strong force). I will also keep all flammable materials much farther away (I normally use an aluminum plate to rest the Corningware dish upon, but it had been moved on this occasion. Needless to say it will ALWAYS be there from now on.

THINGS LEARNED:
1) stay nearby
2) use a timer if you walk away for even 2 minutes
3) Put the sand bag on top of the cell (I had one sitting there and did not place it on because I was using the tiny push-clips and the bag might have disconnected them). Poor judgement call.
4) Put a mechanical power timer on your voltage source that kills the AC power when 15 minutes have elapsed if not manually reset.
5) Put a second fire detector on the ceiling of the garage right over the workbench where I charge the batteries….also get one with a louder alarm.

I was literally shaking when I saw that I had a fire in the garage. I could not believe I had forgotten that it was charging. This is why the “safety Nazi” should be put in from of the firing line. In a moment’s forgetfulness of all the habits I have been preaching about for the last year and a half I put my family at risk. I just hope my story will convince some of you develop and maintain the safe discipline of LiPoly charging. I also hope you will start “demanding” that your suppliers look into getting the newly arriving LiPoly and LiIon that have highly reduced fire potential.

Any comments and ridicule that my fellow flyers wish to pass my way I will humbly accept.

Crazy Ted -- in need of habit reinforcement
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Old Jan 17, 2005, 11:18 PM
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Mark Wood's Avatar
United States, CA, Bear Valley Springs
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As you wish but it could happen to any of us:

mw
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Old Jan 17, 2005, 11:42 PM
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Gig Harbor, Washington, United States
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WOW.

Thanks Ted.

I have gotten sloppy and frogetfull a few times myself. So far I have been lucky enough NOT to have any kind of fire or problem.

This is a good wakeup call for all of us.

I am very glad you got off without any major damage or injuries!

Larry
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Old Jan 17, 2005, 11:46 PM
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Gig Harbor, Washington, United States
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By hte way, I have a Hyalec CCCV supply also. The 50 volts unit.

I have noticed that it also will sometimes creep up the voltage when its first turned on.

I use it to charge larger packs and it only climbs .1 volts or so. I am supprised at the large change you had.

Larry

I have gotten in the habit of turning it on and letting it warm up for several minutes before I start charging.
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Old Jan 18, 2005, 12:24 AM
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Los Angeles, CA (UCLA)
Joined Nov 2002
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a good lesson. everyone can be sloppy just once. lucky you were prepared. if I have to leave the lipo charging for any amount of time, I used to use cooking dishes/pots like that. but now I never do that. I go to a field with uncharged batteries and sit beside them. may be a little over over cautious but better safe then sorry.

r
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Old Jan 18, 2005, 01:35 AM
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Switzerland, near Zuerich
Joined Mar 2004
171 Posts
Fine setting of the output voltage

Quote:
Originally Posted by tjcooper
LiPoly users,
Crazy Ted a.k.a. the 'safety Nazi' -- has been taken to the LiPoly "fire"ing line.

Just when you think you are a "safe player" you let down your guard. Last night I had two failures: one mental and one electronic.

I had a newly delivered single cell . . . . . . . . . . . . . . . . .e. I had the new 18VDC at 3 amp power supply that has been discussed on this forum. I had used it three or four times to charge known good packs and it performed well as a CV/CC power supply. The only shortcoming that the new power supply has is that the voltage control is rather twitchy to set to 4.2 volts (the last digit is hard to set easily by single digit moves). ............................................
Any comments and ridicule that my fellow flyers wish to pass my way I will humbly accept.
Crazy Ted -- in need of habit reinforcement
Ted , I'm happy to hear that no big loss happend for you - but you gave a strong lesson to all of us, not to get sloppy at anytime with LiPo safety

In your cheap powersupply the resolution and stability of the potentiometer is just not fine and time / temp stable enough what is needed to get
- if you have any chance, pls exchange the coarse poti against a Multiturn Potentiometer like :
http://www.potentiometers.com/MH20.c...05011802135323

just my 2cents

Meinolph
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Old Jan 18, 2005, 01:45 AM
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San Jose, CA
Joined Jun 2002
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Glad to hear that you did not suffer any fires. Thanks for the warnings. Makes me glad that I only charge Li-pos with an Astroflight 109, have left it on for many hours just to watch to see that it would stay stable and stay shut off. Gud Flying..........Dick
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Old Jan 18, 2005, 01:56 AM
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United States of America For Which We Stand!
Joined Jan 2004
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Glad everything went ok Ted. I take it that you mean this as a warning?

This is why I never...never as in ***not ever*** leave a battery on charge unless I'm right there with it. No exceptions! No barking dogs, no telephone ringing, no knocks on the door, nothing. If I have rto take more than 3 steps away from one, I unplug it.

I also never attempt to revive packs. It is impossible to reverse irreversable damage. Once a pack has been discharged below 3volts/cell it is permently damaged, and gets disposed of like all other packs that have gone to the angels...a salt water bath.

I also got a kick out of some of the posts saying it can happen to any of us. I sure hope not! It'll never happen to me, becasue I'll never ever ever trust one out of my sight, and I'll never get complacent about it, and that does mean never. Every single time I go near one, I think to myself "pay attention to what you're doing, and don't burn yourself and your planes up". I have a shop full of planes, and years and years worth of accumulated hobby related stuff. I cannot afford for a battery to cost me all of that. I don't care if the battery was 1000 dollars, if it was damaged, it would go into the salt water bath.

None of these batteries are worth risking a fire. Not even a 10S5P monster. I'm soooo glad you and your stuff is ok. I'm no safety Nazi...I'm just darn careful so i never have to hear it from one!
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Old Jan 18, 2005, 05:51 AM
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Backwoods Alabama
Joined May 2000
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Whew. This goes to show that you cannot let your guard down, ever. With Lipos, complacency is the killer.

Of all the Lipo crash-and-burn stories I've heard, this one needs to be stickied.

--Bill
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Old Jan 18, 2005, 06:40 AM
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Quote:
Originally Posted by tjcooper
... Any comments ... that my fellow flyers wish to pass my way...
tj,

I've noted and published that the voltage drifts upwardly on my inexpensive Chinese-made CC/CV, but I have a higher capability 30/20, and I haven't found it to drift nearly as much as yours - on the other hand, I haven't let it charge a LiPo beyond C/10, maybe two hours or so, at the most. I use a DVM "permantly" connected, to monitor voltage and twiddle the voltage fine control knob to keep it where I want it. Incidentally, the flexibility of Sermos connectors comes in handy here; I squeeze down the wire insert ferrule to fit my DVM probe tightly and "Y" a pair of the modified Sermoses in the charger leads. I monitor current with a Sears clamp-on ammeter.

Re the smoke detection question: If you look at the two tests of the Brinks box, the unsmothered "hot" fire produced almost no visible smoke. Your fire, judging by the evidence observed the following morning, was a hot one - which would be expected in an open dish. I'm hopeful that an upcoming test of what amounts to a little woodstove, made out of an ammo box without an air intake but with a flexible chimney routed outside through a window, can prevent collateral damage from LiPo accidents. We'll see.

A sigh of relief here - Nobody knows better than you that you got away lightly. I'm thankful for that.

Best regards,

- RD
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Old Jan 18, 2005, 08:11 AM
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Walled Lake, MI, USA
Joined Feb 2000
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Ted, obviously we are all relieved to learn that you dodged the bullet on this one. And, as always, it takes courage to post about making a mistake with Li cells because the critics are bound to sound off.

EDIT: My original remarks here criticized Ted for charging in an open dish. However, Ted had already addressed this in the lessons learned part of the original message in a point that I had overlooked:

"3) Put the sand bag on top of the cell (I had one sitting there and did not place it on because I was using the tiny push-clips and the bag might have disconnected them). Poor judgement call."

From this it's obvious that the dish is only one part of Ted's normal Li charging containment system. I should have known that Ted knew better than to make a regular habit of charging Li cells in an open dish. The open dish with sand bag on top of the cell is a safe system. The open dish without the sand bag is not safe.

It is never safe to charge Li cells in an open dish alone. We've had reports on this forum of the venting process causing burning cells to move around, and many users have also reported a shower of burning embers falling on items nearby. It's fortunate that this did not ignite nearby combustible materials this time.
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Old Jan 18, 2005, 08:20 AM
Random Flier
Oxford (UK) and Mtn View CA (USA)
Joined Nov 2002
1,403 Posts
Ted - glad to hear there was minimum damage done. Thanks for posting (again).

The lessons I take from this:
- Good to hear the "bowl" contained most of the fire (so it seems). [check: use Pyrex for my charging]
- CC/CV power supplies as chargers may not be infallible [check: use a Triton only so no issue for me; of course, a Triton isn't necessarily infallible ]
- LiPo experimentation eg with dead cells requires *more* vigilence [check: not needed to try this yet]
- smoke alarm over battery store [a retired microwave oven] / charger [action: need to get].

Browsing this forum is useful for its regular reports of, and thence reminders of, LiPo-safety habits!
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Old Jan 18, 2005, 08:25 AM
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Birmingham, AL
Joined Aug 2003
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Manohman you are fortunate Ted. For what it's worth, this is the charge system I use in my shop. I don't need to worry about portability because I charge in the open when at the field. But it has the ability to contain and hopefully snuff out a fire. I also have a smoke detector directly above the station in the shop/garage. I pray I never have to use it. Thank you for the tip about using a timer. I hadn't considered that, so I will steal one from the wifey's kitchen today!

Charge Station webpage,click here


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Old Jan 18, 2005, 09:05 AM
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Rochester, MN
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That's about scary as scary gets. I am glad that you and your family are safe. The procedures you mentioned seem to be pretty thorough with the only variable being the possible failure of the equipment and one little mental slip of the imperfect human (all of us).

Just as when I thought that the lithium technology was getting safer due to improved charging capabilities and experience gained, this happens. I guess i'll have to wait a little more since the consequences of a possible mistake are unbearable for me.
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Old Jan 18, 2005, 09:14 AM
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USA, TX, Weatherford
Joined Sep 2003
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thank goodness you and your family are safe..

i had a bad experience as well..i did not know that these things seem to "smell" tasty to dogs etc...

my dog decided that he would chew onone, and strangly enough, he was able to get one off of the table and went to chompin..!

fortunately, he was not burned, but the pillow and couch he was laying on certainly had problems...the 2S 1200 kind of burned down into a feather pillow that the dog called his, and then "singed" my leather couch and filled the house with a lovely sickly/sweet smoke...

scared the hell outta me...and still does to this day...i take a lot of care now with these cells...

again..am very glad you and your family are fine...

sincerely,

birdie
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