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Old Sep 02, 2004, 11:54 PM
Unsafe at any speed
Wiseguy's Avatar
Rochester, NY
Joined Jun 2003
442 Posts
Help!
Just a little punctured, it's still good!

So I've been flying (read: beating the foam out of) my little scram-blur j250 which flies (read: crashes) on some etec 2s 1200 packs that I've had around for quite a while. I've ejected the battery from its little velcro strip many times in my epic adventures with this plane, and today I was bringing them back in after smashing it around some more and noticed a very small puncture in one cell after I started charging it. It was sitting in the fire safe with my other ones...I had convinced myself that one pack was a little squished and I thought I flattened it back out with my hand...I thought it might explode so I was keeping a close eye on it...I should note, I think these are two different packs I'm talking about.

So I kept charging the punctured pack just to see what would happen....and nothing did. It kept its voltage like a champ and charged up happily on my shulze 330d, and I tucked it away in the fire safe and left it alone for a long time and still no problems.

Now, is this really a time bomb with a very short fuse? Or is it possible to have a tiny tear in the metal pouch without completely endangering the entire world? And I know lots of people are VERY skittish with li-poly packs (not without reason) but I want to get the most accurate assessment of this situation that I can...I'll add the fear and hype myself

Thanks!

-Josh
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Old Sep 03, 2004, 12:51 AM
Always right
Hovertime's Avatar
Chicago
Joined Feb 2003
5,924 Posts
I would like to know the ending of this story
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Old Sep 03, 2004, 03:27 AM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,449 Posts
You can't be "a little pregnant".
The pack has been compromised because the vacuum in that cell has been lost.
Proceed with caution.

mw
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Old Sep 03, 2004, 08:59 AM
Registered User
Walled Lake, MI, USA
Joined Feb 2000
11,182 Posts
There's not a large body of experience with extended use of damaged Li-polys because most people stop using them after they're damaged due to all of the catastrophic failures that have been reported with damaged cells. You're essentially playing Russian roulette. No one will be able to give you an absolutely definitive answer because no one can predict when the hammer is going to fall on the chamber with the bullet in it. Statistically speaking, you could get away with using it for many months, or it could fail within a day. The only guarantee is that you are operating at an elevated level of risk when continuing to use a damaged cell.
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Old Sep 03, 2004, 11:40 AM
Convert!
rroback's Avatar
Los Angeles, CA (UCLA)
Joined Nov 2002
3,889 Posts
20 dollar pack or house? which is more valuable. personally, if it works right now, I'd say it should keep working. but if it were mine, it would get the salt bath treatment ( aka death).

Rhett
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Old Sep 03, 2004, 12:57 PM
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SharksTooth's Avatar
United States of America For Which We Stand!
Joined Jan 2004
1,346 Posts
A little punctured means a little destroyed. The pack is finished. If you want to play, I would play outside, becasue I gurantee you that pack will go ballooned and will probably catch on fire. There are mnay who have tried to "revive" destroyed packs to no avail on here. These packs are NOT damaged...they are destroyed. Put them in a salt water bath before they hurt you, or destroy your shop or house. These things are not to be played with. The pack has lost vacuum, and is therefore finished. You cannot put the vacuum back.
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Old Sep 03, 2004, 01:00 PM
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San Jose Ca / RSA flyer
Joined May 2003
8,030 Posts
The punctured cell will always be out of balanced because of lost capacity. U can never charge the pack and expect the 2 cells to be the same. Eventually the good cell will charge above 4.2V and balloon. U must remove the bad cell in the pack and replace with a normal cell of the same type if U want to continue using the pack.

U can only dispose the bad cell. Wasting time charging the bad cell.

I had a Kokam 1500 3S1P pack with a punctured cell. It worked fine for a while. When I checked the bad cell after each flight the voltage would always be lower than the 2 good ones even when I charged the bad cell higher than other 2 good ones.
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Old Sep 03, 2004, 01:11 PM
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Sunnyvale Ca
Joined Jun 2002
1,006 Posts
WiseGuy,
you can restore the vaccum by using one of those food saver vaccum packs, but it is a less than perfect vaccum. But that leaves the question of how to seal that pack after you have pulled a good vacuum on it (beware of the sickly sweet smelling electrolyte smell that comes out....it has some bad things for the lungs in it!). Perhaps you could have a piece of tape held appart with toothpicks over the hole while evacuating the pouch, and then you pull the toothpicks out of the plastic sack overcovering to make a seal....and they use hot glue to finish the job when you remove the LiPoly from the overcovering.

But wait....there is more fun ahead! Since you have already charged your packs with a puncture present. There has probably been a "change of state" of the graphite matrix inside the pouch. It changes from a midnight black to a brown-gray black....and the efficiency of the cells drop by around 10-50% depending on how big is the area and how many charges you have done. Bottom line, the cells are going to go downhill once you have punctured and recharged them....it is the chemical nature of the beast.

And add to that the thrill of fireworks in your garage or plane.....the adventure just keeps getting better!

BOTTOM LINE: get your cheap thrills in a movie theater. Discard the punctured pack safely (salt water immersion) and get another pack. These LiPoly's can act so nice and friendly under most circumstances, but when they "turn on you" they have real teeth that can do serious damage.

Crazy Ted -- a battery junkie
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Old Sep 03, 2004, 01:38 PM
Unsafe at any speed
Wiseguy's Avatar
Rochester, NY
Joined Jun 2003
442 Posts
Since I only have one fireproof container, and it currently holds all of my batteries, I think I'll give this pack the salty bath and call it a tour of duty. Thanks everyone! I wasn't sure if it kept working that meant everything was okay or not...but if these things are going to go straight downhill with any puncture, I think it's best I not play with it in my dorm room (WAY more stuff in here than any house!)

...and now to find some salt.

-Josh
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Old Sep 03, 2004, 02:51 PM
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San Jose Ca / RSA flyer
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send them to me

Hall Woo
2681 Monterry Rd #463
san Jose Ca 95111

We'll blown them up
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Old Sep 03, 2004, 05:01 PM
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gtstubbs's Avatar
Perth Westen Australia
Joined Jun 2003
443 Posts
Quote:
Originally Posted by hall woo
send them to me

Hall Woo
2681 Monterry Rd #463
san Jose Ca 95111

We'll blown them up
Punctured, Charged? pack through the mail, is that a good idea?
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Old Sep 03, 2004, 05:11 PM
Unsafe at any speed
Wiseguy's Avatar
Rochester, NY
Joined Jun 2003
442 Posts
Yeah, I'm not sure sending time bomb lipo's through the mail is going to make the USPS very happy. Besides, I'm a college student...I'm good at blowing things up myself
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Old Sep 03, 2004, 05:36 PM
idk
ripper69's Avatar
Inver Grove Heights ,MN
Joined Jul 2004
490 Posts
Be very carefull, this is what happens when you puncture a cell:
vid here
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Old Sep 03, 2004, 11:00 PM
Unsafe at any speed
Wiseguy's Avatar
Rochester, NY
Joined Jun 2003
442 Posts
Ooh, that is scary. I guess I was lucky when mine got a hole in it then...since it didn't explode in about 30 hours afterwards (before I started soaking it. Little bubbles have been coming out of the punctured hole in the salt water solution...looks like it's working!)
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Old Sep 06, 2004, 03:54 AM
Dude! Sweet!
Santa Maria, California
Joined Sep 2004
65 Posts
I started putting the battery on sideways on the top of my Scram-Blur. I was worried about smashing the end in a crash. I've bounced it a couple of times since and the battery just ejects and looks fine. I do watch that battery pretty close. I've not noticed any change in the flight characteristics with the battery mounted sideways.

Dave
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