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Old Mar 21, 2005, 03:28 PM
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hybris's Avatar
Houston, TX
Joined May 2003
744 Posts
Be careful with the Deans micro polarized.

I fried my first lipo due to user error. I have been flying lipos for 3 years now and never had a problem. I just finished a lunchtime micro-heli flight, unplugged the battery and put the heli in the back of my car. I usually store the battery in a fireproof container, but not this time. A couple of seconds later, I saw smoke! Grabbed the heli and pulled the battery off. The connector was fried. The pin on the esc shorted between the battery's pin and socket. Melted the connector slightly and now the battery was too hot to touch. Too bad, it was an almost new Apogee 1050 3s. I let it sit for a couple of minutes but it is still hot. I thought I saw the smoke coming from the battery (tabs probably) so I think I will retire it.

Two things can be learned from this experience. Always remove the battery from the aircraft and be careful with those Deans micro polarized connectors. I think I will put the little rubber caps (screw protectors) over the battery connectors from now on. I just thought I would share this and I am happy I only lost a battery. I don't want to start a panic, just be precautious.
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Old Mar 21, 2005, 03:35 PM
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Kalamazoo, MI USA
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Thanks for sharing that. I was not aware of the possibility. Good reason to store the batteries separate from each other too.
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Old Mar 21, 2005, 03:41 PM
Cal
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San Gabriel, California
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Wow.........Hybris, can you explain what happened again, possibly in a different way. I'd like to totally understand what happened and I'm not real clear on it. I use Micro Deans exclusivly. Thanks.......
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Old Mar 21, 2005, 03:54 PM
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Houston, TX
Joined May 2003
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Yes, I do normally store the batteries separate from one another.

Let me try to explain it better. The battery has a pin and a socket (male and female). The pin on the speed controller's plug aligned perfectly to touch the socket at a 45 degree angle and come in contact with the pin on the battery. I will post a picture later. I think I read about this somewhere else on the groups.
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Old Mar 21, 2005, 04:09 PM
ElectriGlo Pilot
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Ashburn, Virginia, United States
Joined Dec 2003
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Wow, thats one in at least a few thousand that the ESC pin would come to rest like that! But I guess anything's possible.

I read here where someone soldering deans onto a battery used the "plug in the other deans to keep things straight and easy to plug later" trick and used metal alligator clips to hold while he soldered. The plastic connector slipped out of the metal alligator clip which then grabbed the exposed pins and shorted it. I think that case was momentary and no permanent damage but still something else to consider.
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Old Mar 21, 2005, 04:18 PM
Cal
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San Gabriel, California
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Quote:
Originally Posted by hybris
Yes, I do normally store the batteries separate from one another.

Let me try to explain it better. The battery has a pin and a socket (male and female). The pin on the speed controller's plug aligned perfectly to touch the socket at a 45 degree angle and come in contact with the pin on the battery. I will post a picture later. I think I read about this somewhere else on the groups.
Thanks, hybris.......I understand perfectly now. No picture required. I did that once when I was soldering some micros on the battery......Got a few sparks for a second.............

I will make sure that I take my batts off my planes before I transport them from now on........Thanks again......
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Old Mar 21, 2005, 04:24 PM
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Houston, TX
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I went and checked on the battery. It is cool now and no apparent damage/ballooning. But a spectator and I did see smoke from the tab end. The tab probably got hot and melted some of the insulation; I will dispose of it for safety.
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Old Mar 21, 2005, 05:17 PM
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Ohio
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Glad your heli/car was ok.

Here is a thread with protection ideas.

http://www.rcgroups.com/forums/showthread.php?t=186078

It only takes a small pin to short the battery; like your ESC pin or a "T" pin in your flight bag.

Ed
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Old Mar 21, 2005, 05:43 PM
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Houston, TX
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I will do something like this. It will be nice to have different colors for charged or not.
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Old Mar 21, 2005, 06:30 PM
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Pasadena, CA
Joined Dec 2003
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Don't feel too bad Hybris. I once cut my lipo pack's wires to make them shorter... at the same time. No damage, though because contact was brief, but I could feel the warmth in the wires. That hurt my pride more than anything else.
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Old Mar 21, 2005, 07:55 PM
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Houston, TX
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Well here are the pictures after the NTSB investigation. This is how they shorted (evidence from the scorch marks).
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Old Mar 21, 2005, 08:45 PM
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Walled Lake, MI, USA
Joined Feb 2000
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Quote:
Originally Posted by hybris
I usually store the battery in a fireproof container, but not this time.
This seems to be a more common pattern in recent LiPo accident reports. People who understand the risks of LiPos and normally take all of the generally accepted safeguards briefly relax their guard and get bitten. This is different from many of the early LiPo accident reports, where people just didn't know all of the risks.

In any case, it's really good to know that you got away without paying too high a price, and that you shared it here so that others could learn. Thanks for taking the time to share this.
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Old Mar 21, 2005, 09:08 PM
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hoppy's Avatar
Space Coast
Joined Oct 2000
20,720 Posts
hybris,
Thanks for the heads up. I've been getting lax with letting my battery leads fall where they may in the battery transport box. I think I'll add a lead capture device of some sort that will keep them separated. Perhaps a piece of foam with slits one inch apart through which the leads are pushed into.
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Old Mar 21, 2005, 09:19 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
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Thread savers for battery leads

Thought it timely to toss this one in here!

Different sizes for different MPJ Gold Connectors.

Cheers, Phil
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Old Mar 21, 2005, 10:05 PM
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everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
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Possible accidents such as this is why I refuse to use a male connector(with exposed contacts) on a battery. The Deans Micro Plug 4R P.N. 1242 is a four connector of typical Deans high quality and if you use two contacts for each lead you double the current capability. These also work well for ESC to motor connections on smaller BL motors. I guess there is no full proof connectors with the possible exception of APPs.

Charles
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